Create aht20.c

aht20.c

@@ -0,0 +1,93 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <linux/i2c-dev.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <pigpio.h>
+
+#define AHT20_STATUSBIT_BUSY = 7 # The 7th bit is the Busy indication bit. 1 = Busy, 0 = not.
+#define AHT20_I2CADDR 0X38
+unsigned char AHT20_CMD_STATUS[2] = {AHT20_I2CADDR<<1|0,0x71};
+unsigned char AHT20_CMD_SOFTRESET[2] = {AHT20_I2CADDR<<1|0,0xBA};
+unsigned char AHT20_CMD_INITIALIZE[4] = {AHT20_I2CADDR<<1|0, 0xBE, 0x08, 0x00};
+unsigned char AHT20_CMD_MEASURE[4] = {AHT20_I2CADDR<<1|0,0xAC, 0x33, 0x00};
+unsigned char AHT20_CMD_READ[1] = {AHT20_I2CADDR<<1|1};
+
+int handle;
+unsigned char AHT20_GET_STATUS()
+{
+ unsigned char value;
+ i2cWriteDevice(handle, AHT20_CMD_STATUS, sizeof(AHT20_CMD_STATUS));
+ value = i2cReadByte(handle);
+ if(value&0x18!=0x18) 
+ {
+ fprintf(stderr,"Device not found, bad status. should be 0x18 and is %0.2x\n",value);
+ }
+
+ //printf( "%0.2x\n", value);
+ return value;
+}
+void aht20_measure(float * temperature, float * humidity)
+{
+ int i;
+ int r;
+ char aout;
+ unsigned char command[2];
+ unsigned char value[4];
+ unsigned char str[8];
+ unsigned char status;
+
+ // loop in case it is occupied elseware
+ while (gpioInitialise() < 0) {
+ perror("gpioInitialise failed: "); 
+ sleep(1);
+ }
+ handle = i2cOpen(1, AHT20_I2CADDR, 0);
+ if(handle < 0)
+ {
+ perror("Could not open the I2C device: ");
+ exit(-1);
+ }
+
+ status=AHT20_GET_STATUS();
+
+ usleep(40000);
+ //i2cWriteDevice(handle, AHT20_CMD_SOFTRESET, sizeof(AHT20_CMD_SOFTRESET));
+ //usleep(20000);
+ if((status & 0x08) !=0x08)
+ {
+ i2cWriteDevice(handle, AHT20_CMD_INITIALIZE, sizeof(AHT20_CMD_INITIALIZE));
+ usleep(10000);
+ }
+
+ i2cWriteDevice(handle, AHT20_CMD_MEASURE, sizeof(AHT20_CMD_MEASURE));
+ while ((AHT20_GET_STATUS()&0x80) == 0x80) usleep(80000);
+ i2cWriteDevice(handle,AHT20_CMD_READ,sizeof(AHT20_CMD_READ));
+ i2cReadDevice(handle,value,7);
+
+ *humidity = (value[1] << 12) | (value[2] << 4) | (value[3] >> 4);
+ *humidity = *humidity * 100 / pow(2,20);
+
+ *temperature = ((value[3] & 0xF) << 16) | (value[4] << 8) | value[5];;
+ *temperature = *temperature / (pow(2,20))*200-50;
+
+ i2cClose(handle);
+ gpioTerminate();
+
+}
+
+#if defined testing
+int main(int argc, char *argv[])
+{
+ float temperature, humidity;
+ while ( 1 )
+ {
+ aht20_measure(&temperature, &humidity);
+ printf("Temperature=%f\n",temperature);
+ printf("Humidity=%f\n",humidity);
+ sleep(1);
+ }
+}
+#endif