/*********************************************************************************
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* Copyright: (C) 2022 Guo Wenxue <guowenxue@gmail.com>
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* All rights reserved.
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*
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* Filename: sht20.c
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* Description: This file is temperature and relative humidity sensor SHT20 code
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*
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* Version: 1.0.0(2022/4/14)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "2022/04/14 12:13:26"
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*
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********************************************************************************/
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/*
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* Hardware connection:
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*
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* Sht20 Module RaspberryPi/IGKBoard
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* VCC <-----> 3.3V
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* SDA <-----> SDA
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* SCL <-----> SCL
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* GND <-----> GND
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*/
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#include <stdio.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include <linux/types.h>
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#include <sys/stat.h>
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#include <linux/i2c-dev.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <string.h>
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#include <stdint.h>
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#include <time.h>
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#include <errno.h>
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#include <string.h>
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#define SOFTRESET 0xFE
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#define TRIGGER_TEMPERATURE_NO_HOLD 0xF3
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#define TRIGGER_HUMIDITY_NO_HOLD 0xF5
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static inline void msleep(unsigned long ms);
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static inline void dump_buf(const char *prompt, uint8_t *buf, int size);
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int sht2x_init(char *i2c_dev);
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int sht2x_get_serialnumber(int fd, uint8_t *serialnumber, int size);
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int sht2x_get_temp_humidity(int fd, float *temp, float *rh);
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int main(int argc, char **argv)
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{
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int fd;
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float temp;
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float rh;
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uint8_t serialnumber[8];
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if( argc != 2)
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{
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printf("This program used to do I2C test by sht20 temperature & humidity module.\n");
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printf("Usage: %s /dev/i2c-x\n", argv[0]);
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return 0;
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}
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fd = sht2x_init(argv[1]);
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if(fd < 0)
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{
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printf("SHT2x initialize failure\n");
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return 1;
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}
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if( sht2x_get_serialnumber(fd, serialnumber, 8) < 0)
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{
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printf("SHT2x get serial number failure\n");
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return 3;
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}
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if( sht2x_get_temp_humidity(fd, &temp, &rh) < 0 )
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{
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printf("SHT2x get get temperature and relative humidity failure\n");
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return 3;
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}
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printf("Temperature=%lf ℃ relative humidity=%lf.\n", temp, rh);
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close(fd);
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}
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static inline void msleep(unsigned long ms)
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{
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struct timespec cSleep;
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unsigned long ulTmp;
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cSleep.tv_sec = ms / 1000;
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if (cSleep.tv_sec == 0)
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{
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ulTmp = ms * 10000;
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cSleep.tv_nsec = ulTmp * 100;
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}
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else
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{
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cSleep.tv_nsec = 0;
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}
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nanosleep(&cSleep, 0);
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}
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static inline void dump_buf(const char *prompt, uint8_t *buf, int size)
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{
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int i;
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if( !buf )
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{
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return ;
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}
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if( prompt )
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{
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printf("%s ", prompt);
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}
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for(i=0; i<size; i++)
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{
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printf("%02x ", buf[i]);
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}
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printf("\n");
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return ;
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}
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int sht2x_softreset(int fd)
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{
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uint8_t buf[4];
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if( fd<0 )
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{
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printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
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return -1;
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}
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/* software reset SHT2x */
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memset(buf, 0, sizeof(buf));
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buf[0] = SOFTRESET;
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write(fd, buf, 1);
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msleep(50);
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return 0;
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}
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int sht2x_init(char *i2c_dev)
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{
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int fd;
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if( (fd=open(i2c_dev, O_RDWR)) < 0)
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{
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printf("i2c device open failed: %s\n", strerror(errno));
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return -1;
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}
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/* set I2C mode and SHT2x slave address */
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ioctl(fd, I2C_TENBIT, 0); /* Not 10-bit but 7-bit mode */
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ioctl(fd, I2C_SLAVE, 0x40); /* set SHT2x slava address 0x40*/
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if( sht2x_softreset(fd) < 0 )
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{
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printf("SHT2x softreset failure\n");
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return -2;
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}
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return fd;
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}
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int sht2x_get_temp_humidity(int fd, float *temp, float *rh)
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{
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uint8_t buf[4];
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if( fd<0 || !temp || !rh )
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{
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printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
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return -1;
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}
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/* send trigger temperature measure command and read the data */
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memset(buf, 0, sizeof(buf));
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buf[0]=TRIGGER_TEMPERATURE_NO_HOLD;
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write(fd, buf, 1);
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msleep(85); /* datasheet: typ=66, max=85 */
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memset(buf, 0, sizeof(buf));
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read(fd, buf, 3);
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dump_buf("Temperature sample data: ", buf, 3);
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*temp = 175.72 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 46.85;
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/* send trigger humidity measure command and read the data */
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memset(buf, 0, sizeof(buf));
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buf[0] = TRIGGER_HUMIDITY_NO_HOLD;
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write(fd, buf, 1);
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msleep(29); /* datasheet: typ=22, max=29 */
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memset(buf, 0, sizeof(buf));
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read(fd, buf, 3);
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dump_buf("Relative humidity sample data: ", buf, 3);
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*rh = 125 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 6;
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return 0;
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}
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int sht2x_get_serialnumber(int fd, uint8_t *serialnumber, int size)
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{
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uint8_t buf[4];
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if( fd<0 || !serialnumber || size!=8 )
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{
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printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
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return -1;
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}
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/* Read SerialNumber from Location 1 */
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memset(buf, 0, sizeof(buf));
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buf[0] = 0xfa; /* command for readout on-chip memory */
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buf[1] = 0x0f; /* on-chip memory address */
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write(fd, buf, 2);
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memset(buf, 0, sizeof(buf));
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read(fd, buf, 4);
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serialnumber[5]=buf[0]; /* Read SNB_3 */
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serialnumber[4]=buf[1]; /* Read SNB_2 */
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serialnumber[3]=buf[2]; /* Read SNB_1 */
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serialnumber[2]=buf[3]; /* Read SNB_0 */
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/* Read SerialNumber from Location 2 */
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memset(buf, 0, sizeof(buf) );
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buf[0]=0xfc; /* command for readout on-chip memory */
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buf[1]=0xc9; /* on-chip memory address */
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write(fd, buf, 2);
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memset(buf, 0, sizeof(buf) );
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read(fd, buf, 4);
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serialnumber[1]=buf[0]; /* Read SNC_1 */
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serialnumber[0]=buf[1]; /* Read SNC_0 */
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serialnumber[7]=buf[2]; /* Read SNA_1 */
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serialnumber[6]=buf[3]; /* Read SNA_0 */
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dump_buf("SHT2x Serial number: ", serialnumber, 8);
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return 0;
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}
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