[文章]基于小凌派RK2206开发板：OpenHarmony如何使用IoT接口控制PWM外设

1、案例简介

本案例是在小凌派-RK2206开发板上使用IoT库PWM接口，进行PWM编程开发。

例程将创建一个任务，每隔5秒将PWM0~10依次启用，输出1000Hz。

例程源代码：https://gitee.com/Lockzhiner-Electronics/lockzhiner-rk2206-openharmony3.0lts/tree/master/vendor/lockzhiner/rk2206/samples/b16_iot_pwm

2、基础知识

PWM在日常设备中非常常见，以下我们将演示IoT库的PWM接口如何进行PWM控制。

2.1、头文件

base/iot_hardware/peripheral/interfaces/kits/iot_pwm.h

2.2、初始化PWM设备：IoTPwmInit

unsigned int IoTPwmInit(unsigned int port);

描述：

初始化PWM设备。

参数：

其中，port对应于如下表所示：

返回值：

实现：

hal_iot_pwm.c文件在device/rockchip/rk2206/adapter/hals/iot_hardware/wifiiot_lite目录下。

unsigned int IoTPwmInit(unsigned int port)
{
    unsigned int ret = 0;
​
    if (port >= EPWMDEV_MAX) {
        PRINT_ERR("port(%d) >= EPWMDEV_MAX(%d)\\n", port, EPWMDEV_MAX);
        return IOT_FAILURE;
    }
​
    PinctrlSet(m_pwm_bus_info[port].pwm_bus.pwm.gpio,
        m_pwm_bus_info[port].pwm_bus.pwm.func,
        m_pwm_bus_info[port].pwm_bus.pwm.type,
        m_pwm_bus_info[port].pwm_bus.pwm.drv);
    PwmIoInit(m_pwm_bus_info[port].pwm_bus);
    LzPwmInit(m_pwm_bus_info[port].port);
​
    return IOT_SUCCESS;
}

2.3、取消初始化PWM设备：IoTPwmDeinit

unsigned int IoTPwmDeinit(unsigned int port);

描述：

取消初始化PWM设备。

参数：

其中，port对应于如下表所示：

返回值：

实现：

hal_iot_pwm.c文件在device/rockchip/rk2206/adapter/hals/iot_hardware/wifiiot_lite目录下。

unsigned int IoTPwmDeinit(unsigned int port)
{
    if (port >= EPWMDEV_MAX) {
        PRINT_ERR("port(%d) >= EPWMDEV_MAX(%d)\\n", port, EPWMDEV_MAX);
        return IOT_FAILURE;
    }
​
    LzGpioDeinit(m_pwm_bus_info[port].pwm_bus.pwm.gpio);
​
    LzPwmDeinit(m_pwm_bus_info[port].port);
  
    return IOT_SUCCESS;
}

2.4、开始PWM信号输出：IoTPwmStart

unsigned int IoTPwmStart(unsigned int port, unsigned short duty, unsigned int freq);

描述：

开始PWM信号输出。

参数：

其中，port对应于如下表所示：

返回值：

实现：

hal_iot_pwm.c文件在device/rockchip/rk2206/adapter/hals/iot_hardware/wifiiot_lite目录下。

unsigned int IoTPwmStart(unsigned int port, unsigned short duty, unsigned int freq)
{
#define DUTY_MIN        1
#define DUTY_MAX        99
#define SEC_TO_NSEC     (1000000000UL)
    unsigned int duty_ns;
    unsigned int cycle_ns;
  
    if (port >= EPWMDEV_MAX) {
        PRINT_ERR("port(%d) >= EPWMDEV_MAX(%d)\\n", port, EPWMDEV_MAX);
        return IOT_FAILURE;
    }
    if ((duty < DUTY_MIN) || (DUTY_MAX < duty)) {
        PRINT_ERR("duty(%d) out of the range(%d ~ %d)\\n", duty, DUTY_MIN, DUTY_MAX);
        return IOT_FAILURE;
    }
    if (freq == 0) {
        PRINT_ERR("freq(%d) is invalid!\\n", freq);
        return IOT_FAILURE;
    }
    if (freq > SEC_TO_NSEC) {
        PRINT_ERR("freq(%d) > SEC_TO_NSEC(%d)\\n", freq, SEC_TO_NSEC);
        return IOT_FAILURE;
    }
​
    cycle_ns = SEC_TO_NSEC / freq;
    duty_ns = cycle_ns * duty / 100;
​
    LzPwmStart(m_pwm_bus_info[port].port, duty_ns, cycle_ns);
​
    return IOT_SUCCESS;
}

