In my previous post, things were looking up. I had replaced a couple of faulty chips, re-seated all of the chips on the CPU and Video cards and swapped out the RAM from the CPU card with the expansion cards and now my 380Z was getting to the COS prompt.
All I needed was a key press. Specifically, I needed a ‘B’. Sadly, I don’t have a keyboard.
Looking at one of the technical documents shows that the keyboard interface is a simple 7 bit parallel interface with a strobe. How hard can it be?
Arduino to the rescue?
I had a supply of Arduino pro mini compatible boards and so I set to building an interface and a sketch to drive the circuit. The idea is to catch characters from the ‘duino’s serial port and squirt them out of the parallel port the way the 380Z likes them.
Not so Fast.
I plugged in the board and nothing happened. I restarted the machine and nothing happened again. Just a blank screen, no COS prompt. Doh!!.
I went over the circuit for the interface again and a again and couldn’t find anything wrong with it. It does appear to have toasted the 380Z though.
By coincidence I have just been to the Centre for Computing History in Cambridge and they have a 380Z on a table. I quick word with Jason who runs the place and I have a look inside. Their machine has a different keyboard cable to mine. Mine has an additional connector in-line with the cable. Theirs doesn’t. Sadly, I didn’t take a picture of theirs but it definitely only had one connector at each end.
You can see from the photo here that mine has the additional connector. After that connector, wires go off in the direction of the PSU. I’m wondering if mine has been modified for some reason and that has made it incompatible with my relatively simple interface.
I’ll have to trace where all of the wire go and see if that’s significant. I could also do with confirmation that the keyboard ribbon should be straight through.