目录
概述
1 硬件接口介绍
2 SHT20模块
2.1 SHT20简介
2.2 SHT-20模块电路
3 I2C接口实现
3.1 FSP配置I2C
3.2 I2C驱动程序实现
4 SHT20驱动程序
4.1 SHT20驱动代码结构
4.2 源代码文件
5 测试
5.1 测试功能介绍
5.2 测试代码实现
5.3 运行代码
概述
本文主要介绍使用Renesas R7FA8D1BH (Cortex®-M85)控制SHT20的相关内容，包括SHT20的特性，使用FSP配置Renesas R7FA8D1BH的I2C接口，i2c驱动程序，还介绍了一个简单的应用案例：实时读取SHT20的温湿度数据，显示在OLED上。
1 硬件接口介绍
SHT2X与Renesas R7FA8D1BH通过I2C接口连接起来，其接口关系如下：
2 SHT20模块
2.1 SHT20简介
SHT20是由Sensirion公司推出的一款数字温湿度传感器。它采用先进的CMOSens®技术，具有高精度、低功耗和长期稳定性的特点。
SHT20的测量范围涵盖了-40℃至125℃的温度和0%至100%的湿度，精确度分别为±0.3℃和±3%RH。它使用了数字式输出接口，可以通过I2C总线进行数据通信，并支持温度和湿度的实时测量。
SHT20的封装形式小巧，尺寸为3x3x1.1mm，适合各种应用场景。它具有低功耗特性，工作电压范围为2.1V至3.6V，供电电流在典型条件下为1.2mA。此外，SHT20还具有快速响应时间和强大的抗干扰能力。
2.2 SHT-20模块电路
1）SHT20硬件接口图
2) sensor模块电路
SHT-20实物图：
3 I2C接口实现
3.1 FSP配置I2C
1) 在Pins面板上配置I2C IO port
2) 创建Stack对象
3）配置Stack的参数
3.2 I2C驱动程序实现
使用FSP完成参数配置后，生成硬件相关的配置代码，接下来需要实现I2C相关的驱动接口
1）创建bsp_i2c.c文件，编写如下代码
/*FILE NAME : bsp_i2c.cDescription: user i2c interface Author : tangmingfei2013@126.comDate : 2024/06/03*/
#include "bsp_i2c.h"
#include "hal_data.h"#define TIME_OUT 10000i2c_master_event_t g_i2c_callback_event;void sci_b_i2c_master_callback (i2c_master_callback_args_t * p_args)
{if (NULL != p_args){g_i2c_callback_event = p_args->event;}
} void i2c2_init_para( uint32_t const slaveAddress )
{fsp_err_t err;err = R_SCI_B_I2C_Open(&g_i2c0_ctrl, &g_i2c0_cfg);assert(FSP_SUCCESS == err);err = R_SCI_B_I2C_SlaveAddressSet(&g_i2c0_ctrl, slaveAddress, I2C_MASTER_ADDR_MODE_7BIT);assert(FSP_SUCCESS == err);
}void i2c2_write_bytes(uint8_t *pbuff, uint16_t length )
{unsigned int timeout_ms = TIME_OUT;fsp_err_t err;err = R_SCI_B_I2C_Write(&g_i2c0_ctrl, pbuff, length, false);assert(FSP_SUCCESS == err);g_i2c_callback_event = I2C_MASTER_EVENT_ABORTED;/* Since there is nothing else to do, block until Callback triggers*/while ((I2C_MASTER_EVENT_TX_COMPLETE != g_i2c_callback_event) && timeout_ms){R_BSP_SoftwareDelay(1U, BSP_DELAY_UNITS_MILLISECONDS);timeout_ms--;;}
}void i2c2_read_bytes(uint8_t *pbuff, uint16_t length )
{unsigned int timeout_ms = TIME_OUT;fsp_err_t err;g_i2c_callback_event = I2C_MASTER_EVENT_ABORTED;err = R_SCI_B_I2C_Read(&g_i2c0_ctrl, pbuff, length, false);assert(FSP_SUCCESS == err);/* Since there is nothing else to do, block until Callback triggers*/while ((I2C_MASTER_EVENT_RX_COMPLETE != g_i2c_callback_event) && timeout_ms){R_BSP_SoftwareDelay(1U, BSP_DELAY_UNITS_MILLISECONDS);timeout_ms--;;}
}/* End of this file */2）创建bsp_i2c.h文件，编写如下代码：
/*FILE NAME : bsp_i2c.hDescription: user i2c interface Author : tangmingfei2013@126.comDate : 2024/06/03*/#ifndef BSP_I2C_H#define BSP_I2C_H#include "hal_data.h"void i2c2_init_para( uint32_t const slaveAddress );
void i2c2_write_bytes(uint8_t *pbuff, uint16_t length );
void i2c2_read_bytes(uint8_t *pbuff, uint16_t length );#endif /* BSP_I2C_H */4 SHT20驱动程序
4.1 SHT20驱动代码结构
1）写寄存器函数
2）读寄存器函数
3）sensor初始化函数
4）获取温度值函数
5) 获取湿度值函数
4.2 源代码文件
1）创建sht2x.c文件，编写如下代码
/*FILE NAME : sht2x.cDescription: user sht20 interface Author : tangmingfei2013@126.comDate : 2024/06/03*/
#include "hal_data.h"
#include "sht2x.h"/******************************************************************************
