BearPi-HM_Nano开发板基础外设开发——PWM输出

本示例将演示如何在BearPi-HM_Nano开发板上使用GPIO的PWM功能实现呼吸灯的效果

GPIO API分析

本案例主要使用了以下几个API完成GPIO输出功能

1、IoTGpioInit()

/**
 * @brief Initializes a GPIO device.
 *
 * @param id Indicates the GPIO pin number.
 * @return Returns {@link IOT_SUCCESS} if the GPIO device is initialized;
 * returns {@link IOT_FAILURE} otherwise. For details about other return values, see the chip description.
 * @since 2.2
 * @version 2.2
 */
unsigned int IoTGpioInit(unsigned int id);

描述：

初始化GPIO外设

2、IoTGpioSetFunc()

unsigned int IoTGpioSetFunc(unsigned int id, unsigned char val);

描述：

设置GPIO引脚复用功能

参数：

3、IoTGpioSetDir()

/**
 * @brief Sets the direction for a GPIO pin.
 *
 * @param id Indicates the GPIO pin number.
 * @param dir Indicates the GPIO input/output direction.
 * @return Returns {@link IOT_SUCCESS} if the direction is set;
 * returns {@link IOT_FAILURE} otherwise. For details about other return values, see the chip description.
 * @since 2.2
 * @version 2.2
 */
unsigned int IoTGpioSetDir(unsigned int id, IotGpioDir dir);

描述：

设置GPIO输出方向

参数：

4、IoTPwmInit()

/**
 * @brief Initializes a PWM device.
 *
 * @param port Indicates the port number of the PWM device.
 * @return Returns {@link IOT_SUCCESS} if the PWM device is initialized;
 * returns {@link IOT_FAILURE} otherwise. For details about other return values, see the chip description.
 * @since 2.2
 * @version 2.2
 */
unsigned int IoTPwmInit(unsigned int port);

描述： 初始化PWM功能

参数：

5、IoTPwmStart()

/**
 * @brief Starts PWM signal output from a specified port based on the given output frequency and duty cycle.
 *
 *
 *
 * @param port Indicates the port number of the PWM device.
 * @param duty Indicates the duty cycle for PWM signal output. The value ranges from 1 to 99.
 * @param freq Indicates the frequency for PWM signal output.
 * @return Returns {@link IOT_SUCCESS} if the PWM signal output is started;
 * returns {@link IOT_FAILURE} otherwise. For details about other return values, see the chip description.
 * @since 2.2
 * @version 2.2
 */
unsigned int IoTPwmStart(unsigned int port, unsigned short duty, unsigned int freq);

描述：

根据输入参数输出PWM信号。

参数：

6、IoTPwmDeinit()

/**
 * @brief Deinitializes a PWM device.
 *
 * @param port Indicates the port number of the PWM device.
 * @return Returns {@link IOT_SUCCESS} if the PWM device is deinitialized;
 * returns {@link IOT_FAILURE} otherwise. For details about other return values, see the chip description.
 * @since 2.2
 * @version 2.2
 */
unsigned int IoTPwmDeinit(unsigned int port);

描述： 初始化PWM功能

参数：

硬件设计

本案例将使用板载的LED来验证GPIO的PWM功能，在BearPi-HM_Nano开发板上LED的连接电路图如下图所示，LED的控制引脚与主控芯片的GPIO_2连接，所以需要编写软件去控制GPIO_2输出PWM波实现呼吸灯的效果。

软件设计

主要代码分析

basicPWMLedTask()为PWM测试主任务，该任务先调用 IoTGpioInit()初始化GPIO，因为LED灯的控制引脚接在GPIO_2上，所以通过调用IoTGpioSetFunc()将GPIO_2复用为PWM功能，并通过IoTPwmInit()初始化PWM2端口，最后在死循环里面间隔100us输出不同占空比的PWM波，实现呼吸灯的效果

yuchuan_basic_pwm_led.c

#include <stdio.h>
#include <unistd.h>
#include "ohos_init.h"
#include "cmsis_os2.h"
#include "iot_gpio.h"
#include "iot_gpio_ex.h"
#include "iot_pwm.h"

