UFE A1200 Keyboard Daughterboard Design
Posted by retromaster on July 28, 2010
After the initial release of information on UFE, quite a few people asked about A1200 support. So, here is the early result of my design efforts for an UFE A1200 keyboard daughterboard.
The board is designed to plug into the keyboard flex cable socket on the A1200 motherboard (see the edge connector on the bottom of the PCB). The flex cable from the keyboard goes into the connector on the top left side of the board. So, this board acts as a kind of pass-through.
A 40-pin PIC MCU sits on the right side and is responsible for scanning the keyboard and translating keycodes into the I2C protocol for UFE communication. A couple of 74ls245 chips are placed in between the keyboard and motherboard connectors. These are used to disable the column drivers on the Amiga side when UFE takes over control of the keyboard. This way UFE can scan the keyboard without interference from the Amiga keyboard MCU.
This should all work in theory, based on my understanding of the A1200 schematics and the reverse-engineered A1200 keyboard schematics. Of course, there is a decent chance it could fail, so that’s why there are no schematics accompanying this post. I’ll build the PCB soon and write the firmware for the PIC and see if it actually works🙂. I haven’t checked the A600 schematics yet, but there is a good chance that this will also work with the A600 without modification.
Part of the challenge here was to make everything fit in the rather limited space. That’s why the board ended up being double-sided. It does not require plated-through holes, however, and there are only a few vias that can easily be handled by soldering wires on both sides. These measures should help keep the cost to a minimum. The current board layout also requires the A1200 metal shield to be removed, but this may perhaps be avoided, by elongating the board even further.