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AnalogOut

Use the AnalogOut interface to set the output voltage of an analog output pin specified as a percentage or as an unsigned short. Mbed OS provides separate APIs to use percentage or range. Mbed OS supports a maximum resolution VCC/65,536 V, though the actual resolution depends on the hardware.

Note: Not all pins are capable of being AnalogOut, so check the pinmap for your board.

AnalogOut class reference

Public Member Functions
 AnalogOut (PinName pin)
 Create an AnalogOut connected to the specified pin. More...
 AnalogOut (const PinMap &&)=delete
 Create an AnalogOut connected to the specified pin. More...
void write (float value)
 Set the output voltage, specified as a percentage (float) More...
void write_u16 (unsigned short value)
 Set the output voltage, represented as an unsigned short in the range [0x0, 0xFFFF]. More...
float read ()
 Return the current output voltage setting, measured as a percentage (float) More...
AnalogOutoperator= (float percent)
 An operator shorthand for write() More...
AnalogOutoperator= (AnalogOut &rhs)
 An operator shorthand for write() More...
 operator float ()
 An operator shorthand for read() More...
virtual ~AnalogOut ()

AnalogOut hello, world

/*
 * Copyright (c) 2017-2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0
 */

#include "mbed.h"

// Initialize a pins to perform analog and digital output functions
// Adjust analog output pin name to your board spec.
AnalogOut  aout(A5);
DigitalOut dout(LED1);

int main(void)
{
    while (1) {
        // change the voltage on the digital output pin by 0.1 * VCC
        //  and print what the measured voltage should be (assuming VCC = 3.3v)
        for (float i = 0.0f; i < 1.0f; i += 0.1f) {
            aout = i;
            printf("aout = %1.2f volts\n", aout.read() * 3.3f);
            // turn on the led if the voltage is greater than 0.5f * VCC
            dout = (aout > 0.5f) ? 1 : 0;
            ThisThread::sleep_for(1000);
        }
    }
}

AnalogOut example

Create a sine wave.

/*
 * Copyright (c) 2017-2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0
 */

#include "mbed.h"

const double pi = 3.141592653589793238462;
const double amplitude = 0.5f;
const double offset = 65535 / 2;

// The sinewave is created on this pin
// Adjust analog output pin name to your board spec.
AnalogOut aout(A5);

int main()
{
    double rads = 0.0;
    uint16_t sample = 0;

    while (1) {
        // sinewave output
        for (int i = 0; i < 360; i++) {
            rads = (pi * i) / 180.0f;
            sample = (uint16_t)(amplitude * (offset * (cos(rads + pi))) + offset);
            aout.write_u16(sample);
        }
    }
}

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