98 lines
2.1 KiB
Markdown
98 lines
2.1 KiB
Markdown
|
# 定时器设备
|
|||
|
|
|
|||
|
|
## 功能
|
|||
|
|
|
|||
|
|
* 时间测量
|
|||
|
|
* 周期或单次执行回调函数
|
|||
|
|
|
|||
|
|
## 编译
|
|||
|
|
|
|||
|
|
1. 在rtconfig.h添加 `#define RT_USING_HWTIMER`
|
|||
|
|
|
|||
|
|
## 使用流程
|
|||
|
|
|
|||
|
|
1. 以读写方式打开设备
|
|||
|
|
2. 设置超时回调函数（如果需要）
|
|||
|
|
3. 根据需要设置定时模式（单次/周期）
|
|||
|
|
4. 设置计数频率（可选）
|
|||
|
|
5. 写入超时值，定时器随即启动
|
|||
|
|
6. 停止定时器（可选）
|
|||
|
|
7. 关闭设备（如果需要）
|
|||
|
|
|
|||
|
|
应用参考 [hwtimer_test] (/examples/test/hwtimer\_test.c)
|
|||
|
|
|
|||
|
|
## 驱动编写指南
|
|||
|
|
|
|||
|
|
### 操作接口
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
struct rt_hwtimer_ops
|
|||
|
|
{
|
|||
|
|
void (*init)(struct rt_hwtimer_device *timer, rt_uint32_t state);
|
|||
|
|
rt_err_t (*start)(struct rt_hwtimer_device *timer, rt_uint32_t cnt, rt_hwtimer_mode_t mode);
|
|||
|
|
void (*stop)(struct rt_hwtimer_device *timer);
|
|||
|
|
rt_uint32_t (*count_get)(struct rt_hwtimer_device *timer);
|
|||
|
|
rt_err_t (*control)(struct rt_hwtimer_device *timer, rt_uint32_t cmd, void *args);
|
|||
|
|
};
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
* init - state <1 打开设备 0 关闭设备>
|
|||
|
|
* start - cnt <超时值> - mode <单次/周期>
|
|||
|
|
* stop - <停止计数>
|
|||
|
|
* count_get - <读取计数器值>
|
|||
|
|
* control - <设置计数频率 >
|
|||
|
|
|
|||
|
|
### 定时器特征信息
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
struct rt_hwtimer_info
|
|||
|
|
{
|
|||
|
|
rt_int32_t maxfreq;
|
|||
|
|
rt_int32_t minfreq;
|
|||
|
|
rt_uint32_t maxcnt;
|
|||
|
|
rt_uint8_t cntmode;
|
|||
|
|
};
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
* maxfreq <设备支持的最大计数频率>
|
|||
|
|
* minfreq <设备支持的最小计数频率>
|
|||
|
|
* maxcnt <计数器最大计数值>
|
|||
|
|
* cntmode <递增计数/递减计数>
|
|||
|
|
|
|||
|
|
### 注册设备
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
static rt_hwtimer_t _timer0;
|
|||
|
|
int stm32_hwtimer_init(void)
|
|||
|
|
{
|
|||
|
|
_timer0.info = &_info;
|
|||
|
|
_timer0.ops = &_ops;
|
|||
|
|
|
|||
|
|
rt_device_hwtimer_register(&_timer0, "timer0", TIM2);
|
|||
|
|
|
|||
|
|
return 0;
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### 定时器中断
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
void timer_irq_handler(void)
|
|||
|
|
{
|
|||
|
|
//其它操作
|
|||
|
|
|
|||
|
|
rt_device_hwtimer_isr(&_timer0);
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 注意事项
|
|||
|
|
|
|||
|
|
**可能出现定时误差**
|
|||
|
|
|
|||
|
|
误差原因：
|
|||
|
|
|
|||
|
|
假设计数器最大值0xFFFF，计数频率1Mhz，定时时间1秒又1微秒。
|
|||
|
|
|
|||
|
|
由于定时器一次最多只能计时到65535us，对于1000001us的定时要求。
|
|||
|
|
可以50000us定时20次完成，此时将会出现计算误差1us。
|