STM32CubeMX+MDK通过I2S接口进行音频输入输出（全双工读写一个DMA回调）

一、前言

目前有一个关于通过STM32F411CEUx的I2S总线接口控制SSS1700芯片进行音频输入输出的研究。
SSS1700 是具有片上振荡器的 3S 高度集成的USB音频控制器芯片。 SSS1700 功能支持96 KHz 24 位采样率，带外部音频编解码器（24 位/96KHz I2S 输入和输出）并具有内置立体声16/24位ADC、立体声16/24位DAC、耳机驱动、五段硬件均衡器、音频 PLL、USB 时钟振荡器和 USB FS 控制器加上 PHY。（实际个人认为使用基于蓝牙的音频控制芯片来结合STM32等单片机的方案可能更加方便一些，基于USB接口的耳机音响等基本已经退出舞台了，因此使用该类usb芯片个人不是很理解，但也有可能蓝牙被做它用，USB可以通过hub扩展，而蓝牙不容易扩展，具体原因暂时不得而知）
整体的逻辑比较简单：

手机通过usb接口将音频数据传输给SSS1700音频芯片，该芯片提供I2S接口，我们MCU通过I2S接口读取该芯片中的音频数据达到录音的效果；
如果手机没有放音时，我们MCU通过I2S接口向该音频芯片写入音频内容达到放音的效果。

待验证的扩展功能：

音频芯片通过I2S接口读取音频数据的同时是否还可同时通过其它接口读取？
手机通过usb接入音频芯片放音时我们是否可以通过I2S接口同步控制音频芯片放音？这个过程理论上芯片是被占用的，是否能像电脑音频混音播放还需要实验一下。

二、资料收集

官方i2s例子：https://www.stmcu.com.cn/Designresource/detail/LAT/710151
https://community.st.com/t5/stm32-mcus-products/pcm-sound-to-pc-gt-stm32f4-microphone/td-p/464908
https://www.st.com/en/embedded-software/stm32cubef4.html#get-software
参考官方HAL库的示例：en.stm32cubef4-v1-28-0\STM32Cube_FW_F4_V1.28.0\Projects\STM32F411E-Discovery\Applications\Audio\Audio_playback_and_record\Src\waveplayer.c
sss1700：https://www.bilibili.com/read/cv21981976/
i2s理解：https://blog.csdn.net/wholetus/article/details/109326191
音频及采样频率：https://zhuanlan.zhihu.com/p/101073274
ST-LINK及JLINK等：https://zhuanlan.zhihu.com/p/454940732
stm32 usb虚拟串口收发：https://blog.csdn.net/m0_60876665/article/details/122788442
i2s读取录音的重点参考：https://blog.csdn.net/weixin_44226356/article/details/125153210
i2s读取的数据发送上位机测试参考：https://www.cnblogs.com/pingwen/p/11794081.html
pcm、pdm：https://blog.csdn.net/u010783226/article/details/130850834
FATFS追加写入：https://blog.csdn.net/ba_wang_mao/article/details/109464436
缓存机制：https://www.cnblogs.com/puyu9499/p/15914090.html
DMA双缓存（比较常见的DMA缓存方式，但是个人更推荐上面缓存机制方式，代码改动小，好理解）：https://blog.csdn.net/weixin_43336331/article/details/110481985
放音测试参考（测试i2s放音时可以接一个类似设备去听声音）：https://blog.csdn.net/sudaroot/article/details/106834893
全双工参考（但是其没有使用DMA回调方式）：https://blog.csdn.net/zwl1584671413/article/details/86650062
busy问题：https://blog.csdn.net/qq_42254853/article/details/130145214
全双工阻塞方式及异步回调方式使用启发：https://community.st.com/t5/stm32-mcus-products/stm32f411-hal-driver-i2s-full-duplex-ext-sd-issue/td-p/442735

三、I2S接口理解

1、基础概念

I2S(Inter-IC Sound)总线, 又称集成电路内置音频总线，是飞利浦半导体公司(现为恩智浦半导体公司)针对数字音频设备之间的音频数据传输而制定的一种总线标准。该总线专门用于音频设备之间的数据传输，广泛应用于各种多媒体系统。
它为音频应用而设计，是一种电子的串行总线，用于连接电子音频设备。
它传输的是PCM音频数据（即脉冲编码调制)，PCM音频数据是未经压缩的音频采样数据裸流，它是由模拟信号经过采样、量化、编码转换成的标准数字音频数据。I2S是音频数字化后数据排列的一种格式。
声音数字化过程：

转为 PCM 格式三个参数：

声道数、采样位数和采样频率。

采样频率：每秒钟取得声音样本的次数。采样频率越高，声音质量越好，还原越真实，但同时它占的资源比较多。
采样位数：每个采样点用多少二进制位表示数据范围。量化位数越多，音质越好，数据量也越大。
声道数：使用声音通道的个数，有单声道和立体声之分，立体声比单声道数据量翻倍。
音频数据量＝采样频率×量化位数×声道数/8(字节/秒)

由于PCM数据量比较大，所以一般应用过程中还会对PCM数据进行编码后传输，在播放时再解码（编解码会造成音质损失）。

2、信号线

I2S协议只定义三根信号线：时钟信号SCK、数据信号SD和左右声道选择信号WS。

时钟信号 Serial Clock

SCK是模块内的同步信号，从模式时由外部提供，主模式时由模块内部自己产生。 不同厂家的芯片型号，时钟信号叫法可能不同，也可能称BCLK/Bit Clock或SCL/Serial Clock

数据信号 Serial Data

**SD是串行数据，在I2S中以二进制补码的形式在数据线上传输。**在WS变化后的第一个SCK脉冲，先传输最高位（MSB, Most Significant Bit）。先传送MSB是因为发送设备和接收设备的字长可能不同，当系统字长比数据发送端字长长的时候，数据传输就会出现截断的现象/Truncated，即如果数据接收端接收的数据位比它规定的字长长的话，那么规定字长最低位（LSB: Least Significant Bit）以后的所有位将会被忽略。如果接收的字长比它规定的字长短，那么空余出来的位将会以0填补。通过这种方式可以使音频信号的最高有效位得到传输，从而保证最好的听觉效果。
√ 根据输入或输出特性，不同芯片上的SD也可能称SDATA、SDIN、SDOUT、DACDAT、ADCDAT等； √ 数据发送既可以同步于SCK的上升沿，也可以是下降沿，但接收设备在SCK的上升沿采样，发送数据时序需考虑

左右声道选择信号 Word Select

WS是声道选择信号，表明数据发送端所选择的声道。 当：
√ WS＝0，表示选择左声道 √ WS＝1，表示选择右声道
WS也称帧时钟，即LRCLK/Left Right Clock。 WS频率等于声音的采样率。WS既可以在SCK的上升沿，也可以在SCK的下降沿变化。从设备在SCK的上升沿采样WS信号。数据信号MSB在WS改变后的第二个时钟（SCK）上升沿有效（即延迟一个SCK），这样可以让从设备有足够的时间以存储当前接收的数据，并准备好接收下一组数据。
另外，有时为使系统间更好地同步，还要传输一个主时钟(MCK)，STM32F429x系列控制器固定输出为256* FS。

3、半/全双工及主/从模式

支持全双工和半双工通信。(单工数据传输只支持数据在一个方向上传输；半双工数据传输允许数据在两个方向上传输，但是在某一时刻，只允许数据在一个方向上传输，它实际上是一种切换方向的单工通信；全双工数据通信允许数据同时在两个方向上传输，因此，全双工通信是两个单工通信方式的结合，它要求发送设备和接收设备都有独立的接收和发送能力。
支持主/从模式。(主模式：就是主CPU作为主机，向从机（挂载器件）发送接收数据。从模式：就是主CPU作为从机，接收和发送主机（挂载器件）数据。而主从机的分别其实是一个触发的作用，主机主动触发，从机只能被动响应触发。)

四、STM32CubeMX配置

1、配置RCC

根据开发板的晶振配置高速和低速时钟（查看原理图确认对应引脚是否已经配置了对应的晶振）：

2、配置系统调试接口

我这里的板子为JTAG的SWD下载口

3、配置I2S

根据音频芯片及功能，这里暂时配置为全双工从模式，接收音频数据及发送音频数据，参数和音频芯片测试板配置的一致，不开启主时钟输出看一下是否存在干扰，如果干扰造成噪声等再开启主时钟试一下。
根据官方的说明：Transmission Mode: 传输模式。决定 SD 数据线传输方向（SD_Ext 方向相反）。所以如果设置了Transmit那么SD就是发送，SD_Ext就是接收，反之设置了Receive那么SD就是接收，SD_Ext就是发送。
这个对接线很有帮助，只是软件开发接口不关心，全双工时收发触发及回调都各自只需要一个接口。
Communication Standard: 传输标准。本文中采用 I2S Philips 标准（需要和音频芯片相同标准）。
Data and Frame Format: 数据位宽和帧位宽。如同“传输标准”的配置，保持与编解码器配置一致。
Selected Audio Frequency: 音频频率。可选频率 8KHz、11KHz、16KHz、22KHz、32KHz、44KHz、48KHz、96KHz、192KHz，这里选择 48KHz。如同“传输标准”的配置，保持与编解码器配置一致。
Clock polarity:时钟极性（非激活态时）。

4、配置I2S DMA

根据官网的I2S音频开发介绍，这里配置添加两个DMA，具体如下，推荐Half World，模式推荐循环模式，这样好配合非阻塞回调函数，正常模式更适合阻塞方式处理，但阻塞模式往往速度比较慢，高采样率时丢采样数据的情况比较多：

