[I2C]pca9555应用层测试代码

/aaronLinux/p/6896573.html

如果在设置I2C_SLAVE的时候，提示device_busy，可以使用I2C_SLAVE_FORCE, 在驱动里面二者对应同一个case语句

应用层可以调用接口：i2c_smbus_write_word_data(fd, __, __);和i2c_smbus_read_word_data(fd,__);

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/questions/9974592/i2c-slave-ioctl-purpose

问题如下：

1. 应用程序中直接fd句柄是整个I2C0总线的文件句柄，而只是在set地址的时候，将I2C address设置下去，后面操作该芯片还是操作全局I2C0总线上这个文件，并没有指定去操作该芯片，这其中是怎么做到的？这样的话，如果在一个main程序中， 操作同一总线上不同i2c设备，而文件句柄是同一个，这要如何操作？

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驱动方面：

首先配置I2C内核驱动，将pca9555的源码built-in进入(这里根据需要可能要配thermal的驱动)，然后在devicetree中根据pca9555硬件I2C地址配置节点。

测试源码：

// I2C test program for a PCA9555#include <stdint.h>#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <linux/i2c-dev.h>#include <sys/types.h>#include <sys/stat.h>#include <sys/ioctl.h>#include <fcntl.h>// I2C Linux device handleint g_i2cFile;// open the Linux devicevoid i2cOpen(){ g_i2cFile = open("/dev/i2c-0", O_RDWR); if (g_i2cFile < 0) { perror("i2cOpen"); exit(1); }}// close the Linux devicevoid i2cClose(){ close(g_i2cFile);}// set the I2C slave address for all subsequent I2C device transfersvoid i2cSetAddress(int address){ if (ioctl(g_i2cFile, I2C_SLAVE, address) < 0) { perror("i2cSetAddress"); exit(1); }}// write a 16 bit value to a register pair// write low byte of value to register reg,// and high byte of value to register reg+1void pca9555WriteRegisterPair(uint8_t reg, uint16_t value){ uint8_t data[3]; data[0] = reg; data[1] = value & 0xff; data[2] = (value >> 8) & 0xff; if (write(g_i2cFile, data, 3) != 3) { perror("pca9555SetRegisterPair"); }}// read a 16 bit value from a register pairuint16_t pca9555ReadRegisterPair(uint8_t reg){ uint8_t data[3]; data[0] = reg; if (write(g_i2cFile, data, 1) != 1) { perror("pca9555ReadRegisterPair set register"); } if (read(g_i2cFile, data, 2) != 2) { perror("pca9555ReadRegisterPair read value"); } return data[0] | (data[1] << 8);}// set IO ports to input, if the corresponding direction bit is 1,// otherwise set it to outputvoid pca9555SetInputDirection(uint16_t direction){ pca9555WriteRegisterPair(6, direction);}// set the IO port outputsvoid pca9555SetOutput(uint16_t value){ pca9555WriteRegisterPair(2, value);}// read the IO port inputsuint16_t pca9555GetInput(){ return pca9555ReadRegisterPair(0);}int main(int argc, char** argv){ // test output value int v = 3; // direction of the LED animation int directionLeft = 1; // open Linux I2C device i2cOpen(); // set address of the PCA9555 i2cSetAddress(0x20); // set input for IO pin 15, rest output pca9555SetInputDirection(1 << 15); // LED animation loop while (1) { // if button is pressed, invert output int xor; if (pca9555GetInput() & 0x8000) { xor = 0; } else { xor = 0xffff; } // set current output pca9555SetOutput(v ^ xor); // animate LED position if (directionLeft) { v <<= 1; } else { v >>= 1; } if (v == 0x6000) { directionLeft = 0; } if (v == 3) { directionLeft = 1; } // wait 100 ms for next animation step usleep(100000); } // close Linux I2C device i2cClose(); return 0;}