led.h File Reference

API Description

LED is the Light Emitting Diode interface to libmraa. It is used to access the on board LED's via sysfs.

    /* initialize LED */
    led = mraa_led_init(USER_LED);
    if (led == NULL) {
        fprintf(stderr, "Failed to initialize LED\n");
        mraa_deinit();
        return EXIT_FAILURE;
    }

    /* read maximum brightness */
    val = mraa_led_read_max_brightness(led);
    fprintf(stdout, "maximum brightness value for LED is: %d\n", val);
    if (val >= 1) {
        val = 0;
    } else {
        /* never reached mostly */
        val = 1;
    }

    /* turn LED on/off depending on max_brightness value */
    status = mraa_led_set_brightness(led, val);
    if (status != MRAA_SUCCESS) {
        fprintf(stderr, "unable to set LED brightness\n");
        goto err_exit;
    }

    /* sleep for 5 seconds */
    sleep(5);

    /* set LED trigger to heartbeat */
    status = mraa_led_set_trigger(led, LED_TRIGGER);
    if (status != MRAA_SUCCESS) {
        fprintf(stderr, "unable to set LED trigger to: heartbeat\n");
        goto err_exit;
    }

    fprintf(stdout, "LED trigger set to: heartbeat\n");

    /* close LED */
    mraa_led_close(led);

Go to the source code of this file.

Functions
mraa_led_context	mraa_led_init (int led)
mraa_led_context	mraa_led_init_raw (const char *led_dev)
mraa_result_t	mraa_led_set_brightness (mraa_led_context dev, int value)
int	mraa_led_read_brightness (mraa_led_context dev)
int	mraa_led_read_max_brightness (mraa_led_context dev)
mraa_result_t	mraa_led_set_trigger (mraa_led_context dev, const char *trigger)
mraa_result_t	mraa_led_clear_trigger (mraa_led_context dev)
mraa_result_t	mraa_led_close (mraa_led_context dev)

Typedefs
typedef struct _led *	mraa_led_context

Function Documentation

mraa_led_context mraa_led_init

(

int

led

)

Initialise led_context, based on led index.

Parameters

led	ID of the LED

Returns

LED context or NULL

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mraa_led_context mraa_led_init_raw

(

const char *

led_dev

)

Initialise led_context, based on led function name. The structure of LED entry in sysfs is "devicename:colour:function" This api expects only one unique LED identifier which would be "function" name most often. For instance, mraa_led_init_raw("user4");

Parameters

led_dev

Name of the LED device

Returns

LED context or NULL

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mraa_result_t mraa_led_set_brightness	(	mraa_led_context	dev,
		int	value
	)

Set LED brightness

Parameters

dev	LED context
value	Integer value to write

Returns

Result of operation

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int mraa_led_read_brightness

(

mraa_led_context

dev

)

Read LED brightness

Parameters

dev	LED context

Returns

Brightness value

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int mraa_led_read_max_brightness

(

mraa_led_context

dev

)

Read LED maximum brightness

Parameters

dev	LED context

Returns

Maximum brightness value

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mraa_result_t mraa_led_set_trigger	(	mraa_led_context	dev,
		const char *	trigger
	)

Set LED trigger

Parameters

dev	LED context
trigger	Type of trigger to set

Returns

Result of operation

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mraa_result_t mraa_led_clear_trigger

(

mraa_led_context

dev

)

Clear active LED trigger

Parameters

dev	LED context

Returns

Result of operation

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mraa_result_t mraa_led_close

(

mraa_led_context

dev

)

Close LED file descriptors and free the context memory

Parameters

dev	LED context

Returns

Result of operation

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Typedef Documentation

typedef struct _led* mraa_led_context

Opaque pointer definition to the internal struct _led

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