5、配置USB作为虚拟串口

我这里的STM32F411CEUx具备USB口，时钟配置好后USB也是可以配置的，这个usb口目前开发板是type-c的，不太好接U盘和SD卡了，所以用来配置作为一个虚拟串口和上位机通信（后续换了F407ZET6，HS的USB速度更加快，外围接口较多，外挂U盘、SD卡、flash都可以拿来测试）：

配置USB DEVICE为虚拟串口：

6、增加一组串口2作为调试及外部交互用

默认配置即可：

7、时钟配置

时钟配置那里点击解决时钟问题就会自动配置了，不配置外部晶振时钟的话这里USB是没有办法使用的：

推荐的F4xx的i2s时钟配置（最后的音质调整具体进行了说明）：

8、配置heap和stack

适当调高heap和stack，我们后面使用的fifo缓存使用malloc需要的heap较大。

之后生成代码即可。

五、MDK配置及程序

1、MDK配置

1.用keil打开STM32F411的程序，结果提示下面的问题，就是没有安装固件库，会自动跳转去安装，这个方式往往下载不成功，我们去官网手动下载安装：

2.然后去keil官网下载对应的固件库，官网地址：https://www.keil.com/

3.然后搜索对应的芯片类型，比如我这个就是STM32F411CEUx

下载对应pack即可：

4.安装对应下载的xxx.pack，并且目录直接默认是keil安装的目录。

5.安装之后再次打开keil就不会报错了，可以看到已经安装的固件库

6.JLINK+SW配置（也有可能是ST-LINK等，根据具体板子配置即可）

点击魔法棒，选择Debug，使用J-LINK/J-TRACE Cortex：

之后设置SW端口并scan即可：

然后就可以下载以及debug调试程序了。

2、代码

测试时逻辑比较简单，对于录音：电脑端播放音频通过usb口传给音频测试板，mcu通过I2S接口读取音频内容，再通过usb的模拟串口连接并发送到电脑，在电脑的串口工具中存储接收到的二进制数据存储到文件中，通过工具播放pcm数据。对于放音：将之前的pcm数据获取一部分写死到程序数组中，程序运行时就开始调用I2S接口写入音频芯片，然后在电脑端听声音。（实际使用时会通过外部flash存储音频数据，后续会简单总结spi flash读写）

2.1 转换16进制的hex为pcm并进行播放（可以不需要，直接通过写入原始字节数据到文件后导入播放器播放）

# -*- coding:utf-8 -*-
from scipy import signal
import numpy as np
import matplotlib.pyplot  as pltimport matplotlib
myfont = matplotlib.font_manager.FontProperties(fname='C:\\Windows\\Fonts\\cambria.ttc')filename = r'data.pcm'
filepath = r'.'f = open(filepath + '\\' + filename)
if 0:  # 这是ascii保存的数据格式line = f.read()data = [l.split(' ')[-1] for l in line.split('\n') if l]data = [int(x) for x in data]
else: # 这是HEX保存的数据格式line = f.read()[:-1]print("buffer count", len(line))data0 = np.array([int(x, base=16) for x in line.split(' ')])data_1 = data0[0:len(data0):2]data_2 = data0[1:len(data0):2]data3 = data_2 * 0x100 + data_1
# data = np.frombuffer(data3, dtype=np.int16)
data = data3.astype(np.int16)filename2 = filename + "_ascii.pcm"
f=open(filepath + '\\' + filename2, 'w')
np.savetxt(f, data, fmt="%i", newline='\n')import sounddevice as sd
fs = 16000
src = data
sd.play(1*src/np.max(src), fs, blocking=True)

2.2 python接收串口数据直接写入到文件（i2s接收的音频数据通过串口转发出来）

import serialdef bytes2Hex(argv):  # 十六进制显示 方法1try:result = ''hLen = len(argv)for i in range(hLen):hvol = argv[i]hhex = '%02x ' % hvolresult += hhexexcept:passreturn resultdef read_com():portx = "COM23"bps = 12000000try:ser = serial.Serial(portx, bps)print("串口详情参数：", ser)with open("data.pcm", "wb") as binary_file:while ser.isOpen():data = ser.read(size=2)if data:binary_file.write(data)print(data)# num = ser.inWaiting()  # 查询串口接收字节数据，非阻塞# if num:#     line = ser.readline().decode()# line = ser.read(num)# content = bytes2Hex(line)# content = str(line)# content = str(line).strip('b').strip('\'')# f.write(line)# f.flush()# f.write(content)# print(line)except:passfinally:ser.close()binary_filef.close()if __name__ == "__main__":read_com()

2.3 python读取文件内容通过串口发送给stm32

import serialdef send_com():portx = "COM28"bps = 115200try:ser = serial.Serial(portx, bps)print("串口详情参数：", ser)with open("data.pcm", "rb") as binary_file:while ser.is_open:print("serieal open success")data = binary_file.read(4)if not data: breakprint(data)ser.write(data)except:passfinally:ser.close()binary_file.close()if __name__ == "__main__":send_com()

2.4 U盘状态判断（外挂U盘存储时使用）

printf("test...\n");HAL_Delay(1000);MX_USB_HOST_Process();HAL_Delay(1000);/* USER CODE BEGIN 3 *///判断USB是否进入准备状态APPLICATION_READYswitch(Appli_state){/*** The generated code from STM32CubeMX has two "confusing" application states* APPLICATION_START on HOST_USER_CONNECTION and APPLICATION_READY on HOST_USER_CLASS_ACTIVE.* Any FatFs commands should be executed after APPLICATION_STATE_READY is reached."*/case APPLICATION_READY:printf("ready ok\n");MSC_Application();Appli_state = APPLICATION_IDLE;break;case APPLICATION_IDLE:default:break;}

2.5 FATFS文件操作（U盘读写文件时使用）

FATFS USBDISKFatFs;           /* File system object for USB disk logical drive */
FIL MyFile;                   /* File object */extern ApplicationTypeDef Appli_state;/*** @brief  Main routine for Mass Storage Class* @param  None* @retval None*/
//下面函数操作USB 文件读写，可根据需要修改，函数名可自定义
void MSC_Application(void) {/* FatFs function common result code description: *//*  FR_OK = 0,                (0) Succeeded *//*  FR_DISK_ERR,              (1) A hard error occurred in the low level disk I/O layer *//*  FR_INT_ERR,               (2) Assertion failed *//*  FR_NOT_READY,             (3) The physical drive cannot work *//*  FR_NO_FILE,               (4) Could not find the file *//*  FR_NO_PATH,               (5) Could not find the path *//*  FR_INVALID_NAME,          (6) The path name format is invalid *//*  FR_DENIED,                (7) Access denied due to prohibited access or directory full *//*  FR_EXIST,                 (8) Access denied due to prohibited access *//*  FR_INVALID_OBJECT,        (9) The file/directory object is invalid *//*  FR_WRITE_PROTECTED,       (10) The physical drive is write protected *//*  FR_INVALID_DRIVE,         (11) The logical drive number is invalid *//*  FR_NOT_ENABLED,           (12) The volume has no work area *//*  FR_NO_FILESYSTEM,         (13) There is no valid FAT volume *//*  FR_MKFS_ABORTED,          (14) The f_mkfs() aborted due to any parameter error *//*  FR_TIMEOUT,               (15) Could not get a grant to access the volume within defined period *//*  FR_LOCKED,                (16) The operation is rejected according to thex file sharing policy *//*  FR_NOT_ENOUGH_CORE,       (17) LFN working buffer could not be allocated *//*  FR_TOO_MANY_OPEN_FILES,   (18) Number of open files > _FS_SHARE *//*  FR_INVALID_PARAMETER      (19) Given parameter is invalid */FRESULT res;                                          /* FatFs function common result code */uint32_t byteswritten, bytesread;                     /* File write/read counts */uint8_t wtext[] = "Hello Test USB!";                     /* File write buffer */uint8_t rtext[100];                                   /* File read buffer *//* Register the file system object to the FatFs module */res = f_mount(&USBDISKFatFs, (TCHAR const *) USBHPath, 0);if (res != FR_OK) {/* FatFs Initialization Error */USBH_UsrLog("f_mount error: %d", res);Error_Handler();}USBH_UsrLog("create the file in: %s", USBHPath);/* Create and Open a new text file object with write access */res = f_open(&MyFile, "USBHost.txt", FA_CREATE_ALWAYS | FA_WRITE);if (res != FR_OK) {/* 'hello.txt' file Open for write Error */USBH_UsrLog("f_open with write access error: %d", res);Error_Handler();}/* Write data to the text file */res = f_write(&MyFile, wtext, sizeof(wtext), (void *) &byteswritten);if ((byteswritten == 0) || (res != FR_OK)) {/* 'hello.txt' file Write or EOF Error */USBH_UsrLog("file write or EOF error: %d", res);Error_Handler();}/* Close the open text file */f_close(&MyFile);/* Open the text file object with read access */res = f_open(&MyFile, "USBHost.txt", FA_READ);if (res != FR_OK) {/* 'hello.txt' file Open for read Error */USBH_UsrLog("f_open with read access error: %d", res);Error_Handler();}/* Read data from the text file */res = f_read(&MyFile, rtext, sizeof(rtext), (void *) &bytesread);if ((bytesread == 0) || (res != FR_OK)) {/* 'hello.txt' file Read or EOF Error */USBH_UsrLog("f_read error: %d", res);Error_Handler();}/* Close the open text file */f_close(&MyFile);/* Compare read data with the expected data */if ((bytesread != byteswritten)) {/* Read data is different from the expected data */USBH_UsrLog("file doesn't match");Error_Handler();}/* Success of the demo: no error occurrence */USBH_UsrLog("USBHost.txt was created into the disk");/* Unlink the USB disk I/O driver */FATFS_UnLinkDriver(USBHPath);
}uint16_t dma[4] = {0};
uint8_t is_ready = 0;void HAL_I2S_RxCpltCallback(I2S_HandleTypeDef *hi2s)
{if(hi2s==&hi2s2){if (dma[0] || dma[1]) {if (is_ready) {FRESULT res;                                          /* FatFs function common result code *//* Create and Open a new text file object with write access */res = f_open(&MyFile, "data.pcm", FA_OPEN_EXISTING | FA_WRITE);if (res != FR_OK) {/* 'hello.txt' file Open for write Error */USBH_UsrLog("f_open with write access error: %d", res);Error_Handler();}/* 查找文件的结尾 */res = f_lseek(&MyFile, f_size(&MyFile));/* Write data to the text file */uint32_t byteswritten;printf("%02x%02x", dma[0], dma[1]);res = f_write(&MyFile, (uint8_t *) &dma, 2, (void *) &byteswritten);if ((byteswritten == 0) || (res != FR_OK)) {USBH_UsrLog("file write or EOF error: %d", res);Error_Handler();}f_close(&MyFile);}}}
}

