Faced with a CNC that took instructions over serial port, and not wanting to deal with ... The hand-made PCB connects via a 3.5 mm headphone jack to DB9 adapter which he describes in another ...

I built this to communicate to an LED sign I bought over ten years ago that still works great but has a traditional DB9 serial port using RS232 communications. This port requires a strict protocol to ...

Build a dongle with a basic DB9 connector and join only pins 2 (Rx) and 3 (Tx) together. Disconnect all serial port connectors from the PC. Connect your dongle alternately to all ports The "control ...