#define GPIO_LED 2
#define PWM_TASK_STACK_SIZE 512
#define PWM_TASK_PRIORITY 25

void basicPWMLedTask(void *argument)
{
    (void)argument;
    unsigned int i;
    uint8_t j = 0;
    //初始化GPIO
    IoTGpioInit(GPIO_LED);
    //设置GPIO的引脚功能为PWM功能
    IoTGpioSetFunc(GPIO_LED,IOT_GPIO_FUNC_GPIO_2_PWM2_OUT);
    //设置GPIO的输出方向
    IoTGpioSetDir(GPIO_LED,IOT_GPIO_DIR_OUT);
    //初始化PWM 端口
    IoTPwmInit(GPIO_LED);

    while (1)
    {
        /* code */
        for (i = 0; i < 400; i++)
        {
            /* code */
            //unsigned int IoTPwmStart(unsigned int port, unsigned short duty, unsigned int freq);
            IoTPwmStart(GPIO_LED, i, 40000);
            //IoTPwmStop(GPIO_LED);
            printf("%d Start PWM init!!!\n",i);
            usleep(100);
        }
        i = 0;

        j++;
        if (j == 5)
        {
            /* code */
            IoTPwmDeinit(GPIO_LED);
            printf("%d Delete PWM init!!!\n",j);
        }
        //usleep(100);
    }
    
}

static void yuchuanBasicPWMLed(void)
{
    osThreadAttr_t threadAttr;
    threadAttr.attr_bits = 0U;
    threadAttr.cb_mem = NULL;
    threadAttr.cb_size = 0U;
    threadAttr.stack_mem = NULL;
    threadAttr.stack_size = 0U;
    threadAttr.priority = 25;

    threadAttr.name = "PWMLedTask";
    if (osThreadNew((osThreadFunc_t)basicPWMLedTask, NULL, &threadAttr) == NULL)
    {
        /* code */
        printf("Falied to Create PWMLedTask!!!\n");
    }
    
}

APP_FEATURE_INIT(yuchuanBasicPWMLed);

编译调试

//applications/sample/BearPi/BearPi-HM_Nano/sample/B3_YuchuanBasicPWM

static_library("yuchuanPWM"){
    sources = [
        "yuchuan_basic_pwm_led.c",
    ]

    include_dirs = [
        "//base/iot_hardware/peripheral/interfaces/kits",
        "//kernel/liteos_m/kal/cmsis",
        "//utils/native/lite/include",
    ]
}

修改 BUILD.gn 文件

修改applications\BearPi\BearPi-HM_Nano\sample 路径下 BUILD.gn 文件，指定 yuchuanPWM参与编译。

# Copyright (c) 2020 Nanjing Xiaoxiongpai Intelligent Technology Co., Ltd.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import("//build/lite/config/component/lite_component.gni")

lite_component("sample") {
    features = [
        #"A1_kernal_thread:thread_example",
        #"A2_kernel_timer:timer_example",
        #"A3_kernel_event:event_example",
        #"A4_kernel_mutex:mutex_example",
        #"A5_kernel_semaphore:semaphore_example",
        #"A6_kernel_message:message_example",

        #"B1_basic_led_blink:led_example",
        "B2_basic_button:button_example",
        #"B3_basic_pwm_led:pwm_example",
        #"B4_basic_adc:adc_example", 
        #"B5_basic_i2c_nfc:i2c_example",
        #"B6_basic_uart:uart_example",
        
        #"C1_e53_sf1_mq2:e53_sf1_example",
        #"C2_e53_ia1_temp_humi_pls:e53_ia1_example",
        #"C3_e53_sc1_pls:e53_sc1_example",
        #"C4_e53_sc2_axis:e53_sc2_example",
        #"C5_e53_is1_infrared:e53_is1_example",

        #"D1_iot_wifi_ap:wifi_ap",
        #"D2_iot_wifi_sta_connect:wifi_sta_connect",        
        #"D3_iot_udp_client:udp_client",
        #"D4_iot_tcp_server:tcp_server",
        #"D5_iot_mqtt:iot_mqtt",        
        #"D6_iot_cloud_oc:oc_mqtt",
        #"D7_iot_cloud_onenet:onenet_mqtt",
        #"D8_iot_cloud_oc_smoke:cloud_oc_smoke",
        #"D9_iot_cloud_oc_light:cloud_oc_light",
        #"D10_iot_cloud_oc_manhole_cover:cloud_oc_manhole_cover",
        #"D11_iot_cloud_oc_infrared:cloud_oc_infrared",
        #"D12_iot_cloud_oc_agriculture:cloud_oc_agriculture",
        #"D13_iot_cloud_oc_gps:cloud_oc_gps",
        #"A1_YuchuanThread:yuchuanThread",
        #"A2_YuchuanTimer:yuchuanTimer",
        #"A4_YuchuanMutex:yuchuanMutex",
        #"A5_YuchuanSemaphore:yuchuanSemaphore",
        #"A3_YuchuanEvent:yuchuanEvent",
        #"A6_YuchuanMessage:yuchuanMessageQueue",
        "B3_YuchuanBasicPWM:yuchuanPWM",
    ]
}

运行结果

示例代码编译烧录代码后，按下开发板的RESET按键，开发板开始正常工作，LED开始不断变化亮度，实现呼吸灯的效果。