RPi wiingpi读取i2c失败

Question

我有一个AHT21，通过i2c通信:我发送3个字节，得到6。arduino草图可以工作，但RPi不行。WiringPi i2c语法有什么问题?我想把这个arduino草图转换成RPi c++程序使用WiringPi。如此:

#include <Wire.h>
#define AHT21 0x38
void setup() {
// put your setup code here, to run once:
Wire.begin(); // the SDA and SCL
Serial.begin(9600);
uint8_t rawData[7] = {0,0,0,0,0,0,0};
Wire.beginTransmission(AHT21);
Wire.write(0xAC);  //send measurement command, start measurement
Wire.write(0x33);  //send measurement control
Wire.write(0x00);  //send measurement NOP control
Wire.endTransmission();
delay(100);
Wire.requestFrom(AHT21, 6);
for (uint8_t i = 0; i < 6; i++)
{
rawData[i] = Wire.read();
Serial.print(i);Serial.print(": ");
Serial.println(rawData[i]);
}
}
void loop() {}
Gives:
0: 28
1: 106
2: 90
3: 117
4: 126
5: 70

这个RPI代码一遍又一遍地给出状态字节失败:

#include <wiringPi.h>
#include <wiringPiI2C.h>
#include <stdio.h>
#include <stdint.h>
#include <math.h>
#define Address 0x38
int main (int argc, char **argv)
{
int fd = wiringPiI2CSetup(Address);
uint8_t rawData[7] = {0,0,0,0,0,0,0};
wiringPiI2CWrite(fd,0xAC);  //send measurement command, start measurement
wiringPiI2CWrite(fd,0x33);  //send measurement control
wiringPiI2CWrite(fd,0x00);  //send measurement NOP control
delay(100);
for (uint8_t i = 0; i < 6; i++)
{
rawData[i] = wiringPiI2CRead(fd);
printf("%d: %dn",i,rawData[i]);
}
}
Gives:
./aht21 
0: 28
1: 28
2: 28
3: 28
4: 28
5: 28

Answer 1

我放弃了WiringPi，使用了ioctl和i2c-dev.h。没问题:

//gcc -g -Wall -Wextra -pedantic -std=c11 -D_DEFAULT_SOURCE -D_BSD_SOURCE -o aht21 aht21.c
#include <stdio.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>    // read/write usleep
#include <stdlib.h>    // exit function
#include <inttypes.h>  // uint8_t, etc
#include <linux/i2c-dev.h> // I2C bus definitions
int main (int argc, char **argv)
{
float  ahtTemp, ahtHum;
uint8_t rawData[7] = {0, 0, 0, 0, 0, 0, 0};
// Create I2C bus
int fd;
char *bus = "/dev/i2c-1";
if ((fd = open(bus, O_RDWR)) < 0)
{
printf("Failed to open the bus. n");
exit(1);
}
// Get I2C device,
ioctl(fd, I2C_SLAVE, 0x38);
char TriggerCMD[3] = {0};
TriggerCMD[0] = 0xAC;
TriggerCMD[1] = 0x33;
TriggerCMD[2] = 0x00;
write(fd, TriggerCMD, 3);
sleep(1);
if (read(fd, rawData, 7) != 7)
{
printf("Error : Input/Output Error n");
}
else
{
uint32_t humidity = rawData[1];            //20-bit raw humidity data
humidity <<= 8;
humidity  |= rawData[2];
humidity <<= 4;
humidity  |= rawData[3] >> 4;
uint32_t temperature = rawData[3] & 0x0F;   //20-bit raw temperature data
temperature <<= 8;
temperature  |= rawData[4];
temperature <<= 8;
temperature  |= rawData[5];

ahtHum = ((float)humidity / 0x100000) * 100.0;
ahtTemp = (((float)temperature / 0x100000) * 200.0 - 50.0) * 1.8 + 32.0;
printf("%.2f,%.2fn", ahtHum, ahtTemp);
}
close(fd);
}