UNO form factor may be "inconvenient" but a lot of shield is designed to fit UNO (and MEGA), I would need a Nano to UNO adapter to use the shield so might as well go straight to "inconvenient" UNO form factor. EDIT Nano can only have TQFP which would require desoldering to replace if I blow it. UNO can have 38 PDIP socket for quick chip swap. And onboard 5v regulator from external power source.
Pin 9, 10, 11, 12, 14, and 15 on CH340g seems to be unused in the 2 schematics above (one has 4 pin header connected to 9-12). For external serial connection maybe? Most of the clones I've seen with CH340g chip don't have 4 pin header so I'll skip them.
I did notice 2 differences in the schematics. The one 6v6gt posted has RX LED coming from TX pin on CH340 to RX pin on ATmega, and TX LED on RX pin to TX pin. But other schematic has RX and TX LED reversed. I don't think it really matters, both usually flashes too fast to tell which line has activity anyway.
Nonetheless I got the schematic and board finished. I've sent the board to a cheap PCB fab for a prototype test to see if I missed anything. If there's no error I will send it to OSHPark for the After Dark special: Black background with shiny copper trace under clear mask. I've seen clones in many color (except all yellow or purple?) and black with clear mask would be a cool looking board.
