Digital to Analog Converter (DAC) is mostly used to generate analog signals (e.g. sine wave, triangular wave etc.) from digital values.

ARM MBED LPC1768 has a 10-bit DAC in-built with single DAC (analog output) channel.

This DAC can be used to output analog data on the only single pin (p18). This analog output data can vary in the range between VSS and VCC.

The analog output pin p18 of ARM MBED LPC1768 is shown in below image,

ARM MBED DAC Pin

Analog Output or DAC Output:

AnalogOut (pin)

Create an AnalogOut Object first connected to the specified pin.

pin: give the pin name where you want to connect as an input (i.e. p18).

e.g.

AnalogOut sensor_one(p18).

Example

Here is the program to generate sinewave.

Sinewave Generation Program using ARM MBED (LPC1768)

#include "mbed.h"
 
DigitalOut myled(LED1);
AnalogOut Aout(p18);
 
//Note if w_hat is pi/4 this means 8 samples/period. If we measure frequency of this output signal.
//then reconstruction frequency is 8 times this.
//Could put it through a low pass filter to smooth out.
//Also check the offset.
 
//Sine wave reconstruction in this case is much faster(tahn test4_sine) since I calculate the sample values before hand.
//Sine wave period is 2.2*5us = 12us
//Sine wave freq = 83KHz
//Reconstruction freq is 666KHz
 
unsigned short n;
#define pi 3.1415192
#define N 64                  //Numebr of samples in one period 
#define w_hat 2*pi/N          //Normalised radian frequency               
float sine1 [N];              //contains sine wave sample values
 
void init_sine_array(void);
 
int main() {
    init_sine_array();
    n=0;
    while(1) {
        
            Aout = sine1[n];
            n=(n+1)%N;
    }
}
 
void init_sine_array(void)
{
    unsigned short n = 0;
    for (n=0;n<N;n++)
    {
        sine1[n] = 0.5 + 0.5*sin(n*w_hat);   //note the 0.5 V of offset since DAC outputs voltage between 0 and 3.3V
    }
    
 } 

Output Window