switch (Appli_state) {/*** The generated code from STM32CubeMX has two "confusing" application states* APPLICATION_START on HOST_USER_CONNECTION and APPLICATION_READY on HOST_USER_CLASS_ACTIVE.* Any FatFs commands should be executed after APPLICATION_STATE_READY is reached."*/case APPLICATION_READY:printf("ready ok\n");
//                MSC_Application();FRESULT res;                                          /* FatFs function common result code *//* Register the file system object to the FatFs module */res = f_mount(&USBDISKFatFs, (TCHAR const *) USBHPath, 0);if (res != FR_OK) {/* FatFs Initialization Error */USBH_UsrLog("f_mount error: %d", res);Error_Handler();}USBH_UsrLog("create the file in: %s", USBHPath);/* Create and Open a new text file object with write access */res = f_open(&MyFile, "data.pcm", FA_CREATE_ALWAYS | FA_WRITE);if (res != FR_OK) {/* 'hello.txt' file Open for write Error */USBH_UsrLog("f_open with write access error: %d", res);Error_Handler();}f_close(&MyFile);HAL_I2S_Receive_DMA(&hi2s2, dma, sizeof(dma));Appli_state = APPLICATION_IDLE;is_ready = 1;break;case APPLICATION_IDLE:break;case APPLICATION_DISCONNECT:FATFS_UnLinkDriver(USBHPath);is_ready = 0;Appli_state = APPLICATION_IDLE;break;default:break;}

2.6 fifo缓存实现（解决i2s dma读写和存储读写时速度不对等问题）

//******************************************************************************************
//!
//! \file   FIFO.h
//! \brief  Genernal FIFO Model Interface.
//!         You can use uniform FIFO Model to manager Any type of data element.
//! \author cedar
//! \changed damom.li
//! \changed sky.huang
//! \date   2016-11-03
//! \email  xuesong5825718@gmail.com
//!
//! \version: 1.1 add fifo_s_gets_noprotect function
//!
//! Copyright (c) 2013 Cedar MIT License
//!
//! Permission is hereby granted, free of charge, to any person obtaining a copy
//! of this software and associated documentation files (the "Software"), to deal
//! in the Software without restriction, including without limitation the rights to
//! use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
//! the Software, and to permit persons to whom the Software is furnished to do so,
//! subject to the following conditions:
//!
//! The above copyright notice and this permission notice shall be included in all
//! copies or substantial portions of the Software.
//!
//! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//! IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//! FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//! AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//! LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//! OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
//! IN THE SOFTWARE.
///
//******************************************************************************************
#ifndef __FIFO_H__
#define __FIFO_H__
#ifdef __cplusplus
"C"
{
#endif#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>#define MUTEX_DECLARE(mutex) unsigned long mutex
#define MUTEX_INIT(mutex)    do{mutex = 0;}while(0)
#define MUTEX_LOCK(mutex)    do{__disable_irq();}while(0)
#define MUTEX_UNLOCK(mutex)  do{__enable_irq();}while(0)//******************************************************************************************//!                           CONFIGURE MACRO//******************************************************************************************#define FIFO_NDEBUG
#define USE_DYNAMIC_MEMORY //!< Use system malloc/free function//******************************************************************************************//!                     Macro Function//******************************************************************************************//******************************************************************************************//!                           PUBLIC TYPE//******************************************************************************************//! FIFO Memory Model (Single Byte Mode)typedef struct{char *p_start_addr; //!< FIFO Memory Pool Start Addresschar *p_end_addr;   //!< FIFO Memory Pool End Addressint free_num;       //!< The remain capacity of FIFOint used_num;       //!< The number of elements in FIFOchar *p_read_addr;  //!< FIFO Data Read Index Pointerchar *p_write_addr; //!< FIFO Data Write Index PointerMUTEX_DECLARE(mutex);} fifo_s_t;//! FIFO Memory Modeltypedef struct{char *p_start_addr; //!< FIFO Memory Pool Start Addresschar *p_end_addr;   //!< FIFO Memory Pool End Addressint free_num;       //!< The remain capacity of FIFOint used_num;       //!< The number of elements in FIFOint unit_size;      //!< FIFO Element Size(Unit: Byte)char *p_read_addr;  //!< FIFO Data Read Index Pointerchar *p_write_addr; //!< FIFO Data Write Index PointerMUTEX_DECLARE(mutex);} fifo_t;//******************************************************************************************//!                           PUBLIC API//******************************************************************************************#ifdef USE_DYNAMIC_MEMORY//******************************************************************************************////! \brief  Create An New FIFO Instance(in Single Mode).//! This function allocate enought room for N blocks fifo elements, then return the pointer//! of FIFO.//!//! \param  [in] uint_cnt is count of fifo elements.//! \retval The Pointer of FIFO instance, return NULL is failure to allocate memory.//!//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>//!            Header file before use this function.//! \note   -# Functions FIFO_Create and FIFO_Destory must be used in pairs.//!//******************************************************************************************fifo_s_t *fifo_s_create(int uint_cnt);//******************************************************************************************////! \brief  Destory FIFO Instance(in Single Mode).//!  This function release memory, then reinit the FIFO struct.//!//! \param  [in] p_fifo is the pointer of FIFO instance//! \retval None.//!//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>//!            Header file before use this function.////******************************************************************************************void fifo_s_destroy(fifo_s_t *p_fifo);#endif // USE_DYNAMIC_MEMORY//******************************************************************************************////! \brief  Initialize an static FIFO struct(in single mode).//!//! \param  [in] p_fifo is the pointer of valid FIFO instance.//! \param  [in] p_base_addr is the base address of pre-allocate memory, such as array.//! \param  [in] uint_cnt is count of fifo elements.//! \retval 0 if initialize successfully, otherwise return -1.////******************************************************************************************int fifo_s_init(fifo_s_t *p_fifo, void *p_base_addr, int uint_cnt);//******************************************************************************************////! \brief  Put an element into FIFO(in single mode).//!//! \param  [in]  p_fifo is the pointer of valid FIFO.//! \param  [in]  element is the data element you want to put//!//! \retval 0 if operate successfully, otherwise return -1.////******************************************************************************************int fifo_s_put(fifo_s_t *p_fifo, char element);int fifo_s_puts(fifo_s_t *p_fifo, char *p_source, int len);int fifo_s_puts_noprotect(fifo_s_t *p_fifo, char *p_source, int len);//******************************************************************************************////! \brief  Get an element from FIFO(in single mode).//!//! \param  [in]  p_fifo is the pointer of valid FIFO.//!//! \retval the data element of FIFO.////******************************************************************************************char fifo_s_get(fifo_s_t *p_fifo);int fifo_s_gets(fifo_s_t *p_fifo, char *p_dest, int len);int fifo_s_gets_noprotect(fifo_s_t *p_fifo, char *p_dest, int len);//******************************************************************************************////! \brief  Pre-Read an element from FIFO(in single mode).//!//! \param  [in]  p_fifo is the pointer of valid FIFO.//! \param  [in]  Offset is the offset from current pointer.//!//! \retval the data element of FIFO.////******************************************************************************************char fifo_s_preread(fifo_s_t *p_fifo, int offset);int fifo_s_prereads(fifo_s_t *p_fifo, char *p_dest, int offset, int len);//******************************************************************************************////! \brief  FIFO is empty (in single mode)?//!//! \param  [in] p_fifo is the pointer of valid FIFO.//!//! \retval - None-zero(true) if empty.//!         - Zero(false) if not empty.////******************************************************************************************char fifo_s_isempty(fifo_s_t *p_fifo);//******************************************************************************************////! \brief  FIFO is full (in single mode)?//!//! \param  [in] p_fifo is the pointer of valid FIFO.//!//! \retval - None-zero(true) if full.//!         - Zero(false) if not full.////******************************************************************************************char fifo_s_isfull(fifo_s_t *p_fifo);//******************************************************************************************////! \brief  Get FIFO the number of elements(in single mode)?//!//! \param  [in] p_fifo is the pointer of valid FIFO.//!//! \retval The number of elements in FIFO.////******************************************************************************************int fifo_s_used(fifo_s_t *p_fifo);//******************************************************************************************////! \brief  Get FIFO the number of elements(in single mode)?//!//! \param  [in] p_fifo is the pointer of valid FIFO.//!//! \retval The number of elements in FIFO.////******************************************************************************************int fifo_s_free(fifo_s_t *p_fifo);//******************************************************************************************////! \brief  Flush the content of FIFO.//!//! \param  [in] p_fifo is the pointer of valid FIFO.//!//! \retval 0 if success, -1 if failure.////******************************************************************************************void fifo_s_flush(fifo_s_t *p_fifo);int fifo_s_discard(fifo_s_t *p_fifo, int len);//******************************************************************************************////! \brief  Create An New FIFO Instance.//! This function allocate enought room for N blocks fifo elements, then return the pointer//! of FIFO.//!//! \param  [in] UnitSize is fifo element size.//! \param  [in] UnitCnt is count of fifo elements.//! \retval The Pointer of FIFO instance, return NULL is failure to allocate memory.//!//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>//!            Header file before use this function.//! \note   -# Functions FIFO_Create and FIFO_Destory must be used in pairs.//!//******************************************************************************************fifo_t *fifo_create(char unit_size, int unit_cnt);//******************************************************************************************////! \brief  Destory FIFO Instance.//!  This function release memory, then reinit the FIFO struct.//!//! \param  [in] pFIFO is the pointer of FIFO instance//! \retval None.//!//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>//!            Header file before use this function.////******************************************************************************************void fifo_destory(fifo_t *p_fifo);//******************************************************************************************////! \brief  Initialize an static FIFO struct.//!//! \param  [in] pFIFO is the pointer of valid FIFO instance.//! \param  [in] pBaseAddr is the base address of pre-allocate memory, such as array.//! \param  [in] UnitSize is fifo element size.//! \param  [in] UnitCnt is count of fifo elements.//! \retval 0 if initialize successfully, otherwise return -1.////******************************************************************************************int fifo_init(fifo_t *p_fifo, void *p_base_addr, char unit_size, int unit_cnt);//******************************************************************************************////! \brief  Put an element into FIFO.//!//! \param  [in]  pFIFO is the pointer of valid FIFO.//! \param  [in]  pElement is the address of element you want to put//!//! \retval 0 if operate successfully, otherwise return -1.////******************************************************************************************int fifo_put(fifo_t *p_fifo, void *p_element);int fifo_put_noprotect(fifo_t *p_fifo, void *p_element);//******************************************************************************************////! \brief  Get an element from FIFO.//!//! \param  [in]  pFIFO is the pointer of valid FIFO.//! \param  [out] pElement is the address of element you want to get//!//! \retval 0 if operate successfully, otherwise return -1.////******************************************************************************************int fifo_get(fifo_t *p_fifo, void *p_element);int fifo_get_noprotect(fifo_t *p_fifo, void *p_element);//******************************************************************************************////! \brief  Pre-Read an element from FIFO.//!//! \param  [in]  pFIFO is the pointer of valid FIFO.//! \param  [in]  Offset is the offset from current pointer.//! \param  [out] pElement is the address of element you want to get//!//! \retval 0 if operate successfully, otherwise return -1.////******************************************************************************************int fifo_pre_read(fifo_t *p_fifo, char offset, void *p_element);//******************************************************************************************////! \brief  FIFO is empty ?//!//! \param  [in] pFIFO is the pointer of valid FIFO.//!//! \retval - None-zero(true) if empty.//!         - Zero(false) if not empty.////******************************************************************************************int fifo_is_empty(fifo_t *p_fifo);//******************************************************************************************////! \brief  FIFO is full ?//!//! \param  [in] pFIFO is the pointer of valid FIFO.//!//! \retval - None-zero(true) if full.//!         - Zero(false) if not full.////******************************************************************************************int fifo_is_full(fifo_t *p_fifo);//******************************************************************************************////! \brief  Get FIFO the number of elements?//!//! \param  [in] pFIFO is the pointer of valid FIFO.//!//! \retval The number of elements in FIFO.////******************************************************************************************int fifo_used(fifo_t *p_fifo);//******************************************************************************************////! \brief  Get FIFO the number of elements?//!//! \param  [in] pFIFO is the pointer of valid FIFO.//!//! \retval The number of elements in FIFO.////******************************************************************************************int fifo_free(fifo_t *p_fifo);//******************************************************************************************////! \brief  Flush the content of FIFO.//!//! \param  [in] pFIFO is the pointer of valid FIFO.//!//! \retval 0 if success, -1 if failure.////******************************************************************************************int fifo_flush(fifo_t *p_fifo);#ifdef __cplusplus
}
#endif#endif // __FIFO_H__

