working with pwm

Working with GPIO

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Examples

• Code example, working with PWM and LEDs
• Code example, working with PWM and LEDs and PWM MikroE BUZZ Click

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Functions

bool dx_pwmSetDutyCycle(DX_PWM_BINDING *pwmBinding, uint32_t hertz, uint32_t dutyCyclePercentage);
bool dx_pwmStop(DX_PWM_BINDING *pwmBinding);
bool dx_pwmOpen(DX_PWM_BINDING *pwmBinding);
void dx_pwmSetOpen(DX_PWM_BINDING **pwmSet, size_t pwmSetCount);

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Structures

PWM binding structure.

typedef struct DX_PWM_CONTROLLER
{
    int fd;
    PWM_ControllerId controllerId;
    bool initialized;
    char *name;
} DX_PWM_CONTROLLER;

typedef struct DX_PWM_BINDING
{
    DX_PWM_CONTROLLER *pwmController;
    PWM_ChannelId channelId;
    PwmPolarity pwmPolarity;
    char *name;
} DX_PWM_BINDING;

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Usage

The following example declares a PWM controller and three PWM LEDs that use the same PWM Controller.

static DX_PWM_CONTROLLER pwm_led_controller = {.controllerId = PWM_LED_CONTROLLER,
                                               .name = "PWM Click Controller"};

static DX_PWM_BINDING pwm_red_led = {.pwmController = &pwm_led_controller, .channelId = 0, .name = "led"};
static DX_PWM_BINDING pwm_green_led = {.pwmController = &pwm_led_controller, .channelId = 1, .name = "green led"};
static DX_PWM_BINDING pwm_blue_led = {.pwmController = &pwm_led_controller, .channelId = 2, .name = "blue led"};
static DX_PWM_BINDING pwm_user_led = {.pwmController = &pwm_led_controller, .channelId = 3, .name = "user led on Seeed Mini"};

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Initializing a set of PWM peripherals

For convenance you can declare a set of PWM peripherals and use the set based functions to open. Add each PWM peripheral by reference to the set (array) of PWM peripherals.

static DX_PWM_BINDING *pwm_bindings[] = {&pwm_red_led, &pwm_green_led, &pwm_blue_led, &pwm_user_led};

In main.c, open the set of PWMs using the dx_pwmSetOpen function.

static void InitPeripheralsAndHandlers(void)
{
    dx_pwmSetOpen(pwm_bindings, NELEMS(pwm_bindings));
    dx_timerSetStart(timerSet, NELEMS(timerSet));
    ...
}

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Set the PWM duty cycle and the LED brightness from a periodic timer event

/// <summary>
/// Simple PWM example - 1kHz (1000 Hz), and alter duty cycle
/// </summary>
static void update_led_pwm_handler(EventLoopTimer *eventLoopTimer)
{
    if (ConsumeEventLoopTimerEvent(eventLoopTimer) != 0) {
        dx_terminate(DX_ExitCode_ConsumeEventLoopTimeEvent);
        return;
    }

#ifdef OEM_SEEED_STUDIO_MINI
    // NO RGB LED so set PWM on the user LED
    static DX_PWM_BINDING *pwmLed = &pwm_user_led;
#else
    static DX_PWM_BINDING *pwmLed = &pwm_red_led;
#endif

    static int duty_cycle = 0;

    switch (duty_cycle % 4) {
    case 0:
        dx_pwmSetDutyCycle(pwmLed, 1000, 100);
        break;
    case 1:
        dx_pwmSetDutyCycle(pwmLed, 1000, 80);
        break;
    case 2:
        dx_pwmSetDutyCycle(pwmLed, 1000, 40);
        break;
    case 3:
        dx_pwmSetDutyCycle(pwmLed, 1000, 0);
        break;
    default:
        break;
    }

    duty_cycle++;
}