* LOCAL MACROS AND DEFINITIONS
******************************************************************************/
#define SHT2X_ADDR 0x40
#define POLY 0x131 //P(x)=x^8+x^5+x^4+1 = 100110001#define DELAY_CNT 4500 //for N32G45, sleep time is 6.4 ms #define QUERY_TEMP_CMD TRIG_T_MEASUREMENT_HM
#define QUERY_HUMIDY_CMD TRIG_RH_MEASUREMENT_HMstatic void msleep(unsigned int time)
{uint16_t i;for (i = 0; i < time; i++);
}static int sht2xdrv_CheckCrc(unsigned char data[], unsigned char nbrOfBytes, unsigned char checksum)
{uint16_t res = 0;uint16_t crc = 0;uint16_t byteCtr;//calculates 8-Bit checksum with given polynomialfor (byteCtr = 0; byteCtr < nbrOfBytes; ++byteCtr){crc ^= (data[byteCtr]);for (uint8_t bit = 8; bit > 0; --bit){if (crc & 0x80){crc = (crc << 1) ^ POLY;}else{crc = (crc << 1);}}}if (crc != checksum){res = 1;}return res;
}static int sht2xdrv_CalcTemperatureC(int u16sT)
{int temperatureC; // variable for resultu16sT &= ~0x0003; // clear bits [1..0] (status bits)/** Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,* optimized for integer fixed point (3 digits) arithmetic*/temperatureC = ((17572 * u16sT) >> 16) - 4685;return temperatureC;
}static int sht2xdrv_CalcRH(int u16sRH)
{int humidityRH; // variable for resultu16sRH &= ~0x0003; // clear bits [1..0] (status bits)/** Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,* optimized for integer fixed point (3 digits) arithmetic*/humidityRH = ((12500 * u16sRH) >> 16) - 600;return humidityRH;
}static uint8_t write_reg( uint8_t *buff, uint8_t len )
{fsp_err_t err;err = R_SCI_B_I2C_SlaveAddressSet( &g_i2c0_ctrl, SHT2X_ADDR, I2C_MASTER_ADDR_MODE_7BIT);assert(FSP_SUCCESS == err);i2c2_write_bytes(buff, len);return 0;
}static uint8_t read_regs(uint8_t reg, uint8_t *buf, uint8_t len)
{fsp_err_t err;uint8_t msgs[2];err = R_SCI_B_I2C_SlaveAddressSet( &g_i2c0_ctrl, SHT2X_ADDR, I2C_MASTER_ADDR_MODE_7BIT);assert(FSP_SUCCESS == err);msgs[0] = reg;i2c2_write_bytes(msgs, 1);i2c2_read_bytes( buf, len);return 0;
}int sht2x_softreset( void )
{int ret = -1;unsigned char buf[2] = {0};unsigned char cmd = SOFT_RESET;buf[0] = cmd;ret = write_reg(buf, 1);if( ret < 0 ){printf("%s %s write softrest cmd to sht2x failure \n", __FILE__, __FUNCTION__);return -1;}msleep(50);return 0;
}int sht2x_get_temperature( float *temper)
{unsigned char buf[4] = {0}, checksum;int ret = -1;int tempval;ret = read_regs(QUERY_TEMP_CMD, buf, 3);if( ret < 0 ){printf("get the temper failure.\n");return -1;}// match crc herechecksum = buf[2];ret = sht2xdrv_CheckCrc(buf, 2, checksum);if( ret < 0 ){printf("match check sum error.\n");return -1;}tempval = (buf[0] << 8) | buf[1];*temper = (float)sht2xdrv_CalcTemperatureC( tempval );return 0;
}int sht2x_get_humidy( float *humidy )
{unsigned char buf[4] = {0}, checksum;int ret = -1;int tempval;ret = read_regs(QUERY_HUMIDY_CMD, buf, 3);if( ret < 0 ){printf("get the humidy failure.\n");return -1;}// match crc herechecksum = buf[2];ret = sht2xdrv_CheckCrc(buf, 2, checksum);if( ret < 0 ){printf("match check sum error.\n");return -1;}tempval = (buf[0] << 8) | buf[1];*humidy = (float)sht2xdrv_CalcRH( tempval );return 0;
