Enter TPI (tiny programming interface), and exit all of your previously useful DIY AVR programmers. [Kimio Kosaka] wrote a dual-purpose TPI and ISP firmware for the ATmegaxxUn chips that are used ...

Being a proprietary interface means that even entry-level programmers ... if UDPI AVR support with the Snap is really an afterthought for Microchip. Meanwhile there are also more DIY solutions ...