Dangerous Prototypes Open Source Hardware

Re: Bus Pirate AVR port?

Reply #15 – June 11, 2010, 12:12:58 pm

Progress continues...

http://blog.hodgepig.org/articles/000037-bn1/index.html

It's a bit different to the Bus Pirate, but works similarly.

The AVR is running at 5V (it does have optional internal 3.3V regulator, but it can only supply 50mA and at 3.3V the clock speed must be <= 8MHz).
So, I'm using two bus switches for a full 8 bit port.

The external 3.3V regulator is software controlled. But, the 5V line just comes straight from USB.

Re: Bus Pirate AVR port?

Reply #16 – June 11, 2010, 02:44:03 pm

[quote author="jrt"]The AVR is running at 5V (it does have optional internal 3.3V regulator, but it can only supply 50mA and at 3.3V the clock speed must be <= 8MHz).

The external 3.3V regulator is software controlled. But, the 5V line just comes straight from USB.
[/quote]Careful, if you want to run at the full 16 MHz, then you'll need more than straight USB voltage.  The AT90USB162 does not reach 16 MHz until the voltage is 4.5V, and yet USB allows the voltage to drop as low as 4.0V.  Admittedly, that is the worst case, with your board plugged into an unpowered hub, but it's still perfectly legal for you to get as little as 4.0V, and then the AVR won't run more than about 12 MHz (rough estimate from the graph in the data sheet).

For best results, I recommend the Maxim MAX1595 or similar. With just a few capacitors, it generates a full 5.0V from anything down to 1.8V, so you're prepared for anything that USB might provide.  If you need more current, Maxim has other chips up to double the power.

Re: Bus Pirate AVR port?

Reply #17 – June 23, 2010, 07:16:34 pm

There is a pretty similar project to Bus-Pirate and thats "USBProg" ( http://www.embedded-projects.net/index.php?page_id=165 ) by Benedikt Sauter. Its also open source and allows to use several different kind of features to utilize the little AVR.

I bought one some month ago, but switched to Bus-Pirate because I wanted to play with something new ;-)

If you really want to work on a bus-pirate similar device, but it needs to be AVR based, this could be the right project for you. At the end it could be a win-win situation for both projects are the devs still can learn from each other.

Daniel

Re: Bus Pirate AVR port?

Reply #18 – September 10, 2010, 10:09:16 am

Just to round off this thread...

I did get this finished, it's here:
http://blog.hodgepig.org/busninja/ (for Arduino and USB AVRs)

http://blog.hodgepig.org/articles/000048-spi/index.html (just the SPI part implemented on MSP430 for the TI Launchpad board)

Re: Bus Pirate AVR port?

Reply #19 – September 10, 2010, 10:31:03 am

Cool! Great writeup too.