PWM

通过 PWM 设备控制 LED 灯的亮度实现呼吸灯效果 更多...

通过 PWM 设备控制 LED 灯的亮度实现呼吸灯效果

源码

/*
 * 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);