Ok so this was crazy. I spent 3 hours putting together this usb to serial converter, based on this design: http://www.recursion.jp/avrcdc/cdc-232.html . It is based on an attiny45. It worked first time. But what a mess. Max baud rate is 4800 for this part, but it will do the job. You will see the application in the next post

By the way this blog is moving to www.zethus.ca/ELX. Update your links!

Update: buddy at recursion messed up the serial interrupt edge in the code when using ttl levels. Here is the patch:
Chucks-Mac:tiny45 chuck$ diff uart.h.bad uart.h

61a62,64
> #ifdef UART_INVERT
> #define UART_INTR_CFG_SET (_BV(ISC01)|_BV(ISC00)) /* int on rising edge */
> #else
62a66
> #endif