/*********************************************************************************
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* Copyright: (C) 2023 LingYun IoT System Studio
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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(10/08/23)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "10/08/23 17:52:00"
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*
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* Pin connection:
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* STH20 Module Raspberry Pi Board
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* VCC <-----> #Pin1(3.3V)
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* SDA1 <-----> #Pin3(SDA, BCM GPIO2)
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* SCL1 <-----> #Pin5(SCL, BCM GPIO3)
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* GND <-----> GND
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*
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* /boot/config.txt:
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* dtoverlay=i2c1,pins_2_3
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*
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********************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include <libgen.h>
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#include <getopt.h>
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#include <time.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <linux/types.h>
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#include <linux/i2c.h>
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#include <linux/i2c-dev.h>
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#include "logger.h"
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#include "util_proc.h"
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#include "sht20.h"
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int i2c_write(int fd, uint8_t slave_addr, uint8_t *data, int len);
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int i2c_read(int fd, uint8_t slave_addr, uint8_t *buf, int size);
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int sht20_checksum(uint8_t *data, int len, int8_t checksum);
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int sht2x_get_temp_humidity(float *temp, float *rh)
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{
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int fd;
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int rv = 0;
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char *dev = SHT20_I2CDEV;
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uint8_t buf[4];
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if( !temp || !rh )
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{
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log_error("Invalid input arguments\n");
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return -1;
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}
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/*+--------------------------------+
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*| open /dev/i2c-x device |
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*+--------------------------------+*/
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if( (fd=open(dev, O_RDWR)) < 0)
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{
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log_error("i2c device '%s' open failed: %s\n", dev, strerror(errno));
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return -2;
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}
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/*+--------------------------------+
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*| software reset SHT20 sensor |
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*+--------------------------------+*/
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buf[0] = 0xFE;
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i2c_write(fd, SHT20_I2CADDR, buf, 1);
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msleep(50);
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/*+--------------------------------+
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*| trigger temperature measure |
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*+--------------------------------+*/
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buf[0] = 0xF3;
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i2c_write(fd, SHT20_I2CADDR, 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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i2c_read(fd, SHT20_I2CADDR, buf, 3);
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log_dump(LOG_LEVEL_DEBUG, "Temperature sample data: ", buf, 3);
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if( !sht20_checksum(buf, 2, buf[2]) )
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{
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rv = -3;
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log_error("Temperature sample data CRC checksum failure.\n");
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goto cleanup;
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}
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*temp = 175.72 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 46.85;
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/*+--------------------------------+
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*| trigger humidity measure |
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*+--------------------------------+*/
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buf[0] = 0xF5;
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i2c_write(fd, SHT20_I2CADDR, 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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i2c_read(fd, SHT20_I2CADDR, buf, 3);
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log_dump(LOG_LEVEL_DEBUG, "Relative humidity sample data: ", buf, 3);
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if( !sht20_checksum(buf, 2, buf[2]) )
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{
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rv = -4;
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log_error("Relative humidity sample data CRC checksum failure.\n");
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goto cleanup;
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}
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*rh = 125 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 6;
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/*+--------------------------------+
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*| print the measure result |
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*+--------------------------------+*/
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log_debug("Temperature=%lf 'C relative humidity=%lf%%\n", *temp, *rh);
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cleanup:
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close(fd);
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return rv;
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}
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int sht20_checksum(uint8_t *data, int len, int8_t checksum)
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{
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int8_t crc = 0;
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int8_t bit;
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int8_t byteCtr;
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//calculates 8-Bit checksum with given polynomial: x^8 + x^5 + x^4 + 1
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for (byteCtr = 0; byteCtr < len; ++byteCtr)
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{
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crc ^= (data[byteCtr]);
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for ( bit = 8; bit > 0; --bit)
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{
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/* x^8 + x^5 + x^4 + 1 = 0001 0011 0001 = 0x131 */
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if (crc & 0x80) crc = (crc << 1) ^ 0x131;
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else crc = (crc << 1);
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}
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}
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if (crc != checksum)
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return 0;
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else
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return 1;
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}
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int i2c_write(int fd, uint8_t slave_addr, uint8_t *data, int len)
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{
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struct i2c_rdwr_ioctl_data i2cdata;
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int rv = 0;
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if( !data || len<= 0)
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{
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log_error("%s() invalid input arguments!\n", __func__);
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return -1;
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}
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i2cdata.nmsgs = 1;
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i2cdata.msgs = malloc( sizeof(struct i2c_msg)*i2cdata.nmsgs );
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if ( !i2cdata.msgs )
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{
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log_error("%s() msgs malloc failed!\n", __func__);
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return -2;
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}
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i2cdata.msgs[0].addr = slave_addr;
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i2cdata.msgs[0].flags = 0; //write
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i2cdata.msgs[0].len = len;
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i2cdata.msgs[0].buf = malloc(len);
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if( !i2cdata.msgs[0].buf )
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{
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log_error("%s() msgs malloc failed!\n", __func__);
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rv = -3;
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goto cleanup;
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}
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memcpy(i2cdata.msgs[0].buf, data, len);
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if( ioctl(fd, I2C_RDWR, &i2cdata)<0 )
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{
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log_error("%s() ioctl failure: %s\n", __func__, strerror(errno));
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rv = -4;
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goto cleanup;
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}
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cleanup:
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if( i2cdata.msgs[0].buf )
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free(i2cdata.msgs[0].buf);
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if( i2cdata.msgs )
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free(i2cdata.msgs);
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return rv;
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}
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int i2c_read(int fd, uint8_t slave_addr, uint8_t *buf, int size)
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{
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struct i2c_rdwr_ioctl_data i2cdata;
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int rv = 0;
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if( !buf || size<= 0)
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{
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log_error("%s() invalid input arguments!\n", __func__);
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return -1;
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}
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i2cdata.nmsgs = 1;
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i2cdata.msgs = malloc( sizeof(struct i2c_msg)*i2cdata.nmsgs );
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if ( !i2cdata.msgs )
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{
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log_error("%s() msgs malloc failed!\n", __func__);
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return -2;
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}
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i2cdata.msgs[0].addr = slave_addr;
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i2cdata.msgs[0].flags = I2C_M_RD; //read
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i2cdata.msgs[0].len = size;
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i2cdata.msgs[0].buf = buf;
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memset(buf, 0, size);
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if( ioctl(fd, I2C_RDWR, &i2cdata)<0 )
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{
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log_error("%s() ioctl failure: %s\n", __func__, strerror(errno));
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rv = -4;
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}
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free( i2cdata.msgs );
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return rv;
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}
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