/aaronLinux/p/6896573.html
注意点：
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,__);
分享：
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
#include
#include
#include
#include
#include
#include
#include
#include
//I2C Linux device handle
int g_i2cFile;
//open the Linux device
void i2cOpen()
{
g_i2cFile = open("/dev/i2c-0", O_RDWR);
if (g_i2cFile < 0) {
perror("i2cOpen");
exit(1);
}
}
//close the Linux device
void i2cClose()
{
close(g_i2cFile);
}
//set the I2C slave address for all subsequent I2C device transfers
void 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+1
void 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 pair
uint16_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 output
void pca9555SetInputDirection(uint16_t direction)
{
pca9555WriteRegisterPair(6, direction);
}
//set the IO port outputs
void pca9555SetOutput(uint16_t value)
{
pca9555WriteRegisterPair(2, value);
}
//read the IO port inputs
uint16_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;
}
