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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)
void write (float value)
void write_u16 (unsigned short value)
float read ()
AnalogOutoperator= (float percent)
AnalogOutoperator= (AnalogOut &rhs)
 operator float ()
Protected Member Functions
virtual void lock ()
virtual void unlock ()
Protected Attributes
dac_t _dac
PlatformMutex _mutex

AnalogOut hello, world

/* mbed Example Program
 * Copyright (c) 2006-2015 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "mbed.h"

// Initialize a pins to perform analog and digital output fucntions
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;
            wait(1.0f);
        }
    }
}

AnalogOut example

Create a sine wave.

#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
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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