aio.h File Reference

API Description

AIO is the anlog input & output interface to libmraa. It is used to read or set the voltage applied to an AIO pin.

    /* initialize AIO */
    aio = mraa_aio_init(AIO_PORT);
    if (aio == NULL) {
        fprintf(stderr, "Failed to initialize AIO\n");
        mraa_deinit();
        return EXIT_FAILURE;
    }

    while (flag) {
        value = mraa_aio_read(aio);
        float_value = mraa_aio_read_float(aio);
        fprintf(stdout, "ADC A0 read %X - %d\n", value, value);
        fprintf(stdout, "ADC A0 read float - %.5f\n", float_value);
    }

    /* close AIO */
    status = mraa_aio_close(aio);
    if (status != MRAA_SUCCESS) {
        goto err_exit;
    }

Go to the source code of this file.

Functions
mraa_aio_context	mraa_aio_init (unsigned int pin)
int	mraa_aio_read (mraa_aio_context dev)
float	mraa_aio_read_float (mraa_aio_context dev)
mraa_result_t	mraa_aio_close (mraa_aio_context dev)
mraa_result_t	mraa_aio_set_bit (mraa_aio_context dev, int bits)
int	mraa_aio_get_bit (mraa_aio_context dev)

Typedefs
typedef struct _aio *	mraa_aio_context

Function Documentation

mraa_aio_context mraa_aio_init

(

unsigned int

pin

)

Initialise an Analog input device, connected to the specified pin. Aio pins are always 0 indexed reguardless of their position. Check your board mapping for details. An arduino style layout will have A0 as pin14 but AIO0.

Parameters

pin	Channel number to read ADC inputs

Returns

aio context or NULL

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int mraa_aio_read

(

mraa_aio_context

dev

)

Read the input voltage. By default mraa will shift the raw value up or down to a 10 bit value.

Parameters

dev	The AIO context

Returns

The current input voltage or -1 for error

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float mraa_aio_read_float

(

mraa_aio_context

dev

)

Read the input voltage and return it as a normalized float (0.0f-1.0f).

Parameters

dev	The AIO context

Returns

The current input voltage as a normalized float (0.0f-1.0f), error will be signaled by -1.0f

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mraa_result_t mraa_aio_close

(

mraa_aio_context

dev

)

Close the analog input context, this will free the memory for the context

Parameters

dev	The AIO context

Returns

Result of operation

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mraa_result_t mraa_aio_set_bit	(	mraa_aio_context	dev,
		int	bits
	)

Set the bit value which mraa will shift the raw reading from the ADC to. I.e. 10bits

Parameters

dev	the analog input context
bits	the bits the return from read should be i.e 10

Returns

mraa result type

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int mraa_aio_get_bit

(

mraa_aio_context

dev

)

Gets the bit value mraa is shifting the analog read to.

Parameters

dev	the analog input context

Returns

bit value mraa is set return from the read function

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Typedef Documentation

typedef struct _aio* mraa_aio_context

Opaque pointer definition to the internal struct _aio. This context refers to one single AIO pin on the board.

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