Atmel Xmega USB/Serial Arbitrary Waveform Generator

This instructable walks you through programming and using the Boston Android Xmega evaluation board to work as a simple arbitrary waveform generator taking advantage of the integrated 12bit DAC and high speed DMA controller. I have provided precompiled firmware as well as source code which can be loaded onto the device and configured via a USB port on your PC or laptop.

You will need a computer (mac, pc, linux all supported) with an available USB port, free driver for the USB-Serial adapter, a Boston Android Xmega EVAL-USB-64 development board ($31.99) and an open source AVR chip programming utility called AVRDUDE.

Once set up, you can generate sine, ramp, triangle, square or any waveform you define from 5 to 20KHz with amplitude of up to 3.3Vp-p. It is possible to generate faster waveforms with the arbitrary waveform feature (up to 500KHz).

Step 1 What you need

1) Boston Android Xmega EVAL-USB-64 (or comparable) Development Board
2) PC with USB port
3) AVRDUDE (free AVR programing software)

Also recommended:

Oscilloscope (to view waveforms)
Headphone or small speaker (to listen to waveforms)
WINAVR and AVRSTUDIO to modify the source code and built your own version of the waveform generator software

Although this example walks through programming and using the EVAL-USB-64 board, you can use any of the EVAL-USB boards from Boston Android. And if you're very experienced you can download the example source code and build for other target hardware such as the Atmel XPLAIN evaluation board, or the Xmega boards available from chips45 and Mattair, Megavore. The xmega family allows effortless migration of code from one chip to another.

Comments

[kosmo!!]

Is it possible to use the code for an Xmega128A1?

[wandererwolf]

Atmel worked very hard to make all the Xmega chips in the family derivatives of the Xmega128A1. So for example an Xmega128A3 just has fewer pins and fewer peripherals, but the ones it does have reside at the same addresses as the bigger Xmega128A1 chip. They also arranged memory at the same start addresses regardless of memory size. In theory all this means binary compatibility between chips (as long as the peripherals are available), so you MIGHT be able to load compiled code for the Xmega64A3 on to an Xmega128A1 and have it work, but there may be some catch. Certainly worth a try!

[kosmo!!]

Ok, thanks for fast support. But I have an another question. Im using an STK600 board and I have no serial terminal. Which parameters can change the frequency? I need 20 khz sinewave.

[gustep12]

Very nice, thank you. Do you think it would be possible to extend this design to use an external 16-bit DAC, like the TI DAC8830, for improved 16bit resolution and better drift stability? Most DACs use SPI as the interface, what would it take to hook these up?

[wandererwolf]

There are several dedicated SPI interfaces on the Xmega chip you could use to interface with an external DAC. You can also configure the USARTS on every port to master SPI mode.

If you need more help let me know.

[catxld]

how would I boost the voltage amplitude of the frequency from 3V to 20V? if it uses opamps then what opamps would be best for boosting voltage which would cover all or most of its frequency ranges from 1hz ~ 500khz?

[wandererwolf]

You could definitely use an opamp amplifier circuit to boost the output voltage to 20V over that frequency range. The only limit of an opamp is that it generally is only used for low current applications. For example you wouldn't use an opamp circuit to generate a signal to drive a motor, etc.

If you do a web search there are lots of example opamp circuits to choose from. I would breadboard them and try them out.

Best of luck!

[wandererwolf]

The output of the Xmega DAC can generate 0-3.3V and a few mA of current. To get higher voltage you will need (as you suggest) an opamp (low current only) or a linear amplifier circuit capable of driving your load.

What are you attempting to drive up to 20V? Is it a speaker? Any requirements for efficiency? Do you have a 20V supply to drive the output?

[catxld]

Basically I would be using it for all kinds of experiments, speaker, radio,EM , even experimental motor. but id be using the arbitrary waveform feature in most of these experiments, im wondering what is the range of the arbitrary function is it 140hz to 500KHz?

[wandererwolf]

In theory the DAC can run up to 2MHz, but the example code here can only reach about 100KHz. For 500KHz you will be limited to square waves and need to write your own code to drive the DAC that fast.

