RS232 Interface

Got a serial communication to PC going with RaspberryPi using a MAX3242-based board.

Raspberry Pi connected to PC via RS232
Raspberry Pi talks to PC via RS232

Motorola lapdock has been really handy to run R-Pi on: the number of cables is minimal and it operates just like a regular notebook.

This is a useful reference to the R-Pi header:

Raspberry Pi header pins layout
Raspberry Pi header

It seems to be difficult to find a good serial software for PC. Are the days of COM ports largely gone? Every time I need it, I have to google it up. This time I've found the one simply called, "Terminal" - this is the link:

On the R-Pi side, first you need to disable getty, and then you can use minicom to talk to its serial port. This is all nicely described on this page:

It is interesting that even though my wire connections were flimsy, I could still get 256000 baud and a solid file transfer! Well, I did use my add-on parallel + serial PCI card on the PC since I needed a parallel port for experimentation, and the controller chip on that card seemed to be quite good.


  • A port closer to the motherboard is COM5
  • R-Pi RXD -> R3OUT (closer to GND) on the MAX board
  • R-Pi TXD -> T3IN (closer to Vcc) on the MAX board
  • The way to quit minicom is to press Ctrl-A Q

This particular MAX board that I had has a 6-pin connector:

1 and 2 are not connected.
3 = GND
4 = R3OUT (Receive)
5 = T3IN (Transmit)
6 = Vcc

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