}void sht2x_Init( void )
{ fsp_err_t err;err = R_SCI_B_I2C_SlaveAddressSet( &g_i2c0_ctrl, SHT2X_ADDR, I2C_MASTER_ADDR_MODE_7BIT);assert(FSP_SUCCESS == err);sht2x_softreset();
}2）创建sht2x.h文件，编写如下代码
/*FILE NAME : sht2x.hDescription: user sht20 interface Author : tangmingfei2013@126.comDate : 2024/06/03*/
#ifndef __SHT20_H
#define __SHT20_H#ifdef __cplusplus
extern "C" {
#endif#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <string.h>
#include <time.h>typedef enum sht2xOptErrorCode
{SHT2x_RES_I2C_ERR = 0X01,
}sht2xOptErrorCode;/******************************************************************************
* EXPORTED MACROS AND DEFINITIONS
******************************************************************************/
typedef enum sht2xResolution_t
{SHT2x_RES_12_14BIT = 0x00, // RH=12bit, T=14bitSHT2x_RES_8_12BIT = 0x01, // RH= 8bit, T=12bitSHT2x_RES_10_13BIT = 0x80, // RH=10bit, T=13bitSHT2x_RES_11_11BIT = 0x81, // RH=11bit, T=11bitSHT2x_RES_MASK = 0x81 // Mask for res. bits (7,0) in user reg.
} sht2xResolution_t;typedef enum sht2xStatusCode {SHT2x_STATUS_OK = 0x00,SHT2x_STATUS_VALID_DATA = 0x01,SHT2x_STATUS_NO_CHANGE = 0x02,SHT2x_STATUS_ABORTED = 0x03,SHT2x_STATUS_BUSY = 0x04,SHT2x_STATUS_SUSPEND = 0x05,SHT2x_STATUS_ERR_IO = 0x06,SHT2x_STATUS_ERR_BAD_DATA = 0x07,SHT2x_STATUS_ERR_TIMEOUT = 0x08
}sht2xStatusCode;// sensor command
typedef enum{TRIG_T_MEASUREMENT_HM = 0xE3, // command trig. temp meas. hold masterTRIG_RH_MEASUREMENT_HM = 0xE5, // command trig. humidity meas. hold masterTRIG_T_MEASUREMENT_POLL = 0xF3, // command trig. temp meas. no hold masterTRIG_RH_MEASUREMENT_POLL = 0xF5, // command trig. humidity meas. no hold masterUSER_REG_W = 0xE6, // command writing user registerUSER_REG_R = 0xE7, // command reading user registerSOFT_RESET = 0xFE // command soft reset
}sht2xCommand_t;typedef enum {SHT2x_EOB_ON = 0x40, // end of batterySHT2x_EOB_MASK = 0x40, // Mask for EOB bit(6) in user reg.
} sht2xEob_t;typedef enum {SHT2x_HEATER_ON = 0x04, // heater onSHT2x_HEATER_OFF = 0x00, // heater offSHT2x_HEATER_MASK = 0x04, // Mask for Heater bit(2) in user reg.
} etSHT2xHeater;// measurement signal selection
typedef enum{HUMIDITY,TEMP
}etSHT2xMeasureType;typedef enum{I2C_ADR_W = 128, // sensor I2C address + write bitI2C_ADR_R = 129 // sensor I2C address + read bit
}etI2cHeader;typedef struct {unsigned char _step;unsigned char ret;unsigned char finish; //1: finished, 0: idleunsigned char dataValid; //1: valid, 0: invalidint _tryCnt;int _binValue; // primordial value from sht20 register int outValue; // true temperature or humidity
} shtdrv;typedef struct {shtdrv st_Temp;shtdrv st_RH;int errorCode;
}shtOpt;void sht2x_Init( void );
int sht2x_get_humidy( float *humidy );
int sht2x_get_temperature( float *temper);#ifdef __cplusplus
}
#endif#endif /* __SHT20_H */
5 测试
5.1 测试功能介绍
1) 实时读取SHT2X的数据，并将数据转换为温度和湿度值
2）采样间隔为1 second
3) 在OLED上实时显示温度和湿度数据
5.2 测试代码实现
代码189行： 获取RTC时间值
代码190行：判断1s时间间隔
代码193行：获取湿度数据
代码194行：获取温度数据
代码198~209： 在OLED上实时显示温度和湿度数据
5.3 运行代码
测试环境如下：
编译代码，并将代码下载到板卡中，其运行结果如下：
