nrf52832 PWM外设产生PWM波形笔记

static void demo2(void)
{
    NRF_LOG_INFO("Demo 2");

    /*
     * This demo plays back two concatenated sequences:
     * - Sequence 0: Light intensity is increased in 25 steps during one second.
     * - Sequence 1: LED blinks twice (100 ms off, 100 ms on), then stays off
     *   for 200 ms.
     * The same output is generated on all 4 channels (LED 1 - LED 4).
     * The playback is repeated in a loop.
     */

    enum { // [local constants]
        TOP        = 10000,
        STEP_COUNT = 25
    };

    nrf_drv_pwm_config_t const config0 =
    {
        .output_pins =
        {
            BSP_LED_0 | NRF_DRV_PWM_PIN_INVERTED, // channel 0
            BSP_LED_1 | NRF_DRV_PWM_PIN_INVERTED, // channel 1
            BSP_LED_2 | NRF_DRV_PWM_PIN_INVERTED, // channel 2
            BSP_LED_3 | NRF_DRV_PWM_PIN_INVERTED  // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_500kHz,   //设置PWM外设的时钟
        .count_mode   = NRF_PWM_MODE_UP,    
        .top_value    = TOP,    //PWM波形周期，相当于STM32的ARR值
        .load_mode    = NRF_PWM_LOAD_COMMON, //通道比较值同时加载
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config0, NULL));
    m_used |= USED_PWM(0);

    // This array cannot be allocated on stack (hence "static") and it must
    // be in RAM.
    static nrf_pwm_values_common_t seq0_values[STEP_COUNT];
    uint16_t value = 0;
    uint16_t step  = TOP / STEP_COUNT;
    uint8_t  i;
    for (i = 0; i < STEP_COUNT; ++i)
    {
        value         += step;
        seq0_values[i] = value;
    }

    nrf_pwm_sequence_t const seq0 =
    {
        .values.p_common = seq0_values,
        .length          = NRF_PWM_VALUES_LENGTH(seq0_values),
        .repeats         = 1,    //此PWM值的数组（队列）重复加载的次数为（repeats+1）
        .end_delay       = 0
    };

    // This array cannot be allocated on stack (hence "static") and it must
    // be in RAM (hence no "const", though its content is not changed).
    static nrf_pwm_values_common_t /*const*/ seq1_values[] =
    {
             0,
        0x8000,
             0,
        0x8000,
             0,
             0
    };
    nrf_pwm_sequence_t const seq1 =
    {
        .values.p_common = seq1_values,
        .length          = NRF_PWM_VALUES_LENGTH(seq1_values),
        .repeats         = 4,
        .end_delay       = 0
    };

    (void)nrf_drv_pwm_complex_playback(&m_pwm0, &seq0, &seq1, 1,
                                       NRF_DRV_PWM_FLAG_LOOP);  

//nrf_drv_pwm_comples_playback 函数的意思是：先按seq0的设置模式加载到m_pwm0,然后再加载seq1的设置模式，然后就是循环 （NRF_DRV_PWM_FLAG_LOOP）执行seq0,seq1.
}