PWM

通过 PWM 设备控制 LED 灯的亮度实现呼吸灯效果

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);