This is a firmware, that when uploaded on an atmega328p, or a similar AVR MCU running @16Mhz, enables it to interface with Atmel Studio as if it were an STK500 programmer. In particular, you can use an Arduino to host this firmware. It provides a bridge to program the new attiny817 family of MCUs, that use the UPDI interface, from Atmel Studio, using the STK500v2 protocol:
Atmel Studio -> HW Serial interface -> Programmer MCU (e.g. Mega328P) -> SW Serial on PD6 -> Target MCU (e.g. tiny817)
Currently, I have not tested this software with a level shifter, so the target MCU must run at the same voltage as the programmer.
Vcc Vcc
+-+ +-+
| |
+----------+ +---------------------+ | | +--------------------+
| Atmel | | Programmer +-+ +-+ Target |
| Studio | | | +----------+ | |
| TX +----------+ RX PD6 +------+ 4k7 +---------+ UPDI |
| | | | +----------+ | |
| RX +----------+ TX | | |
| | | | | |
| | | | | |
| | | +--+ +--+ |
+----------+ +---------------------+ | | +--------------------+
STK500v2 +-+ UPDI +-+
Protocol GND Protocol GND
Drawing adapted from: https://github.com/mraardvark/pyupdi
To build, run the make.bat file, after editing it with the path of AVR-GCC on your system. Since this program is meant to talk to Atmel Studio, I provide a makefile suitable for a MS-Windows environment.
There are also pre-built files on the "build" directory. They were built using avr-gcc 8.0 compiled for MinGW by sprintersb: https://sourceforge.net/projects/mobilechessboar/files/avr-gcc%20snapshots%20%28Win32%29/
More information at: http://www.avrfreaks.net/forum/stk500-updi-working-was-enabling-xtiny-updi