Typically, debugging via the serial monitor and burning the bootloader requires 2 connectors for a bare ATtiny3217 and others:
FTDI and UPDI (like the ICSP connector for the Atmega328)
These connectors, however, take up a lot of space on the pcb, especially with respect to the fact that the ATtiny devices, such as the ATtiny3217, are very small. That is why I have designed a new combined FTDI / UPDI connector, which take less space on the pcb. See the old and new situation:
[the reset] capacitor belongs, just like the UART IC, to the FTDI adapter side.
I'm not sure I agree with that, but it's arguable. Since you need an adapter board anyway, I guess its academic...
I find 1.27mm connectors and cables a bit tiny to work with, fragile, and hard to find.
Do you have part numbers and/or links for the connectors you're using? (Hmm. Micro-USB B has 5 conductors. But THAT WOULD BE WRONG!)
The new cheap and powerful Arduino compatible ATtiny AVR XMEGA microcontroller series from 2018 (such as the ATtiny3217) has small packages. But the two required programming connectors FTDI / UPDI in the standard housings are too large in relation to the chip. That's why I came up with a smaller combined FTDI / UPDI connector.
