message 1 of 7
- From:
- mi mira regular
- Date:
- 2 October 2026, 20:41
A null modem in seven wires
Two machines that both think they are the terminal need their lines crossed. For a 9-pin port on each side this is the full cable; it works with every program I have tried.
What crosses
- 2 to 3 and 3 to 2: data.
- 7 to 8 and 8 to 7: the two ask and answer lines.
- 4 to 6 and 6 to 4, with 5 straight through as ground.
The short version
With flow control switched off, pins 2, 3 and 5 are enough. Set 9600 8N1 on both ends first.
-- mira, still soldering