一、pwm设备概念
rtthread将pwm设备抽象成rt_device_pwm
二、pwm api
设置pwm的周期和脉冲宽度时间后可以使/失能pwm设备。
//查找pwm设备
/*
name：pwm设备名称
*/
rt_device_t rt_device_find(const char* name);
//设置pwm设备的周期和占空比
/*
device：pwm设备句柄
channel：pwm通道
period：周期
pulse：脉冲宽度时间
*/
rt_err_t rt_pwm_set(struct rt_device_pwm *device,
int channel,
rt_uint32_t period,
rt_uint32_t pulse);
//使能pwm设备
/*
device：pwm设备句柄
channel：通道
*/
rt_err_t rt_pwm_enable(struct rt_device_pwm *device, int channel);
//关闭pwm设备
/*
device：pwm设备句柄
channel：通道
*/
rt_err_t rt_pwm_disable(struct rt_device_pwm *device, int channel);
三、pwm示例
/*
* Copyright (c) 2006-2018, RT-Thread Development Team
*
* SPDX-License-Identifier: Apache-2.0
*
* Change Logs:
* Date Author Notes
* 2018-11-25 misonyo first implementation.
*/
/*
* 程序清单：这是一个 PWM 设备使用例程
* 例程导出了 pwm_led_sample 命令到控制终端
* 命令调用格式：pwm_led_sample
* 程序功能：通过 PWM 设备控制 LED 灯的亮度，可以看到LED不停的由暗变到亮，然后又从亮变到暗。
*/
#include <rtthread.h>
#include <rtdevice.h>
#define LED_PIN_NUM 57 /* LED PIN脚编号，查看驱动文件drv_gpio.c确定 */
#define PWM_DEV_NAME "pwm3" /* PWM设备名称 */
#define PWM_DEV_CHANNEL 4 /* PWM通道 */
struct rt_device_pwm *pwm_dev; /* PWM设备句柄 */
static int pwm_led_sample(int argc, char *argv[])
{
rt_uint32_t period, pulse, dir;
period = 500000; /* 周期为0.5ms，单位为纳秒ns */
dir = 1; /* PWM脉冲宽度值的增减方向 */
pulse = 0; /* PWM脉冲宽度值，单位为纳秒ns */
/* 设置LED引脚脚模式为输出 */
rt_pin_mode(LED_PIN_NUM, PIN_MODE_OUTPUT);
/* 拉高LED引脚 */
rt_pin_write(LED_PIN_NUM, PIN_HIGH);
/* 查找设备 */
pwm_dev = (struct rt_device_pwm *)rt_device_find(PWM_DEV_NAME);
if (pwm_dev == RT_NULL)
{
rt_kprintf("pwm sample run failed! can't find %s device!\n", PWM_DEV_NAME);
return RT_ERROR;
}
/* 设置PWM周期和脉冲宽度默认值 */
rt_pwm_set(pwm_dev, PWM_DEV_CHANNEL, period, pulse);
/* 使能设备 */
rt_pwm_enable(pwm_dev, PWM_DEV_CHANNEL);
while (1)
{
rt_thread_mdelay(50);
if (dir)
{
pulse += 5000; /* 从0值开始每次增加5000ns */
}
else
{
pulse -= 5000; /* 从最大值开始每次减少5000ns */
}
if (pulse >= period)
{
dir = 0;
}
if (0 == pulse)
{
dir = 1;
}
/* 设置PWM周期和脉冲宽度 */
rt_pwm_set(pwm_dev, PWM_DEV_CHANNEL, period, pulse);
}
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(pwm_led_sample, pwm sample);