//******************************************************************************************
//!
//! \file   FIFO.c
//! \brief  Genernal FIFO Model Interface.
//!         You can use uniform FIFO Model to manager Any type of data element.
//! \author cedar
//! \changed damom.li
//! \changed sky.huang
//! \date   2016-11-03//! \date   2013-12-16
//! \email  xuesong5825718@gmail.com
//!
//! \version: 1.1 add fifo_s_gets_noprotect function
//!
//! Copyright (c) 2013 Cedar MIT License
//!
//! Permission is hereby granted, free of charge, to any person obtaining a copy
//! of this software and associated documentation files (the "Software"), to deal
//! in the Software without restriction, including without limitation the rights to
//! use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
//! the Software, and to permit persons to whom the Software is furnished to do so,
//! subject to the following conditions:
//!
//! The above copyright notice and this permission notice shall be included in all
//! copies or substantial portions of the Software.
//!
//! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//! IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//! FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//! AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//! LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//! OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
//! IN THE SOFTWARE.
///
//******************************************************************************************
#include "fifo.h"//******************************************************************************************
//!                     ASSERT MACRO
//******************************************************************************************
#ifndef ASSERT#ifdef FIFO_NDEBUG
#define ASSERT(x)
#else
#define ASSERT(x)                                           \do                                                      \{                                                       \if (!(x))                                           \printf("[assert]: %s, %d", __FILE__, __LINE__); \while (!(x))                                        \;                                               \} while (0)
#endif#endif // ASSERT#ifdef USE_DYNAMIC_MEMORY
//******************************************************************************************
//
//! \brief  Create An New FIFO Instance(in Single Mode).
//! This function allocate enought room for N blocks fifo elements, then return the pointer
//! of FIFO.
//!
//! \param  [in] uint_cnt is count of fifo elements.
//! \retval The Pointer of FIFO instance, return NULL is failure to allocate memory.
//!
//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>
//!            Header file before use this function.
//! \note   -# Functions FIFO_Create and FIFO_Destory must be used in pairs.
//!
//******************************************************************************************
fifo_s_t *fifo_s_create(int uint_cnt)
{fifo_s_t *p_fifo = NULL;  //!< FIFO Pointerchar *p_base_addr = NULL; //!< Memory Base Address//! Check input parameters.ASSERT(uint_cnt);//! Allocate Memory for pointer of new FIFO Control Blockp_fifo = (fifo_s_t *)malloc(sizeof(fifo_s_t));if (NULL == p_fifo){//! Allocate Failure, exit nowreturn (NULL);}//! Allocate Memory for pointer of new FIFOp_base_addr = malloc(uint_cnt);if (NULL == p_base_addr){//! Allocate Failure, exit nowfree(p_fifo);return (NULL);}//! Initialize General FIFO Modulefifo_s_init(p_fifo, p_base_addr, uint_cnt);return (p_fifo);
}//******************************************************************************************
//
//! \brief  Destory FIFO Instance(in Single Mode).
//!  This function release memory, then reinit the FIFO struct.
//!
//! \param  [in] p_fifo is the pointer of FIFO instance
//! \retval None.
//!
//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>
//!            Header file before use this function.
//
//******************************************************************************************
void fifo_s_destroy(fifo_s_t *p_fifo)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_fifo->p_start_addr);//! Free FIFO memoryfree(p_fifo->p_start_addr);//! Free FIFO Control Block memoryfree(p_fifo);return; //!< Success
}#endif // USE_DYNAMIC_MEMORY//******************************************************************************************
//
//! \brief  Initialize an static FIFO struct(in single mode).
//!
//! \param  [in] p_fifo is the pointer of valid FIFO instance.
//! \param  [in] p_base_addr is the base address of pre-allocate memory, such as array.
//! \param  [in] uint_cnt is count of fifo elements.
//! \retval 0 if initialize successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_s_init(fifo_s_t *p_fifo, void *p_base_addr, int uint_cnt)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_base_addr);ASSERT(uint_cnt);//! Initialize FIFO Control Block.p_fifo->p_start_addr = (char *)p_base_addr;p_fifo->p_end_addr = (char *)p_base_addr + uint_cnt - 1;p_fifo->free_num = uint_cnt;p_fifo->used_num = 0;p_fifo->p_read_addr = (char *)p_base_addr;p_fifo->p_write_addr = (char *)p_base_addr;//! Inint mutex for new FIFOMUTEX_INIT(p_fifo->mutex);return (0);
}//******************************************************************************************
//
//! \brief  Put an element into FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//! \param  [in]  element is the data element you want to put
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_s_put(fifo_s_t *p_fifo, char element)
{//! Check input parameters.ASSERT(p_fifo);if (0 == p_fifo->free_num){//! Error, FIFO is full!return (-1);}MUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->free_num){//! Error, FIFO is full!MUTEX_UNLOCK(p_fifo->mutex);return (-1);}if (p_fifo->p_write_addr > p_fifo->p_end_addr){p_fifo->p_write_addr = p_fifo->p_start_addr;}*(p_fifo->p_write_addr) = element;p_fifo->p_write_addr++;p_fifo->free_num--;p_fifo->used_num++;MUTEX_UNLOCK(p_fifo->mutex);return (0);
}//******************************************************************************************
//
//! \brief  Put some elements into FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//! \param  [in]  p_source is the data element you want to put
//! \param  [in]  the number of elements
//! \retval the number of really write data, otherwise return -1.
//
//******************************************************************************************
int fifo_s_puts(fifo_s_t *p_fifo, char *p_source, int len)
{int retval;int len_to_end;int len_from_start;ASSERT(p_fifo);if (NULL == p_source){return -1;}if (0 == p_fifo->free_num){return 0;}MUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->free_num){MUTEX_UNLOCK(p_fifo->mutex);return 0;}if (p_fifo->p_write_addr > p_fifo->p_end_addr){p_fifo->p_write_addr = p_fifo->p_start_addr;}len = (len < p_fifo->free_num) ? len : p_fifo->free_num;len_to_end = p_fifo->p_end_addr - p_fifo->p_write_addr + 1;if (len_to_end >= len) //no rollback{len_to_end = len;memcpy(p_fifo->p_write_addr, p_source, len_to_end);p_fifo->p_write_addr += len_to_end;}else //rollback{len_from_start = len - len_to_end;memcpy(p_fifo->p_write_addr, p_source, len_to_end);memcpy(p_fifo->p_start_addr, p_source + len_to_end, len_from_start);p_fifo->p_write_addr = p_fifo->p_start_addr + len_from_start;}p_fifo->free_num -= len;p_fifo->used_num += len;retval = len;MUTEX_UNLOCK(p_fifo->mutex);return retval;
}//******************************************************************************************
//
//! \brief  Put some elements into FIFO, ingnore the interrupt
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//! \param  [in]  p_source is the data element you want to put
//! \param  [in]  the number of elements
//! \retval the number of really write data, otherwise return -1.
//
//******************************************************************************************
int fifo_s_puts_noprotect(fifo_s_t *p_fifo, char *p_source, int len)
{int retval;int len_to_end;int len_from_start;ASSERT(p_fifo);if (NULL == p_source){return -1;}if (0 == p_fifo->free_num){return 0;}if (p_fifo->p_write_addr > p_fifo->p_end_addr){p_fifo->p_write_addr = p_fifo->p_start_addr;}len = (len < p_fifo->free_num) ? len : p_fifo->free_num;len_to_end = p_fifo->p_end_addr - p_fifo->p_write_addr + 1;if (len_to_end >= len) //no rollback{len_to_end = len;memcpy(p_fifo->p_write_addr, p_source, len_to_end);p_fifo->p_write_addr += len_to_end;}else //rollback{len_from_start = len - len_to_end;memcpy(p_fifo->p_write_addr, p_source, len_to_end);memcpy(p_fifo->p_start_addr, p_source + len_to_end, len_from_start);p_fifo->p_write_addr = p_fifo->p_start_addr + len_from_start;}p_fifo->free_num -= len;p_fifo->used_num += len;retval = len;return retval;
}//******************************************************************************************
//
//! \brief  Get an element from FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//!
