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luckfox-pico-sdk/sysdrv/source/mcu/rt-thread/components/drivers/hwtimer/README_CN.md
luckfox-eng29 8f34c2760d project:build.sh: Added fastboot support; custom modifications to U-Boot and kernel implemented using patches. 
project:cfg:BoardConfig_IPC: Added fastboot BoardConfig file and firmware post-scripts, distinguishing between
the BoardConfigs for Luckfox Pico Pro and Luckfox Pico Max. project:app: Added fastboot_client and rk_smart_door
for quick boot applications; updated rkipc app to adapt to the latest media library. media:samples: Added more
usage examples. media:rockit: Fixed bugs; removed support for retrieving data frames from VPSS. media:isp:
Updated rkaiq library and related tools to support connection to RKISP_Tuner. sysdrv:Makefile: Added support for
compiling drv_ko on Luckfox Pico Ultra W using Ubuntu; added support for custom root filesystem.
sysdrv:tools:board: Updated Buildroot optional mirror sources, updated some software versions, and stored device
tree files and configuration files that undergo multiple modifications for U-Boot and kernel separately.
sysdrv:source:mcu: Used RISC-V MCU SDK with RT-Thread system, mainly for initializing camera AE during quick
boot. sysdrv:source:uboot: Added support for fastboot; added high baud rate DDR bin for serial firmware upgrades.
sysdrv:source:kernel: Upgraded to version 5.10.160; increased NPU frequency for RV1106G3; added support for
fastboot.

Signed-off-by: luckfox-eng29 <eng29@luckfox.com>
2024-10-14 09:47:04 +08:00

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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。