Easy Atmel Xmega Sine Wave / Waveform Generator

This is how you can use one of the BostonAndroid.com Xmega evaluation boards ($20)  to create a simple adjustable sine waveform generator with 12bit resolution and capable of producing frequencies from 125Hz - 20KHz using the integrated DAC. You can modify the code to produce any arbitrary waveform at up to 1MHz on 2 channels. You need only a PC, an eval board and a suitable Atmel programmer (AVRISP is under $30 new).

There are a LOT of features packed into the Xmega microcontrollers. This instructable is meant to demonstrate some of the really powerful ones like a 12bit DAC, 12bit ADC, DMA controller and open source compiler (avr-gcc).

Step 1 What you need

You will need the following to complete this project:

Boston Android Xmega EVAL-01 Development Board ($20) or build your own
Murata PV36W103C01B00 Trimpot 10Kohm, 25turn (or equiv from Mouser)
PC with AVR Studio 4 (free)
AVRISP mkII programmer ($30)

 

Comments

[kosmo!!]

Where i can set the nummer of cycles?

[kosmo!!]

I've forgotten:

Is it possible to realize the two fixed frequenz without potimeter?

[kosmo!!]

would it be possible to modify this so that it could generate two frequencies (20khz and 22khz) ?
For example:

int data[] = {0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1};

for (int i = 0; i< sizeof(data); i++){


if(data[i]==1) "frequency should be 22khz" ;
else " it should be 20 khz;
}


It is possible to add this to the source code and is it possible to adjust the repetitions (loops)?

[gustep12]

Very cool, I like that this instructable is very simple and well-explained. I think I might use this as my first XMega build.

[prakash.mpv]

Congrats friend great work....

[dustin4321]

 Can anybody get the ADC working in 12bit? I think this would be amazing when interfaced by a synth ribbon controller or an ondes martinot type deal. Very cool and minimal synth toy. But it would surely need the increase in resolution. 

great instructable!

[wandererwolf]

You can change the ADC to sample at 12bits by setting CTRLB as follows:

  ADCA.CTRLB = 0x0;        // set 12 bit conversion right adjusted

Then you need to read two separate bytes and put the 12bit value back together.

      tmp = ADCA.CH0RESL;
      tmp += ADCA.CH0RESH<<8;
      sum += tmp;

It's possible the avr-gcc compiler is smart enough to allow you to read the whole 12bit value in one shot like this:

  sum = ADCA.CH0RES;

I tried this and it compiles but I don't have a board handy to confirm it works.

[marc.cryan]

Congrats on the frist X-mega instructable!

[Berserk87]

 Holy crap a true sine wave!

[wandererwolf]

Well, sure, not all that exciting on its own. The fact that it is generated by a digital microcontroller and can be programmed to output any waveform you want at a wide range of frequencies is the nifty part.

[Berserk87]

would it be possible to modify this so that it could take 12VDC and output 120VAC @ 60Hz.?
basically turn it into an efficient inverter.

[wandererwolf]

The regulator is limited to 6VDC input, but you could generate a 60Hz sine wave at 3.3V p-p on the DAC then use a digital line to create a high freq >10MHz PWM signal to drive an inductive flyback transformer to get up to 150V then modulate the signal with a high voltage BJT or FET and generate the 120VAC you want. I don't think it would be good for high current applications, but if you search the internet you will find a number of designs using microcontrollers to generate high voltage sources using flyback configurations.