Replay1 Mainboard
The serial port on the Replay1 is via the 9pin db9 connector at the back left of the board.
See more information here on the wiring diagrams.
https://www.fpgaarcade.com/kb/how-do-i-wire-a-db9-serial-cable-is-it-null-modem/
Replay1 Daughterboard
The serial ports on the Daughterboard are the same ports used as the Daughterboard midi ports comms1 and comms2.
They are located directly behind the Daughterboard CPU socket, near the back of the board.
The pinouts for serial use on the comms1 and comms2 are as follows.
Comms1:
Pin
1 5V
2 Gnd
3 (R|T)X
4 (T|R)X
Comms1:
Pin
1 5V
2 Gnd
3 (R|T)X
4 (T|R)X
Replay2 Coming soon.