As for the output stage going up to 20V you should do a search for linear amplifiers. You could probably just use an Audio Amplifier circuit. They have some at http://www.sparkfun.com/ which can boost the signal output from this board to the power levels you're talking about. I've used an amplifier off ebay (search for TA2024 amplifier about $9) to generate high frequency signals to drive a small speaker. Don't ask why. ;-)

[bhudz062289]

how can i program the at89s52,,can you help

[wandererwolf]

This instructable is specific to the Atmel Xmega microcontroller which includes an integrated DAC. I believe if you search you can find examples of waveform generation on an Atmel 8bit microcontroller such as the at89s52 using a resistor ladder.

[whstark]

I loaded C program seems to be missing h file got 37 errors and 19 warnings. Can you help.

[wandererwolf]

The only header files included in xmega-waveform-serial.c are provided by WinAVR/AVR-GCC. Could it be AVRStudio (or whatever build environment you are using) is having trouble finding the path to the header files? Usually, the compiler will tell you if it can't find a particular header file. If you email me your AVRStudio project file, I will check if everything is setup correctly.

[kgkitchen]

I found it necessary to tweak the baud rate in order to get reliable communication with hyperterminal  - Here's the code. 


// 9600 @ 32Mhz as calculated from ProtoTalk Calc
// see web page at: http://prototalk.net/forums/showthread.php?t=188

 USARTF0.CTRLC = USART_CHSIZE_8BIT_gc | USART_PMODE_DISABLED_gc;

int bsel = 3317;
uint8_t bscale = 12;

USARTF0.BAUDCTRLA = (uint8_t) bsel;
USARTF0.BAUDCTRLB = (bscale << 4) | (bsel >> 8);
 

[ganzziani]

Cool Stuff, also check out my own XMEGA oscilloscope, arbitrary waveform generator and calculator: Xmegalab
http://www.gabotronics.com/development-boards/avr-xmegalab.htm

[slick8086]

How do I do this on OS X 10.5.8?

[wandererwolf]

I haven't tried this on a Mac, but as long as you have AVRDUDE installed you should be able to load the code over the serial port using the OSX commandline and then use whatever terminal program you have handy to open a terminal connection over the serial port to the board. I'm not sure how OSX names serial ports (in windows and linux they are COM1 COM2, etc) When you get it working post any tips or tricks you used. :-)

[slick8086]

So I tried this on my mac first and I thought that my terminal program wasn't working... So I tried it on a winxp box with hyperterm and I'm getting the same issue. When I connect to the device and type 'h' an 'o' shows up and pressing enter gives me a 'm'. I wrote the program to the device with AVRDUDE on my mac and I didn't get any errors. What could be my problem?

[slick8086]

Woohoo got it working with the new hex file:
http://www.bostonandroid.com/binaries/xmega-waveform-serial2.hex

When I tried uploading with avrdude on my mac I got:

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
               0x0c != 0xff
avrdude: verification error; content mismatch
avrdude done. Thank you.

but using avrdude in win xp worked.
I was able to connect and control with my mac though using screen:

sexybeast:avrdude aaron$ screen /dev/tty.usbserial-A800cAoo 9600

[mathman47]

Nice job.  I just studied waveforms as part of my Amateur Extra class Ham license.  Now I can make them.  Like the evaluation board.  I was unaware of this source.  Thaks.

[wandererwolf]

I believe the Arduino family is based entirely on Atmel ATmega chips which do not include a DAC. One of the nice features of the XMega family is that Atmel finally put a DAC on an 8bit micro. I wouldn't be surprised though if someone is already working on porting the Arduino environment to XMega for future boards.

[fagnelli]

Really nice.  I was just wondering whether you could use an Arduino for that.  Thanks for sharing.

[marc.cryan]

Nice - Make an Empire State building waveform!!

[wandererwolf]

To generate the elusive Empire state building waveform execute the following command:

w 1000 20 0 0 0 0 0 800 3000 3300 3400 4095 3400 3300 3000 800 0 0 0 0 0 0

pic

[marc.cryan]

Awesomeness knows no bounds!!