//! \retval the data element of FIFO.
//
//******************************************************************************************
char fifo_s_get(fifo_s_t *p_fifo)
{char retval = 0;//! Check input parameters.ASSERT(p_fifo);//TODO:if (0 == p_fifo->used_num){return 0;}MUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->used_num){MUTEX_UNLOCK(p_fifo->mutex);return 0;}if (p_fifo->p_read_addr > p_fifo->p_end_addr){p_fifo->p_read_addr = p_fifo->p_start_addr;}retval = *p_fifo->p_read_addr;// Update informationp_fifo->p_read_addr++;p_fifo->free_num++;p_fifo->used_num--;MUTEX_UNLOCK(p_fifo->mutex);return (retval);
}//******************************************************************************************
//
//! \brief  Get some element from FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//!
//! \retval the number of really read data.
//
//******************************************************************************************
int fifo_s_gets(fifo_s_t *p_fifo, char *p_dest, int len)
{int retval;int len_to_end;int len_from_start;ASSERT(p_fifo);if (NULL == p_dest){return -1;}if (0 == p_fifo->used_num){return 0;}MUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->used_num){MUTEX_UNLOCK(p_fifo->mutex);return 0;}if (p_fifo->p_read_addr > p_fifo->p_end_addr){p_fifo->p_read_addr = p_fifo->p_start_addr;}len = (len < p_fifo->used_num) ? len : p_fifo->used_num;len_to_end = p_fifo->p_end_addr - p_fifo->p_read_addr + 1;if (len_to_end >= len) //no rollback{len_to_end = len;memcpy(p_dest, p_fifo->p_read_addr, len_to_end);p_fifo->p_read_addr += len_to_end;}else //rollback{len_from_start = len - len_to_end;memcpy(p_dest, p_fifo->p_read_addr, len_to_end);memcpy(p_dest + len_to_end, p_fifo->p_start_addr, len_from_start);p_fifo->p_read_addr = p_fifo->p_start_addr + len_from_start;}p_fifo->free_num += len;p_fifo->used_num -= len;retval = len;MUTEX_UNLOCK(p_fifo->mutex);return retval;
}//******************************************************************************************
//
//! \brief  Get some element from FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//!
//! \retval the number of really read data.
//
//******************************************************************************************
int fifo_s_gets_noprotect(fifo_s_t *p_fifo, char *p_dest, int len)
{int retval;int len_to_end;int len_from_start;ASSERT(p_fifo);if (NULL == p_dest){return -1;}if (0 == p_fifo->used_num){return 0;}if (p_fifo->p_read_addr > p_fifo->p_end_addr){p_fifo->p_read_addr = p_fifo->p_start_addr;}len = (len < p_fifo->used_num) ? len : p_fifo->used_num;len_to_end = p_fifo->p_end_addr - p_fifo->p_read_addr + 1;if (len_to_end >= len) //no rollback{len_to_end = len;memcpy(p_dest, p_fifo->p_read_addr, len_to_end);p_fifo->p_read_addr += len_to_end;}else //rollback{len_from_start = len - len_to_end;memcpy(p_dest, p_fifo->p_read_addr, len_to_end);memcpy(p_dest + len_to_end, p_fifo->p_start_addr, len_from_start);p_fifo->p_read_addr = p_fifo->p_start_addr + len_from_start;}p_fifo->free_num += len;p_fifo->used_num -= len;retval = len;return retval;
}//******************************************************************************************
//
//! \brief  Pre-Read an element from FIFO(in single mode).
//!
//! \param  [in]  p_fifo is the pointer of valid FIFO.
//! \param  [in]  Offset is the offset from current pointer.
//!
//! \retval the data element of FIFO.
//
//******************************************************************************************
char fifo_s_preread(fifo_s_t *p_fifo, int offset)
{char *tmp_read_addr;//! Check input parameters.ASSERT(p_fifo);if (offset > p_fifo->used_num){return 0;}else{// Move Read Pointer to right positiontmp_read_addr = p_fifo->p_read_addr + offset;if (tmp_read_addr > p_fifo->p_end_addr){tmp_read_addr = tmp_read_addr - p_fifo->p_end_addr + p_fifo->p_start_addr - 1;}return *tmp_read_addr;}
}/******/
int fifo_s_prereads(fifo_s_t *p_fifo, char *p_dest, int offset, int len)
{int retval;char *tmp_read_addr;int len_to_end;int len_from_start;ASSERT(p_fifo);if (NULL == p_dest){return -1;}if (0 == p_fifo->used_num){return -1;}if (offset >= p_fifo->used_num){return -1;}MUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->used_num){MUTEX_UNLOCK(p_fifo->mutex);return -1;}if (offset >= p_fifo->used_num){MUTEX_UNLOCK(p_fifo->mutex);return -1;}tmp_read_addr = p_fifo->p_read_addr + offset;if (tmp_read_addr > p_fifo->p_end_addr){tmp_read_addr = tmp_read_addr - p_fifo->p_end_addr + p_fifo->p_start_addr - 1;}len = (len < (p_fifo->used_num - offset)) ? len : (p_fifo->used_num - offset);len_to_end = p_fifo->p_end_addr - tmp_read_addr + 1;if (len_to_end >= len) //no rollback{len_to_end = len;memcpy(p_dest, tmp_read_addr, len_to_end);}else //rollback{len_from_start = len - len_to_end;memcpy(p_dest, tmp_read_addr, len_to_end);memcpy(p_dest + len_to_end, p_fifo->p_start_addr, len_from_start);}retval = len;MUTEX_UNLOCK(p_fifo->mutex);return retval;
}//******************************************************************************************
//
//! \brief  FIFO is empty (in single mode)?
//!
//! \param  [in] p_fifo is the pointer of valid FIFO.
//!
//! \retval - None-zero(true) if empty.
//!         - Zero(false) if not empty.
//
//******************************************************************************************
char fifo_s_isempty(fifo_s_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (p_fifo->used_num ? 0 : 1);
}//******************************************************************************************
//
//! \brief  FIFO is full (in single mode)?
//!
//! \param  [in] p_fifo is the pointer of valid FIFO.
//!
//! \retval - None-zero(true) if full.
//!         - Zero(false) if not full.
//
//******************************************************************************************
char fifo_s_isfull(fifo_s_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (p_fifo->free_num ? 0 : 1);
}//******************************************************************************************
//
//! \brief  Get FIFO the number of elements(in single mode)?
//!
//! \param  [in] p_fifo is the pointer of valid FIFO.
//!
//! \retval The number of elements in FIFO.
//
//******************************************************************************************
int fifo_s_used(fifo_s_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return p_fifo->used_num;
}//******************************************************************************************
//
//! \brief  Get FIFO the number of elements(in single mode)?
//!
//! \param  [in] p_fifo is the pointer of valid FIFO.
//!
//! \retval The number of elements in FIFO.
//
//******************************************************************************************
int fifo_s_free(fifo_s_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return p_fifo->free_num;
}//******************************************************************************************
//
//! \brief  Flush the content of FIFO.
//!
//! \param  [in] p_fifo is the pointer of valid FIFO.
//!
//! \retval 0 if success, -1 if failure.
//
//******************************************************************************************
void fifo_s_flush(fifo_s_t *p_fifo)
{//! Check input parameters.ASSERT(p_fifo);//! Initialize FIFO Control Block.MUTEX_LOCK(p_fifo->mutex);p_fifo->free_num = p_fifo->p_end_addr - p_fifo->p_start_addr + 1;p_fifo->used_num = 0;p_fifo->p_read_addr = p_fifo->p_start_addr;p_fifo->p_write_addr = p_fifo->p_start_addr;MUTEX_UNLOCK(p_fifo->mutex);
}int fifo_s_discard(fifo_s_t *p_fifo, int len)
{//! Check input parameters.char *tmp_index;ASSERT(p_fifo);MUTEX_LOCK(p_fifo->mutex);if (len > p_fifo->used_num){len = p_fifo->used_num;}tmp_index = len + p_fifo->p_read_addr;if (tmp_index > p_fifo->p_end_addr){tmp_index = tmp_index - p_fifo->p_end_addr + p_fifo->p_start_addr - 1;}p_fifo->p_read_addr = tmp_index;p_fifo->free_num += len;p_fifo->used_num -= len;MUTEX_UNLOCK(p_fifo->mutex);return len;
}#ifdef USE_DYNAMIC_MEMORY
//******************************************************************************************
//
//! \brief  Create An New FIFO Instance.
//! This function allocate enought room for N blocks fifo elements, then return the pointer
//! of FIFO.
//!
//! \param  [in] UnitSize is fifo element size.
//! \param  [in] UnitCnt is count of fifo elements.
//! \retval The Pointer of FIFO instance, return NULL is failure to allocate memory.
//!
//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>
//!            Header file before use this function.
//! \note   -# Functions FIFO_Create and FIFO_Destory must be used in pairs.
//!
//******************************************************************************************
fifo_t *fifo_create(char unit_size, int unit_cnt)
