在Android源码树中平添userspace I2C读写工具（i2c-util）
在Android源码树中添加userspace I2C读写工具（i2c-util）by @宋宝华Barry通过/dev/i2c-n节点，用户可以在use
在Android源码树中添加userspace I2C读写工具（i2c-util）
by @宋宝华Barry
通过/dev/i2c-n节点，用户可以在userspace直接访问板上的i2c外设寄存器，主要是透过I2C_RDWR这个IO控制命令将i2c_msg数组传递给kernel去执行。下面的代码可以完成这个功能：
#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> /* This is the structure as used in the I2C_RDWR ioctl call */ struct i2c_rdwr_ioctl_data { struct i2c_msg __user *msgs; /* pointers to i2c_msgs */ __u32 nmsgs; /* number of i2c_msgs */ }; int i2c_read_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len) { struct i2c_rdwr_ioctl_data work_queue; unsigned char w_val = reg_address; int ret; int fd = open(dev, O_RDWR); if (!fd) { printf("Error on opening the device file\n"); return 0; } work_queue.nmsgs = 2; work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct i2c_msg)); if (!work_queue.msgs) { printf("Memory alloc error\n"); close(fd); return 0; } ioctl(fd, I2C_TIMEOUT, 2); ioctl(fd, I2C_RETRIES, 1); (work_queue.msgs[0]).len = 1; (work_queue.msgs[0]).addr = slave_address; (work_queue.msgs[0]).buf = &w_val; (work_queue.msgs[1]).len = len; (work_queue.msgs[1]).flags = I2C_M_RD; (work_queue.msgs[1]).addr = slave_address; (work_queue.msgs[1]).buf = buf; ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue); if (ret < 0) { printf("Error during I2C_RDWR ioctl with error code: %d\n", ret); close(fd); free(work_queue.msgs); return 0; } else { printf("read salve:%02x reg:%02x\n", slave_address, reg_address); close(fd); free(work_queue.msgs); return len; } } int i2c_write_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len) { struct i2c_rdwr_ioctl_data work_queue; unsigned char w_val = reg_address; unsigned char w_buf[len+1]; int ret; w_buf[0] = reg_address; int fd = open(dev, O_RDWR); if (!fd) { printf("Error on opening the device file\n"); return 0; } work_queue.nmsgs = 1; work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct i2c_msg)); if (!work_queue.msgs) { printf("Memory alloc error\n"); close(fd); return 0; } ioctl(fd, I2C_TIMEOUT, 2); ioctl(fd, I2C_RETRIES, 1); (work_queue.msgs[0]).len = 1 + len; (work_queue.msgs[0]).addr = slave_address; (work_queue.msgs[0]).buf = w_buf; memcpy(w_buf + 1, buf, len); ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue); if (ret < 0) { printf("Error during I2C_RDWR ioctl with error code: %d\n", ret); close(fd); free(work_queue.msgs); return 0; } else { printf("write salve:%02x reg:%02x\n", slave_address, reg_address); close(fd); free(work_queue.msgs); return len; } } int main(int argc, char **argv) { unsigned int fd; unsigned int slave_address, reg_address; unsigned r_w; unsigned w_val; unsigned char rw_val; if (argc < 5) { printf("Usage:\n%s /dev/i2c-x start_addr reg_addr rw[0|1] [write_val]\n", argv[0]); return 0; } fd = open(argv[1], O_RDWR); if (!fd) { printf("Error on opening the device file %s\n", argv[1]); return 0; } sscanf(argv[2], "%x", &slave_address); sscanf(argv[3], "%x", ?_address); sscanf(argv[4], "%d", &r_w); if (r_w == 0) { i2c_read_reg(argv[1], &rw_val, slave_address, reg_address, 1); printf("Read %s-%x reg %x, read value:%x\n", argv[1], slave_address, reg_address, rw_val); } else { if (argc < 6) { printf("Usage:\n%s /dev/i2c-x start_addr reg_addr r|w[0|1] [write_val]\n", argv[0]); return 0; } sscanf(argv[5], "%d", &w_val); if ((w_val & ~0xff) != 0) printf("Error on written value %s\n", argv[5]); rw_val = (unsigned char)w_val; i2c_write_reg(argv[1], &rw_val, slave_address, reg_address, 1); } return 0; } 在android/external/新建i2c-util目录，上述源代码存入android/external/i2c-util/i2c-util.c，编写对应的Android.mk:[plain] view plaincopy- LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS)
- LOCAL_MODULE_TAGS := optional
- LOCAL_MODULE := i2c-util
- LOCAL_SRC_FILES += \
- i2c-util.c \
- include $(BUILD_EXECUTABLE)
编译Android后，上述工具会位于/system/bin目录。在电路板上使用它：[plain] view plaincopy- / # i2c-rw /dev/i2c-2 0x38 0x1 0 read salve:38 reg:01 value:12
- / # / # i2c-rw /dev/i2c-2 0x38 0x2 0
- read salve:38 reg:02 value:81
