Spurred on by the recent interest in my PC keyboard interface, I've more-or-less finished a PCB for it this weekend - hopefully I will get the chance to make it next weekend. I could do with some advice first, however.
The interface I've got is designed to be internal - that is it needs soldering inside the SAM. The reason I went for this option is that it only needs about half the number of chips as an external version, a smaller PCB, and it seemed a nice and neat solution - it doesn't require a precious spare expansion slot. However, it means that a bit of soldering is needed - there is one 9-way ribbon cable and one 8-way ribbon cable that need soldering to the SAM's motherboard keyboard connectors. On mine I have soldered the wires onto the pins on the underside of the motherboard, which was a bit fiddly but works fine - it also means that I can still plug in and use the SAM keyboard. The alternative is to desolder the black connectors into which the membrane pushes and solder the ribbon cables directly into the holes, but now the original SAM keyboard will be inoperable. The third possibility (but no promises on this one) is that I may be able to get some thin pcb which I can solder onto the ribbon cable so that all you have to do is push it into the existing keyboard connectors, much like you do with the membrane. Again, the existing SAM keyboard will be unusable unless I can get hold of some of those 8 and 9-way keyboard connectors to make through connections. There will still be four wires to solder onto the mainboard, however (+5v, 0v, NMI and RESET --- ctrl+alt+break will give a de-bounced NMI and ctrl+alt+del will give a reset). Basically, then, what I want to know is: is this all too much hassle? I can do the external interface if it is, but you'll have to wait a while for it. As for posting the schematic, I'm afraid I can't do that just yet - not least because I don't actually have one! The thing has sort of evolved on stripboard. Also, the circuit isn't fixed - basically I have a number of things I can move around in order to simplify the pcb, so I can't really post a schematic until after I've finished the pcb design. (The software for the microcontroller needs modifying according to the final pcb layout). I hope to have more news soon - please let me know how much hassle you would be prepared to go to to install this thing - do you mind losing the use of your [part-dead?] SAM keyboard? Thanks, Andy