{fifo_t *p_fifo = NULL;    //!< FIFO Pointerchar *p_base_addr = NULL; //!< Memory Base Address//! Check input parameters.ASSERT(unit_size);ASSERT(unit_cnt);//! Allocate Memory for pointer of new FIFO Control Block.p_fifo = (fifo_t *)malloc(sizeof(fifo_t));if (NULL == p_fifo){//! Allocate Failure, exit now.return (NULL);}//! Allocate memory for FIFO.p_base_addr = malloc(unit_size * unit_cnt);if (NULL == p_base_addr){//! Allocate Failure, exit now.free(p_fifo);return (NULL);}//! Initialize General FIFO Module.fifo_init(p_fifo, p_base_addr, unit_size, unit_cnt);return (p_fifo);
}//******************************************************************************************
//
//! \brief  Destory FIFO Instance.
//!  This function release memory, then reinit the FIFO struct.
//!
//! \param  [in] pFIFO is the pointer of FIFO instance
//! \retval None.
//!
//! \note   -# You must enable USE_MEMORY_ALLOC macro and ensure your system have <stdlib.h>
//!            Header file before use this function.
//
//******************************************************************************************
void fifo_destory(fifo_t *p_fifo)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_fifo->p_start_addr);//! Free FIFO memoryfree(p_fifo->p_start_addr);//! Free FIFO Control Block memory.free(p_fifo);return; //!< Success
}#endif // USE_DYNAMIC_MEMORY//******************************************************************************************
//
//! \brief  Initialize an static FIFO struct.
//!
//! \param  [in] pFIFO is the pointer of valid FIFO instance.
//! \param  [in] pBaseAddr is the base address of pre-allocate memory, such as array.
//! \param  [in] UnitSize is fifo element size.
//! \param  [in] UnitCnt is count of fifo elements.
//! \retval 0 if initialize successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_init(fifo_t *p_fifo, void *p_base_addr, char unit_size, int unit_cnt)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_base_addr);ASSERT(unit_size);ASSERT(unit_cnt);//! Initialize FIFO Control Block.p_fifo->p_start_addr = (char *)p_base_addr;p_fifo->p_end_addr = (char *)p_base_addr + unit_size * unit_cnt - 1;p_fifo->free_num = unit_cnt;p_fifo->used_num = 0;p_fifo->unit_size = unit_size;p_fifo->p_read_addr = (char *)p_base_addr;p_fifo->p_write_addr = (char *)p_base_addr;MUTEX_INIT(p_fifo->mutex);return (0);
}//******************************************************************************************
//
//! \brief  Put an element into FIFO.
//!
//! \param  [in]  pFIFO is the pointer of valid FIFO.
//! \param  [in]  pElement is the address of element you want to put
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_put(fifo_t *p_fifo, void *p_element)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_element);// Full ?if (0 == p_fifo->free_num){//! Error, FIFO is full!return (-1);}//! Copy DataMUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->free_num){//! Error, FIFO is full!MUTEX_UNLOCK(p_fifo->mutex);return (-1);}if (p_fifo->p_write_addr > p_fifo->p_end_addr){p_fifo->p_write_addr = p_fifo->p_start_addr;}memcpy(p_fifo->p_write_addr, p_element, p_fifo->unit_size);p_fifo->p_write_addr += p_fifo->unit_size;p_fifo->free_num--;p_fifo->used_num++;MUTEX_UNLOCK(p_fifo->mutex);return (0);
}//******************************************************************************************
//
//! \brief  Put an element into FIFO without protect.
//!
//! \param  [in]  pFIFO is the pointer of valid FIFO.
//! \param  [in]  pElement is the address of element you want to put
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_put_noprotect(fifo_t *p_fifo, void *p_element)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_element);// Full ?if (0 == p_fifo->free_num){//! Error, FIFO is full!return (-1);}if (p_fifo->p_write_addr > p_fifo->p_end_addr){p_fifo->p_write_addr = p_fifo->p_start_addr;}memcpy(p_fifo->p_write_addr, p_element, p_fifo->unit_size);p_fifo->p_write_addr += p_fifo->unit_size;p_fifo->free_num--;p_fifo->used_num++;return (0);
}//******************************************************************************************
//
//! \brief  Get an element from FIFO without protect.
//!
//! \param  [in]  pFIFO is the pointer of valid FIFO.
//! \param  [out] pElement is the address of element you want to get
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_get(fifo_t *p_fifo, void *p_element)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_element);// Empty ?if (0 == p_fifo->used_num){//! Error, FIFO is Empty!return (-1);}//! Copy DataMUTEX_LOCK(p_fifo->mutex);if (0 == p_fifo->used_num){//! Error, FIFO is Empty!MUTEX_UNLOCK(p_fifo->mutex);return (-1);}if (p_fifo->p_read_addr > p_fifo->p_end_addr){p_fifo->p_read_addr = p_fifo->p_start_addr;}memcpy(p_element, p_fifo->p_read_addr, p_fifo->unit_size);p_fifo->p_read_addr += p_fifo->unit_size;p_fifo->free_num++;p_fifo->used_num--;MUTEX_UNLOCK(p_fifo->mutex);return (0);
}//******************************************************************************************
//
//! \brief  Get an element from FIFO.
//!
//! \param  [in]  pFIFO is the pointer of valid FIFO.
//! \param  [out] pElement is the address of element you want to get
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_get_noprotect(fifo_t *p_fifo, void *p_element)
{//! Check input parameters.ASSERT(p_fifo);ASSERT(p_element);// Empty ?if (0 == p_fifo->used_num){//! Error, FIFO is Empty!return (-1);}if (p_fifo->p_read_addr > p_fifo->p_end_addr){p_fifo->p_read_addr = p_fifo->p_start_addr;}memcpy(p_element, p_fifo->p_read_addr, p_fifo->unit_size);p_fifo->p_read_addr += p_fifo->unit_size;p_fifo->free_num++;p_fifo->used_num--;return (0);
}//******************************************************************************************
//
//! \brief  Pre-Read an element from FIFO.
//!
//! \param  [in]  pFIFO is the pointer of valid FIFO.
//! \param  [in]  Offset is the offset from current pointer.
//! \param  [out] pElement is the address of element you want to get
//!
//! \retval 0 if operate successfully, otherwise return -1.
//
//******************************************************************************************
int fifo_pre_read(fifo_t *p_fifo, char offset, void *p_element)
{char *_pre_red_index = (void *)0;//! Check input parameters.ASSERT(p_fifo);ASSERT(p_element);// OverFlow ?if (offset >= p_fifo->used_num){return (-1);}// Move Read Pointer to right position_pre_red_index = p_fifo->p_read_addr + p_fifo->unit_size * offset;while (_pre_red_index > p_fifo->p_end_addr){_pre_red_index = _pre_red_index - p_fifo->p_end_addr + p_fifo->p_start_addr - 1;}//! Copy Datamemcpy(p_element, _pre_red_index, p_fifo->unit_size);return (0);
}//******************************************************************************************
//
//! \brief  FIFO is empty ?
//!
//! \param  [in] pFIFO is the pointer of valid FIFO.
//!
//! \retval - None-zero(true) if empty.
//!         - Zero(false) if not empty.
//
//******************************************************************************************
int fifo_is_empty(fifo_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (0 == p_fifo->used_num);
}//******************************************************************************************
//
//! \brief  FIFO is full ?
//!
//! \param  [in] pFIFO is the pointer of valid FIFO.
//!
//! \retval - None-zero(true) if full.
//!         - Zero(false) if not full.
//
//******************************************************************************************
int fifo_is_full(fifo_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (0 == p_fifo->free_num);
}//******************************************************************************************
//
//! \brief  Get FIFO the number of elements?
//!
//! \param  [in] pFIFO is the pointer of valid FIFO.
//!
//! \retval The number of elements in FIFO.
//
//******************************************************************************************
int fifo_used(fifo_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (p_fifo->used_num);
}//******************************************************************************************
//
//! \brief  Get FIFO the number of elements?
//!
//! \param  [in] pFIFO is the pointer of valid FIFO.
//!
//! \retval The number of elements in FIFO.
//
//******************************************************************************************
int fifo_free(fifo_t *p_fifo)
{//! Check input parameter.ASSERT(p_fifo);return (p_fifo->free_num);
}//******************************************************************************************
//
//! \brief  Flush the content of FIFO.
//!
//! \param  [in] pFIFO is the pointer of valid FIFO.
//!
//! \retval 0 if success, -1 if failure.
//
//******************************************************************************************
int fifo_flush(fifo_t *p_fifo)
{//! Check input parameters.ASSERT(p_fifo);//! Initialize FIFO Control Block.MUTEX_LOCK(p_fifo->mutex);p_fifo->free_num = (p_fifo->p_end_addr - p_fifo->p_start_addr) / (p_fifo->unit_size);p_fifo->used_num = 0;p_fifo->p_read_addr = p_fifo->p_start_addr;p_fifo->p_write_addr = p_fifo->p_start_addr;MUTEX_UNLOCK(p_fifo->mutex);return (0);
}

