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| #include <stdio.h> #include <linux/types.h> #include <fcntl.h> #include <unistd.h> #include <stdlib.h> #include <sys/types.h> #include <sys/ioctl.h> #include <errno.h> #include <assert.h> #include <string.h> #include <linux/i2c.h> #include <linux/i2c-dev.h> #define I2C_DEV_NAME "/dev/i2c-5" unsigned int fd; int func_write_regs(unsigned char devaddr,unsigned char reg, unsigned char *buf) { struct i2c_rdwr_ioctl_data work_queue; int ret; work_queue.nmsgs = 1; work_queue.msgs = (struct i2c_msg *)malloc(work_queue.nmsgs * sizeof(work_queue.msgs)); if (!work_queue.msgs) { printf("memory alloc failed"); ret = -1; return ret; } work_queue.nmsgs = 1; (work_queue.msgs0).len = 2; // buf的长度，要写的字节数+1字节地址 (work_queue.msgs0).flags = 0; // write (work_queue.msgs0).addr = devaddr; //设备地址 (work_queue.msgs0).buf = (unsigned char *)malloc(2); (work_queue.msgs0).buf0 = reg; //写的地址 memcpy(&work_queue.msgs0.buf1, buf, 1); //你要写的数据 ret = ioctl(fd, I2C_RDWR, (unsigned long)&work_queue); if (ret < 0) printf("error during I2C_RDWR ioctl with error code %d\n", ret); free((work_queue.msgs0).buf); free(work_queue.msgs); return ret; } int func_read_regs(unsigned char devaddr,unsigned char reg, unsigned char *read_data) { struct i2c_rdwr_ioctl_data work_queue; int ret; work_queue.nmsgs = 1; /* 消息数量 */ work_queue.msgs = (struct i2c_msg *)malloc(work_queue.nmsgs * sizeof(work_queue.msgs)); if (!work_queue.msgs) { printf("Memory alloc error\n"); close(fd); return -1; } (work_queue.msgs0).len = 1; (work_queue.msgs0).flags = 0; //写数据的标志位 (work_queue.msgs0).addr = devaddr; (work_queue.msgs0).buf = (unsigned char *)malloc(1); (work_queue.msgs0).buf0 = reg; ret = ioctl(fd, I2C_RDWR, (unsigned long)&work_queue); if (ret < 0) { printf("error during I2C_RDWR ioctl with error code %d\n", ret); return ret; } (work_queue.msgs0).len = 1; (work_queue.msgs0).flags = 1; //读数据的标志位 (work_queue.msgs0).addr = devaddr; ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue); if (ret < 0) { printf("Error during I2C_RDWR ioctl with error code: %d\n", ret); return ret; } else { // printf("read val:%02x\n", (work_queue.msgs0).buf0); *read_data=work_queue.msgs0.buf0; } free(work_queue.msgs0.buf); free(work_queue.msgs); return ret; } int main() { int ret; char write_value=0x03; char read_value; fd = open(I2C_DEV_NAME, O_RDWR); if (fd < 0) { perror(I2C_DEV_NAME); printf("can not open i2c device %s\n", I2C_DEV_NAME); exit(0); } ret = func_write_regs(0x32, 0x80, & write_value); if (ret < 0) { printf("write error! \n"); close(fd); return ret; } usleep(100000); ret = func_read_regs(0x32, 0x94, & read_value); if (ret < 0) { printf("read error! \n"); close(fd); return ret; } printf("read val:%02x\r\n", read_value); close(fd); return 0; } |
这段代码主要分为三部分，定义了三个函数，用于通过i2c总线将一个字节0x24写入设备地址0x32上的寄存器0x16中，之后从相同设备的0x16寄存器读取数据并打印出来。
1. 第一部分
定义了函数func_write_regs，用于向设备写入寄存器数据。该函数首先创建了一个i2c_rdwr_ioctl_data类型的结构体变量work_queue，用于存储i2c通信的信息。然后，通过动态内存分配为work_queue.msgs分配了足够的内存空间，用于存储i2c通信所需的消息。之后，设置了要写入数据的相关信息，并调用ioctl函数执行i2c写操作。最后，释放动态分配的内存，并返回执行结果。
2.第二部分
定义了函数func_read_regs，用于从设备读取寄存器数据。过程与func_write_regs类似，首先创建了一个i2c_rdwr_ioctl_data类型的结构体变量work_queue，并为work_queue.msgs分配了动态内存。然后，先发送一个写操作的消息，设置要读取的寄存器地址，然后再发送一个读操作的消息，从设备读取数据。最后，将读取到的数据拷贝到buf中，并释放动态分配的内存，返回执行结果。
3.第三部分
打开i2c5，向0x32设备的寄存器0x16写入0x24，延时100毫秒等待写操作完成，读取0x32设备的寄存器0x16，并以十六进制格式打印。