Raspberry Pi I2C

Question

我有多个使用 I2C 来回通信的 arduino。主机写两个字节，然后读回 1 个字节的响应。一切都很好，万岁。但现在我一直在努力将我的 master 切换到 Raspberry Pi。我编写的代码没有问题，但每 200 个中有 1 个 read/write，它 return 偶尔会出现错误读取，这将严重影响系统的可靠性。我附上我的代码，以防万一有人看到我做错了什么，或者如果其他人运行之前遇到过类似问题。

RPi C++代码：

#include <iostream>
#include <fstream>
#include <unistd.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include "../HaMiD_Lib/StopWatch.h"

using namespace std;

int file_i2c;
int length;
uint8_t buffer[2] = {0};

int timingLoopFreq = 500;       
int timingLoopMicroSeconds = 1000000 / timingLoopFreq;      //500 us
StopWatch loopTime(timingLoopMicroSeconds);                 // My own stopwatch livrary
uint8_t addr = 0x11;

using namespace std;

int main(void)
{
         //-------------- OPEN THE I2C BUS--------------------------
        char *filename = (char*)"/dev/i2c-1";
        if((file_i2c = open(filename, O_RDWR))< 0 ){
                //ERROR HANDLING: you can check errno to see what went wrong;
                cout << "Failed to open the i2c bus" << endl;
                return 0;
        }

        while(1){
                if (loopTime.check()) {
                        loopTime.reset();

                        if (ioctl(file_i2c, I2C_SLAVE, addr) < 0){
                                cout << "Failed to acquire bus access and/or talk to slave" << endl;
                                //ERROR HANDLING: you can check errno to see what went wrong;
                        }

                        // ------------- WRITE BYTES -------------
                        buffer[0] = 4;
                        buffer[1] = 0;
                        length = 2;                 //<<<<< Number of bytes to write
                        if (write(file_i2c, buffer, length) != length){                    // write() returns the number of bytes actually written, if it doesn't match then an error occurred (e.g. no response from the device)
                        // ERROR HANDLING: i2c transaction failed
                                cout << "Failed to write to the i2c bus " << endl;
                        } else {
                                    // ------------ READ BYTES -------
                                    length = 1;
                                    if (read(file_i2c, buffer, length) != length){              // read() returns the number of bytes actually read, if it doesn't match then an error occurred (e.g. no response from the device)
                                        //ERROR HANDLING: i2c transaction failed
                                        cout <<"Failed to read from the i2c bus" << endl;
                                    } else {
                                            cout << "Data read:" << buffer[0] << endl;
                                }
                        }
                }
        }
        cout << "exiting" << endl;
        return 0;
}

Arduino I2C 片段：

//I2C functions
void receiveEvent(int byteCount) {
    while (Wire.available()) {
        I2C_cmd_1st = Wire.read(); // 1 byte (maximum 256 commands)
        I2C_cmd_2nd = Wire.read(); // 1 byte (maximum 256 commands)
    }
}

void slavesRespond() {
    byte returnValue = 0;

    switch (I2C_cmd_1st) {
    case status_cmd:   // 40
        returnValue = module;
        if (module == DONE) {
            module = STOP;                  //reset the machine
        }
        break;
    case test_cmd:
        returnValue = ID;
        break;
    }
    Wire.write(returnValue);          // return response to last command
}

这里是 cout 输出的一小部分。读取的数据应始终 return 2 但有时（100 分之一）它无法从 i2c 总线读取或写入，有时（500 分之一）它 return 是一个错误的值（在下面的示例中它应该 return 2 但有时 return 3 是偶然的，也可能是 97 等）。

Data read:2
Data read:3    //This is wrong!
Data read:2
Failed to read from the i2c bus
Failed to read from the i2c bus
Data read:3    //This is wrong!
Data read:2

如有任何帮助，我们将不胜感激。有没有其他人看到过与 RPi 和 Arduino 类似的东西？接线非常简单，因为 RPi 是主机。

Answer 1

您是否尝试过在接收事件中只读取实际可用的我的数据。代码考虑到 receiveEvent 中的 byteCount 可以被 2 整除。

Answer 2

对于无法读取 i2c 总线的问题尝试

dtoverlay=i2c-gpio,i2c_gpio_sda=2,i2c_gpio_scl=3,i2c_gpio_delay_us=2,bus=1

代替

dtparam=i2c_arm=on

在 /boot/config.txt

Raspberry Pi I2C

Raspberry Pi I2C

c++

linux

arduino

raspberry-pi

i2c