2.7 重定向printf到串口打印

#ifdef __GNUC__
/* With GCC, small printf (option LD Linker->Libraries->Small printfset to 'Yes') calls __io_putchar() */
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */PUTCHAR_PROTOTYPE
{/* Place your implementation of fputc here *//* e.g. write a character to the EVAL_COM1 and Loop until the end of transmission */HAL_UART_Transmit(&huart2, (uint8_t *)&ch, 1, 0xFFFF);return ch;
}

2.8 结合fifo和i2s dma读取i2s音频数据并通过usb虚拟串口转发上位机

 HAL_Delay(1000);printf("dma size:%lu\n", sizeof(dma));g_i2s_dma_recv_fifo = fifo_s_create(480);if (!g_i2s_dma_recv_fifo) {printf("fifo cre failed.\n");return -1;}HAL_I2S_Receive_DMA(&hi2s2, (uint16_t *)dma, 2);while (1){/* USER CODE END WHILE *//* USER CODE BEGIN 3 */if (!fifo_s_isempty(g_i2s_dma_recv_fifo)) {char res[4] = {'\0'};if (fifo_s_gets(g_i2s_dma_recv_fifo, res, sizeof(res)) > 0) {CDC_Transmit_HS((uint8_t*)res, sizeof(res));}}}fifo_s_destroy(g_i2s_dma_recv_fifo);

uint16_t dma[2] = {'\0'};
fifo_s_t *g_i2s_dma_recv_fifo = NULL;void HAL_I2S_RxCpltCallback(I2S_HandleTypeDef *hi2s)
{if(hi2s==&hi2s2) {if (dma[0] || dma[1]) {if (!fifo_s_isfull(g_i2s_dma_recv_fifo)) {fifo_s_puts(g_i2s_dma_recv_fifo, (char*)dma, sizeof(dma)/2);}}}
}

2.9 usb虚拟串口接收上位机的pcm数据并通过i2s dma写入音频卡播放

static int8_t CDC_Receive_HS(uint8_t* Buf, uint32_t *Len)
{/* USER CODE BEGIN 11 */uint16_t len = *Len;
//    printf("recv len:%d\n", len);
//    printf("recv:%s\n", Buf);if (!fifo_s_isfull(g_i2s_dma_send_fifo)) {fifo_s_puts(g_i2s_dma_send_fifo, (char*)Buf, *Len);} else {printf("fifo is full!\n");}USBD_CDC_SetRxBuffer(&hUsbDeviceHS, &Buf[0]);USBD_CDC_ReceivePacket(&hUsbDeviceHS);return (USBD_OK);/* USER CODE END 11 */
}

2.10 融合收发DMA（只有一个方向可以生效，收发需要配置不通模式，无法实现全双工收发，而且需要配置SPI全局中断）

fifo_s_t *g_i2s_dma_send_fifo = NULL;uint16_t dma[2] = {'\0'};
fifo_s_t *g_i2s_dma_recv_fifo = NULL;void HAL_I2S_RxCpltCallback(I2S_HandleTypeDef *hi2s)
{if(hi2s==&hi2s2) {if (dma[0] || dma[1]) {if (!fifo_s_isfull(g_i2s_dma_recv_fifo)) {fifo_s_puts(g_i2s_dma_recv_fifo, (char*)dma, sizeof(dma)/2);}}}
}

HAL_Delay(1000);printf("dma size:%lu\n", sizeof(dma));g_i2s_dma_send_fifo = fifo_s_create(4 * 4800);if (!g_i2s_dma_send_fifo) {printf("fifo cre failed.\n");return -1;}g_i2s_dma_recv_fifo = fifo_s_create(480);if (!g_i2s_dma_recv_fifo) {printf("fifo cre failed.\n");return -1;}HAL_I2S_Receive_DMA(&hi2s2, (uint16_t *)dma, 2);while (1){/* USER CODE END WHILE *//* USER CODE BEGIN 3 */if (!fifo_s_isempty(g_i2s_dma_recv_fifo)) {char res[4] = {'\0'};if (fifo_s_gets(g_i2s_dma_recv_fifo, res, sizeof(res)) > 0) {CDC_Transmit_HS((uint8_t*)res, sizeof(res));}}if (!fifo_s_isempty(g_i2s_dma_send_fifo)) {char res[4 * 48] = {'\0'};if (fifo_s_gets(g_i2s_dma_send_fifo, res, sizeof(res)) > 0) {printf("res:%02x%02x\n", res[0], res[1]);while (HAL_I2S_GetState(&hi2s2) != HAL_I2S_STATE_READY) {}int ret = HAL_I2S_Transmit_DMA(&hi2s2,(uint16_t*)res, sizeof(res));
//                int ret = HAL_I2SEx_TransmitReceive_DMA(&hi2s2,(uint16_t*)res, dma, 48);
//                int ret = HAL_I2S_Transmit(&hi2s2,(uint16_t*)res, 48, 0xFFFF);if (ret != HAL_OK) {printf("ret:%d\n", ret);while (HAL_I2S_GetState(&hi2s2) != HAL_I2S_STATE_READY) {}}}}}fifo_s_destroy(g_i2s_dma_recv_fifo);fifo_s_destroy(g_i2s_dma_send_fifo);

2.11 全双工收发进行录音和放音（最终版本结合DMA收和发）

官方给到的例子也是全双工方式进行读写的，注意回调接口别搞错了（https://community.st.com/t5/stm32-mcus-products/stm32f411-hal-driver-i2s-full-duplex-ext-sd-issue/td-p/442735 社区这里提问的人就是搞错了回调接口）：

fifo_s_t *g_i2s_dma_send_fifo = NULL;
uint8_t dma[2 * 2] = {'\0'};
uint8_t send_dma[2 * 2] = {'\0'};
fifo_s_t *g_i2s_dma_recv_fifo = NULL;
uint8_t is_record = 1;
uint8_t is_player = 0;
typedef enum {RECORD_START,RECORD_STOP,PLAYER_START,PLAYER_STOP,
} I2S_STATE;void HAL_I2SEx_TxRxCpltCallback(I2S_HandleTypeDef *hi2s)
{if(hi2s==&hi2s2) {if (is_record) {if (dma[0]) {if (!fifo_s_isfull(g_i2s_dma_recv_fifo)) {fifo_s_puts(g_i2s_dma_recv_fifo, (char *) dma, sizeof(dma));}}}if (is_player) {if (!fifo_s_isempty(g_i2s_dma_send_fifo) && is_player) {char res[4] = {'\0'};if (fifo_s_gets(g_i2s_dma_send_fifo, res, sizeof(res)) > 0) {
//                    printf("i am here.\n");memcpy(send_dma, res, sizeof(res));}}}}
}

	HAL_Delay(1000);printf("dma size:%lu\n", sizeof(dma));g_i2s_dma_send_fifo = fifo_s_create(4 * 4800);if (!g_i2s_dma_send_fifo) {printf("fifo cre failed.\n");return -1;}g_i2s_dma_recv_fifo = fifo_s_create(480);if (!g_i2s_dma_recv_fifo) {printf("fifo cre failed.\n");return -1;}
//    HAL_I2SEx_TransmitReceive(&hi2s2, send_dma, dma, 2, 1000);HAL_I2SEx_TransmitReceive_DMA(&hi2s2, (uint16_t*)send_dma, (uint16_t*)dma, (sizeof(dma)/2));while (1){/* USER CODE END WHILE *//* USER CODE BEGIN 3 */if (!fifo_s_isempty(g_i2s_dma_recv_fifo)) {char res[4] = {'\0'};if (fifo_s_gets(g_i2s_dma_recv_fifo, res, sizeof(res)) > 0) {CDC_Transmit_HS((uint8_t*)res, sizeof(res));}}}fifo_s_destroy(g_i2s_dma_recv_fifo);fifo_s_destroy(g_i2s_dma_send_fifo);

2.12 其它方式

还有一种方式创建较大的缓存区，增加HAL_I2SEx_TxRxHalfCpltCallback回调在接收到一半时处理缓存的前半部分，HAL_I2SEx_TxRxCpltCallback回调处理后半部分缓存。以上都是基于HAL库，还有不基于HAL库的方式，但是不建议使用，HAL库更容易移植一些。

