I've been playing with this for a while and it's been a bit flaky so I decided to do some testing on what bit rates work for both the 2 wire mode and 1 wire mode. I tested on two different sets of target hardware and two completely different Serial level converters. Processor is a tiny48. Same results.
With the internal 8MHz oscillator as a clock and the CLKDIV8 fuse set to achieve a 1MHz CPU clock, the fastest reliable bit rates I can run are:
1 wire: 300 bps
2 wire: 2400 bps
The 2 wire limit seems somewhat reasonable. I was expecting the 1 wire mode to do a little better.
Anyone have better results that this? I really wanted to use the 1 wire mode so I can reprogram using only GND, VCC, and DATA, but 300bps is very slow even for a device with only 4K of FLASH.
I am wondering if any serial port settings or use of a USB to serial adapter might be affecting things.
Appreciate any comments.