- 之前插入的是i2c的第四条总线，所以需要在设备树中的I2C-4节点中增加pca9685节点。
- 需要编写一个i2c_client的驱动，使得设备能够被检测到并且注册进内核。
- 需要编写一个i2c_device的驱动，使得可以对设备进行一个操作，完成各种通信指令和操作
- 需要编写一个App应用程序，用来调试和测试驱动的完整性，一个简单的demo
自己做下来发现1和2实现其中一种应该就能注册驱动设备。
二、设备树编写设备树编写的代码：
&i2c4 { //将设备写进i2c4中
pca9685: pca9685@40 { //@40是设备的地址
compatible = "nxp,pca9685"; //这是用来匹配的字符串
reg = <0x40>; //reg存放设备树地址，不带读写
};
};
三、device_client编写
使用i2c_board_info来注册i2c设备的方式在3.0之前使用的比较多。现在可以使用设备树了更方便。
#include四、device_driver编写#include #include #include struct i2c_client *pca9685_client; struct i2c_board_info pca9685_info = { .type = "pca9685", .addr = 0x40, }; const unsigned short addr_list[] = { 0x40, I2C_CLIENT_END }; static int i2c_client_pca9685_init(void) { struct i2c_adapter *adapter; adapter = i2c_get_adapter(4); //获取i2c4的i2c_adapter if(!adapter) { printk(KERN_ERR"i2c_get_adapter(4) fialedn"); return -EINVAL; } pca9685_client = i2c_new_device(adapter, &pca9685_info); //把i2c_board_info注册进adapter中，返回一个i2c_client if(!pca9685_client) { printk(KERN_ERR"can't create i2c device %sn", pca9685_info.type); return -EINVAL; } i2c_put_adapter(adapter); //应该是更新一下adapter，因为有新设备的信息加进入去了 return 0; } static void i2c_client_pca9685_exit(void) { i2c_unregister_device(pca9685_client); //所以这里卸载的是对应的i2c_client } module_init(i2c_client_pca9685_init); module_exit(i2c_client_pca9685_exit); MODULE_AUTHOR("chentuo"); MODULE_LICENSE("GPL");
通过之前的i2c-tool测试，驱动需要使用前需要做一下初始化
- 复位，寄存器0x00写0
i2cset -f -y I2CBUS CHIP-ADDRESS 0x00 0x0 b - 读取芯片的MODE1的内容
- 把MODE1的前7位清零，并且设置低5位为1
- 往PRE_SCALE寄存器里，写入需要输出的PWM预分频值
- 把MODE1的值恢复到睡眠之前
- 延迟5ms
- 往MODE1写入1010 0001(b)，这里低5位是自增模式需要注意是否需要开启
如何修改引脚的PWM波：
- 设置LEDx_ON_L和LEDx_ON_H的值，x是第几号输出引脚，ON寄存器有高寄存器和低寄存器，组合在一起就是PWM上升的位置
- 设置LEDx_OFF_L和LEDx_OFF_H的值，x是第几号输出引脚，OFF寄存器有高寄存器和低寄存器，组合在一起就是PWM下降的位置
- 总的细分应该是4096，十六进制表示就是0x0FFF
#include五、device_test编写#include #include #include #include #include #include #define PCA9685_MODE1 0x00 #define PCA9685_PRESCALE 0xFE #define LED0_ON_L 0x06 #define LED0_ON_H 0x07 #define LED0_OFF_L 0x08 #define LED0_OFF_H 0x09 static int pca9685_major = 0; static struct class *pca9685_class; static struct i2c_client *pca9685_client; static const struct of_device_id of_match_ids_pca9685[] = { { .compatible = "nxp,pca9685", .data = NULL }, { } }; static const struct i2c_device_id pca9685_ids[] = { { "pca9685", (kernel_ulong_t)NULL }, { } }; int pca9685_i2c_write(struct i2c_client *client, uint8_t reg_addr, uint8_t data) { struct i2c_msg msg; uint8_t txbuf[] = {reg_addr, data}; int ret = -1; msg.flags = !I2C_M_RD; msg.addr = client->addr; msg.len = 2; msg.buf = txbuf; ret = i2c_transfer(client->adapter, &msg, 1); return ret; } static uint8_t pca9685_i2c_read(struct i2c_client *client, uint8_t reg_addr) { struct i2c_msg msgs[2]; uint8_t rxbuf[1]; msgs[0].flags = !I2C_M_RD; msgs[0].addr = client->addr; msgs[0].len = 1; msgs[0].buf = ®_addr; msgs[1].flags = I2C_M_RD; msgs[1].addr = client->addr; msgs[1].len = 1; msgs[1].buf = rxbuf; i2c_transfer(client->adapter, msgs, 2); return rxbuf[0]; } static void setPWMFreq(uint8_t freq) { float pre_scale_val; uint8_t prescale = 0; uint8_t old_mode = 0; uint8_t new_mode = 0; pre_scale_val = 25000000.0/(4096*freq*0.915); prescale = (uint8_t)(pre_scale_val+0.5)-1; old_mode = pca9685_i2c_read(pca9685_client, PCA9685_MODE1); new_mode = (old_mode&0x7F) | 0x10; //sleep pca9685_i2c_write(pca9685_client, PCA9685_MODE1, new_mode); //go to sleep pca9685_i2c_write(pca9685_client, PCA9685_PRESCALE, prescale); //set the prescaler old_mode = old_mode & 0xEF; pca9685_i2c_write(pca9685_client, PCA9685_MODE1, old_mode); mdelay(5); pca9685_i2c_write(pca9685_client, PCA9685_MODE1, old_mode | 0xa1); } static void setPWM(uint8_t num, uint16_t on, uint16_t off) { pca9685_i2c_write(pca9685_client, LED0_ON_L+4*num, on); pca9685_i2c_write(pca9685_client, LED0_ON_L+4*num+1, on>>8); pca9685_i2c_write(pca9685_client, LED0_ON_L+4*num+2, off); pca9685_i2c_write(pca9685_client, LED0_ON_L+4*num+3, off>>8); } int pca9685_open(struct inode *inode, struct file *file) { return 0; } ssize_t pca9685_read(struct file *file, char __user *buf, size_t size, loff_t *offset) { char kernel_buf[6]; int err = 0; err = copy_to_user(buf, kernel_buf, size); return size; } ssize_t pca9685_write(struct file *file, const char __user *buf, size_t size, loff_t *offset) { int err = -1; int value; err = copy_from_user(&value, buf, sizeof(int)); if(value > 2000) value = 2000; if(value < 1000) value = 1000; setPWM(0, 0, value/5); return 0; } //int (*release) (struct inode *, struct file *); static struct file_operations pca9685_ops = { .owner = THIS_MODULE, .open = pca9685_open, // .read = pca9685_read, .write = pca9685_write, }; int pca9685_probe(struct i2c_client *client, const struct i2c_device_id *id) { printk(KERN_ERR "pca9685: probe.n"); pca9685_client = client; pca9685_major = register_chrdev(0, "pca9685", &pca9685_ops); if(pca9685_major < 0) { printk(KERN_ERR "pca9685: couldn't get a major number.n"); return -1; } pca9685_class = class_create(THIS_MODULE, "pca9685_class"); if(IS_ERR(pca9685_class)) { printk(KERN_ERR "pca9685 class: create failed.n"); unregister_chrdev(pca9685_major, "pca9685"); return -1; } device_create(pca9685_class, NULL, MKDEV(pca9685_major, 0), NULL, "pca9685"); // reset(); setPWMFreq(50); return 0; } int pca9685_remove(struct i2c_client *client) { printk(KERN_ERR "pca9685: remove.n"); device_destroy(pca9685_class, MKDEV(pca9685_major, 0)); class_destroy(pca9685_class); unregister_chrdev(pca9685_major, "pca9685"); return 0; } static struct i2c_driver i2c_driver_pca9685 = { .driver = { .name = "pca9685", .of_match_table = of_match_ids_pca9685, }, .probe = pca9685_probe, .remove = pca9685_remove, .id_table = pca9685_ids, }; static int __init pca9685_init(void) { int ret = i2c_add_driver(&i2c_driver_pca9685); printk(KERN_ERR "pca9685: init.n"); return ret; } static void __exit pca9685_exit(void) { i2c_del_driver(&i2c_driver_pca9685); printk(KERN_ERR "pca9685: exit.n"); } module_init(pca9685_init); module_exit(pca9685_exit); MODULE_AUTHOR("chentuo"); MODULE_LICENSE("GPL");
#include#include #include #include #include #include #include int main(int argc, char *argv[]) { int fd; int on; printf("hello worldn"); fd = open("/dev/pca9685", O_RDWR); if(fd < 0) { printf("can not open filen"); return -1; } if(argc != 2) { printf("usage: %s [1000~2000]n", argv[0]); return -1; } on = atoi(argv[1]); write(fd, &on, sizeof(int)); close(fd); return 0; }
