Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

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.

2 Responses to “UFE A1200 Keyboard Daughterboard Design”

  1. Ralf said

    The UFE is really a great project!

    Why don’t you connect to the data and clock signal of the original keyboard controller of the A1200, similar to the A500 adapter board. This way you can use the same code for both versions, only another way of connecting to the signals is needed. The design could be like the lyra ps/2 keyboard adapter that is plugged on top of the keyboard mcu using a plcc socket.

  2. retromaster said

    Thank you, Ralf!

    The reason why I am doing it this way for the A1200 is that the keyboard daughterboard not only needs to read the keypresses, but it also needs to prevent the Amiga from receiving keypresses when the UFE user interface is active. The A500 daughterboard does this by taking control of the clock line. As far as I can see, this would not be possible to do with only a single connection point to the motherboard. So, this is the best way I’ve been able to come up with so far.

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