There is an odd famine of information about this particular subject available in text form. If you google “usbasp tpi” and things like it, you’ll find posts on the avr forums filled with incorrect information and schematics. This post is an attempt to remedy this.
I intend to show exactly the following, no more and no less:
- What is TPI?
- How to reprogram your usbasp to be capable of TPI.
- How to wire up a TPI-only microcontroller (such as the ATTiny20) to the usbasp’s ISP interface.
- Why you might pick one of these newer devices, rather than sticking with the tried-and-true ISP AVRs.