2.5、停止PWM信号输出：IoTPwmStop

unsigned int IoTPwmStop(unsigned int port);

描述：

停止PWM信号输出。

参数：

其中，port对应于如下表所示：

返回值：

实现：

hal_iot_pwm.c文件在device/rockchip/rk2206/adapter/hals/iot_hardware/wifiiot_lite目录下。

unsigned int IoTPwmStop(unsigned int port)
{
    if (port >= EPWMDEV_MAX) {
        PRINT_ERR("port(%d) >= EPWMDEV_MAX(%d)\\n", port, EPWMDEV_MAX);
        return IOT_FAILURE;
    }
​
    LzPwmStart(m_pwm_bus_info[port].port, 0, 0);
​
    return IOT_SUCCESS;
}

3、程序设计

在pwm_example函数中，创建一个任务。

void pwm_example()
{
    unsigned int thread_id;
    TSK_INIT_PARAM_S task = {0};
    unsigned int ret      = LOS_OK;
​
    task.pfnTaskEntry = (TSK_ENTRY_FUNC)pwm_thread;
    task.uwStackSize  = 2048;
    task.pcName       = "pwm_thread";
    task.usTaskPrio   = 20;
    ret               = LOS_TaskCreate(&thread_id, &task);
    if (ret != LOS_OK) {
        printf("Falied to create pwm_thread ret:0x%x\\n", ret);
        return;
    }
}

pwm_thread任务中调用IOT库的PWM接口控制PWM。

void pwm_thread()
{
    unsigned int ret;
    /* PWM端口号对应于参考文件：
     * device/rockchip/rk2206/adapter/hals/iot_hardware/wifiiot_lite/hal_iot_pwm.c
     */
    unsigned int port = 0;
​
    while (1) {
        printf("===========================\\n");
        printf("PWM(%d) Init\\n", port);
        ret = IoTPwmInit(port);
        if (ret != 0) {
            printf("IoTPwmInit failed(%d)\\n");
            continue;
        }
​
        printf("PWM(%d) Start\\n", port);
        ret = IoTPwmStart(port, 50, 1000);
        if (ret != 0) {
            printf("IoTPwmStart failed(%d)\\n");
            continue;
        }
​
        LOS_Msleep(5000);
​
        printf("PWM(%d) end\\n", port);
        ret = IoTPwmStop(port);
        if (ret != 0) {
            printf("IoTPwmStop failed(%d)\\n");
            continue;
        }
​
        ret = IoTPwmDeinit(port);
        if (ret != 0) {
            printf("IoTPwmInit failed(%d)\\n");
            continue;
        }
​
        printf("\\n");
​
        port++;
        if (port >= 11) {
            port = 0;
        }
    }
}

4、编译调试

**修改 **vendor/lockzhiner/rk2206/sample 路径下 BUILD.gn 文件，指定 iot_pwm_example 参与编译。

"./b16_iot_pwm:iot_pwm_example",

**修改 **device/lockzhiner/rk2206/sdk_liteos 路径下 Makefile 文件，添加 -liot_pwm_example 参与编译。

hardware_LIBS = -lhal_iothardware -lhardware -lshellcmd -liot_pwm_example

5、运行结果

示例代码编译烧录代码后，按下开发板的RESET按键，通过串口助手查看日志，任务每隔5s控制不同PWM输出。

entering kernel init...
hilog will init.
[MAIN:D]Main: LOS_Start ...
Entering scheduler
OHOS # hiview init success.===========================
PWM(0) Init
[GPIO:D]LzGpioInit: id 12 is initialized successfully
PWM(0) Start
PWM(0) end
[GPIO:D]LzGpioDeinit: id 12 is released successfully
​
===========================
PWM(1) Init
[GPIO:D]LzGpioInit: id 13 is initialized successfully
PWM(1) Start
PWM(1) end
[GPIO:D]LzGpioDeinit: id 13 is released successfully
...