3、难点

3.1 录音

主要是调整i2s dma对应的配置以及将读取到的数据转发给上位机保证不丢采样内容，这个调整尝试过程属于摸着石头过河，很不好调试。比如我这里接收时i2s每次接收两个字节，但是通过usb虚拟串口转发上位机时每次需要发送4个字节，如果每次只发送2个字节则采样数据会丢失一半左右，中间还需要增加fifo缓存解决接收和发送速度不对等的问题。

3.2 放音

测试方式比较麻烦，最好有外接的放音设备，部分音频控制板可以配置自身扬声器显示自身麦克风声音，这样I2S的收发都可以通过一个音频控制卡听到了（但测试录音时记得关闭麦克风）：

3.3 缓存问题

i2s dma收发和存储读写时的速度不对等问题，比如录音时需要从i2s dma读取然后存储到外挂U盘或者flash或者直接串口转发，这时dma读取和存储就有不对等的问题，可能导致采样数据丢失，因此需要中间缓存保证采样数据不丢失，也可以降低采样率；放音时一般一次读取的内容太多导致一次性发送dma时超过缓存大小，因此也最好增加缓存一次性发送一部分内容到dma。
此外，对应i2s的spi全局中断要开启，否则可能出现状态busy的问题：

3.4 底噪问题

发送时进行简单数据过滤，单声道的过滤另一声道的杂音，即不发送部分采样值，以及清空缓存时注意结合半缓存接收回调处理。

如果声音有了，但是有杂音可以录制一下空音看是否有杂音，如果空音有杂音，可以量一下声卡和单片机的主频，可能作为从模式的一方主频并未禁用，导致连接主频mclk后有干扰导致的杂音。
除了硬件问题外，软件读写文件也需要注意，这也容易引起底噪，比如录音时flash的擦除影响写文件，放音时读取文件往dma填充时读取文件的大小和填充0不正常导致放音底噪，这里一定记得参考一下官网的audio示例（回调中获取过半和完全传输完成的标志后再填充，之后还原标志）：

void WavePlayBack(uint32_t AudioFreq)
{ UINT bytesread = 0;/* Start playing */AudioPlayStart = 1;RepeatState = REPEAT_ON;/* Initialize Wave player (Codec, DMA, I2C) */if(WavePlayerInit(AudioFreq) != 0){Error_Handler();}/* Get Data from USB Flash Disk */f_lseek(&FileRead, 0);f_read (&FileRead, &Audio_Buffer[0], AUDIO_BUFFER_SIZE, &bytesread);AudioRemSize = WaveDataLength - bytesread;/* Start playing Wave */BSP_AUDIO_OUT_Play((uint16_t*)&Audio_Buffer[0], AUDIO_BUFFER_SIZE);LEDsState = LED6_TOGGLE;PauseResumeStatus = RESUME_STATUS;PressCount = 0;/* Check if the device is connected.*/while((AudioRemSize != 0) && (AppliState != APPLICATION_IDLE)){ /* Test on the command: Playing */if(CmdIndex == CMD_PLAY){ if(PauseResumeStatus == PAUSE_STATUS){/* Stop Toggling LED2 to signal Pause */LEDsState = STOP_TOGGLE;/* Pause playing Wave */WavePlayerPauseResume(PauseResumeStatus);PauseResumeStatus = IDLE_STATUS;}else if(PauseResumeStatus == RESUME_STATUS){/* Toggling LED6 to signal Play */LEDsState = LED6_TOGGLE;/* Resume playing Wave */WavePlayerPauseResume(PauseResumeStatus);PauseResumeStatus = IDLE_STATUS;}  bytesread = 0;if(BufferOffset == BUFFER_OFFSET_HALF){f_read(&FileRead, &Audio_Buffer[0], AUDIO_BUFFER_SIZE/2, (void *)&bytesread); BufferOffset = BUFFER_OFFSET_NONE;}if(BufferOffset == BUFFER_OFFSET_FULL){f_read(&FileRead, &Audio_Buffer[AUDIO_BUFFER_SIZE/2], AUDIO_BUFFER_SIZE/2, (void *)&bytesread); BufferOffset = BUFFER_OFFSET_NONE;} if(AudioRemSize > (AUDIO_BUFFER_SIZE / 2)){AudioRemSize -= bytesread;}else{AudioRemSize = 0;}}else {/* Stop playing Wave */WavePlayerStop();f_close(&FileRead);AudioRemSize = 0;RepeatState = REPEAT_ON;break;}}
#ifdef PLAY_REPEAT_DISABLED RepeatState = REPEAT_OFF;/* Stop playing Wave */WavePlayerStop();f_close(&FileRead);/* Test on the command: Playing */if(CmdIndex == CMD_PLAY){LEDsState = LED4_TOGGLE;}
#else LEDsState = LEDS_OFF;RepeatState = REPEAT_ON;AudioPlayStart = 0;/* Stop playing Wave */WavePlayerStop();f_close(&FileRead);
#endif /* PLAY_REPEAT_DISABLED */
}

3.5 音质问题

目前音频播放有丢低音的情况，播放的音频比较尖锐，缺少低沉浑厚的声音，感觉感觉是单片机的问题。
主要还是配置参数的问题，保证晶振频率设置正确，以及PLLI2SN和PLLI2SR设置好，这个可以通过stm32CubeMX配置后设置。

//采样率计算公式:Fs=I2SxCLK/[256*(2*I2SDIV+ODD)]
//I2SxCLK=(HSE/pllm)*PLLI2SN/PLLI2SR
//一般HSE=8Mhz 
//pllm:在Sys_Clock_Set设置的时候确定，一般是8
//PLLI2SN:一般是192~432 
//PLLI2SR:2~7
//I2SDIV:2~255
//ODD:0/1
//I2S分频系数表@pllm=8,HSE=8Mhz,即vco输入频率为1Mhz
//表格式:采样率/10,PLLI2SN,PLLI2SR,I2SDIV,ODD
const u16 I2S_PSC_TBL[][5]=
{{800 ,100,2,24,0},		//8Khz采样率{1102,429,4,19,0},		//11.025Khz采样率 {1600,213,2,13,0},		//16Khz采样率{2205,429,4, 9,1},		//22.05Khz采样率{3200,213,2, 6,1},		//32Khz采样率{4410,271,2, 6,0},		//44.1Khz采样率{4800,100,2, 4,0},		//48Khz采样率{8820,316,2, 3,1},		//88.2Khz采样率{9600,344,2, 3,1},  	//96Khz采样率{17640,361,2,2,0},  	//176.4Khz采样率 {19200,393,2,2,0},  	//192Khz采样率
};  
//设置IIS的采样率(@MCKEN)
//samplerate:采样率,单位:Hz
//返回值:0,设置成功;1,无法设置.
u8 I2S2_SampleRate_Set(u32 samplerate)
{ u8 i=0; u32 tempreg=0;samplerate/=10;//缩小10倍   for(i=0;i<(sizeof(I2S_PSC_TBL)/10);i++)//看看改采样率是否可以支持{if(samplerate==I2S_PSC_TBL[i][0])break;}RCC_PLLI2SCmd(DISABLE);//先关闭PLLI2Sif(i==(sizeof(I2S_PSC_TBL)/10))return 1;//搜遍了也找不到RCC_PLLI2SConfig((u32)I2S_PSC_TBL[i][1],(u32)I2S_PSC_TBL[i][2]);//设置I2SxCLK的频率(x=2)  设置PLLI2SN PLLI2SRRCC->CR|=1<<26;					//开启I2S时钟while((RCC->CR&1<<27)==0);		//等待I2S时钟开启成功. tempreg=I2S_PSC_TBL[i][3]<<0;	//设置I2SDIVtempreg|=I2S_PSC_TBL[i][4]<<8;	//设置ODD位tempreg|=1<<9;					//使能MCKOE位,输出MCKSPI2->I2SPR=tempreg;			//设置I2SPR寄存器 return 0;
}

后续发现音质问题解决了，可能原因（包括杂音）：

1、是采样率匹配问题，采样率设置不对一定会导致杂音、快进慢放等问题；
2、一个是单双声道问题，生成wav文件时如果声卡设备转换为双声道但是按照单声道处理就会有问题，数据量是双声道的，但是存储时处理了一半；
3、还有一个可能就是声卡设备的干扰问题，比如声卡i2s或者某些引脚接线不对导致影响数字信号采集；
4、还有发现一个问题，声卡i2s的收和发的数据长度设置不一致，比如发设置了标准的16位长度，而接收设置了16位扩展32位长度，导致i2s初始化后接收可能正常，但是发送时声卡收不到数据从而导致录音没有声音；
5、如果使用spi flash+fatfs进行音频文件写入的，那么音频波形快进样式也可能是spi flash的驱动问题导致的，正片擦除后写入时写入速度快就不会有这个问题，需要在写入前先擦除，如果写入时再擦除会影响写入速度从而影响录音；（调试时可以用示波器先确认硬件对应引脚输出的频率是否符合预期）

采样率的时钟频率F4按照下图配置即可（比如48khz的固定为258的PLLI2SN和3的PLLi2SR，不同外部输入时钟可以设置对应分频后为1MHZ，比如8MHZ的则设置8分频，25MHZ的设置为25）：

比如我这里是25MHZ的：（如果是8MHZ的则M设置为8，后面N和R固定为258和3）

4、结果

由于是音频内容不太好展示，主要是通过Audacity或者cool edit pro软件来导入原始的pcm数据进行测试，主要配置导入时的参数即可（实时测试时可以通过串口查看波形）。

结果（波形的高度和声音的大小也有关系，此外，对于48khz的音频stm32也有1%左右的采样丢失问题，会有一定的失真的问题，因此，对于人声采集一般建议还是低采样，比如8khz）：