I have devices with several similar boards, all of which are basic computers (with CPU, RAM and ROMs etc.). They all interface to the I/O unit via a standard connector, although the connectors aren't all wired the same, unfortunately. The I/O unit comprises of a switched mode PSU (+12V +5V -5V), various switches (tied to ground) and 15kHz RGB video.

I would like to use one I/O unit as a test rig, and be able to switch the lines accordingly for each board automatically. I will probably use an Atmel device to keep note of the configurations, as I have several spare.

My main issue is that some of the pins carry voltage. Unfortunately, even these vary from board to board. The PSU is rated at 15A on the +5V line, 3A on the +12V line and 1A on the -5V line, although I'm sure most of the boards don't draw anywhere near that amount of current (I seem to recall 5A being plenty for one board on the +5V line). There are quite a few lines on the connector.

All that I can think of is using relays, but as there are quite a few lines (around 60-70, I believe), that's an awful lot of relays!

Can anyone think of a solution?


They all interface to the I/O unit via a standard connector

If the connector has a ribbon cable, identify the problematic signals and cut or re-route these lines on the cable. If this becomes too much of a rat's nest or you don't have access to the individual signals, you could manufacture a breakout board for each processor board to standardize the connections to your I/O module.

  • \$\begingroup\$ Yes, I've effectively been making breakout boards for each one. It gets a bit tedious when there are hundreds of boards, though! I was hoping for something reusable, but I think it would be huge and expensive, unfortunately! \$\endgroup\$
    – retro
    May 14 '12 at 22:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.