Since the tiny44 doesn’t have a UART, we could either use the SoftwareSerial library to big-bang serial on any pin, or we could make use of the SPI hardware support provided by the tiny44′s USI module.  The former is prone to timing problems, but is probably easier to setup.  The latter makes sense because the necessary SPI comm pins are the same as that used for ISP programming, and thus are already cabled, and the hardware comm support should reduce the flash and resource usage in the tiny44.  I’ve started down the SPI route and am adding USI SPI support to the BrushBot core that would more or less replicate the functionality of the HardwareSerial code found in the Arduino core.  This will allow “print” statements to work over SPI.

In order to do both the ISP programming and debug comm with a single device, we’ll need to use an Arduino rather than Atmel’s AVRISP.  I picked up a handful of cosmetically defective but fully functional Teensy 2.0‘s at Monday’s DorkBot at a very reduced price that will fit the bill.  If you need an Arduino to use for programming, then see me at Saturday or Monday’s meeting and get one for what I paid for it.

Monty

Also, if you have the smaller BrushBotComm board (w/o the transistors), hold off on installing the 5-pin programming header if it’s not too late already.  It turns out that a 6-pin header can be easily installed with the tail of the extra pin bent over such that it can be soldered to the V+ pin on either the switch or D5.  This will allow the small board to match the pinout of the big board, and allow either board to be powered by the programmer.  I’ll trade your 5-pin connectors for 6-pin connector the next time we meet.

Monty

Update 3/26/2010:
Arduino support code and instructions added here: brushbotcomm-board-software