mirror of https://github.com/OpenIPC/firmware.git
111 lines
4.1 KiB
C
111 lines
4.1 KiB
C
#include <stdio.h>
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#include <sys/ioctl.h>
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#include <fcntl.h>
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#include <linux/i2c-dev.h>
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#include <linux/i2c.h>
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#include <unistd.h> /* add by paulerr*/
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#define CHIP "/dev/i2c-0"
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#define CHIP_ADDR 0x40 //HTU21D地址
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#define READ_TEMP 0XE3 //温度转换命令
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#define READ_HUM 0XE5 //湿度转换命令
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/* More info: https://github.com/kingmacth/Openwet-SDK/tree/master/package/HTU21D */
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unsigned char HTU21D_Check_CRC(unsigned short int message_from_sensor,unsigned char check_value_from_sensor);
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int main()
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{
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printf("hello,this is HTU21D tester \n");
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int fd =open(CHIP, O_RDWR);
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if (fd< 0) {
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printf("open"CHIP"failed \n");
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goto exit;
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}
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if (ioctl(fd,I2C_SLAVE_FORCE, CHIP_ADDR) < 0) { /*设置芯片地址 */
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printf("oictl:setslave address failed\n");
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goto close;
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}
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struct i2c_msg msg;
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unsigned char rddata[3];
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unsigned char rdaddr[2] = {0x10, 0}; /* 将要读取的数据在芯片中的偏移量 */
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unsigned char TempAddr[2] = {0xe3, 0}; /* 发送E3读取温度 */
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unsigned char HumAddr[2] = {0xE5, 0}; /* 发送E5读取湿度 */
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unsigned short int tmp_dat,CRC_Result;
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float Temp,Hum;
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/*printf("inputa char you want to write to E2PROM\n");
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wrbuf[2]= getchar();
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printf("writereturn:%d, write data:%x\n", write(fd, wrbuf, 1), wrbuf[2]);
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sleep(5);*/
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//printf("Read temp!\n",write(fd, TempAddr, 1)); /* 开启温度转换 */
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write(fd, TempAddr, 1);
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usleep(100000);
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read(fd, &rddata, 3); //读取两字节温度一字节校验
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tmp_dat=rddata[0];
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tmp_dat=tmp_dat<<8;
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tmp_dat=tmp_dat+rddata[1];
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//printf("rddata:%x%02x,%x\n", rddata[0], rddata[1],rddata[2]);
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CRC_Result=HTU21D_Check_CRC(tmp_dat,rddata[2]);
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//printf("CRC=%x,%x\n",CRC_Result ,tmp_dat);//CRC校验
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if(CRC_Result==0)
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{
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Temp=(tmp_dat*175.72)/65536-46.85;
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printf("Temp=%.2f\n",Temp);
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}
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//printf("Read hum!\n",write(fd, HumAddr, 1)); /* 开启湿度转换 */
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write(fd, HumAddr, 1);
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usleep(100000);
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read(fd, &rddata, 3); //读取两字节湿度一字节校验
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tmp_dat=rddata[0];
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tmp_dat=tmp_dat<<8;
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tmp_dat=tmp_dat+rddata[1];
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//printf("rddata:%x%02x,%x\n", rddata[0], rddata[1],rddata[2]);
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CRC_Result=HTU21D_Check_CRC(tmp_dat,rddata[2]);
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//printf("CRC=%x,%x\n",CRC_Result ,tmp_dat);//CRC校验
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if(CRC_Result==0)
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{
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Temp=(tmp_dat*125)/65536-6;
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printf("Hum=%.2f%%RH\n",Temp);
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}
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close:
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close(fd);
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exit:
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return 0;
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}
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//**************************************************************************************************************
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//两个参数一个是传感器的源数据，另一个是传感器得出的CRC校验值
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//如果校验通过返回0，不通过返回非0
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//From: http://www.nongnu.org/avr-libc/user-manual/group__util__crc.html
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//POLYNOMIAL = 0x0131 = x^8 + x^5 + x^4 + 1 : http://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks
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#define SHIFTED_DIVISOR 0x988000 //This is the 0x0131 polynomial shifted to farthest left of three bytes
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//**************************************************************************************************************
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unsigned char HTU21D_Check_CRC(unsigned short int message_from_sensor,unsigned char check_value_from_sensor)
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{
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unsigned char i;
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//Test cases from datasheet:
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//message = 0xDC, checkvalue is 0x79
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//message = 0x683A, checkvalue is 0x7C
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//message = 0x4E85, checkvalue is 0x6B
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unsigned int remainder = (unsigned int)message_from_sensor << 8; //Pad with 8 bits because we have to add in the check value
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unsigned int divsor = (unsigned int)SHIFTED_DIVISOR;
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remainder |= check_value_from_sensor; //Add on the check value
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for (i = 0 ; i < 16 ; i++) //Operate on only 16 positions of max 24. The remaining 8 are our remainder and should be zero when we're done.
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{
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if( remainder & (unsigned int)1<<(23 - i) ) //Check if there is a one in the left position
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remainder ^= divsor;
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divsor>>=1;//Rotatethedivsormax16timessothatwehave8bitsleftofaremainder
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}
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return(unsigned char)remainder;
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}
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