Remapping the HP150 keyboard

I beg to differ... Firstly, as I metnioned several times in earlier messages in this thread, the HP120 and HP150 keyboards use 4000-series CMOS logic chips running at 12V. AFAIK the BASIC Stamp and PICAXE run at esentially TTL levels. So I'd need level shifters -- 2 stages on the inputs (clock and reset lines multiplexer in the keyboard). That accounted for 3 of the 5 chips in my modification board (a 4050 for the inputs and a couple of 74LS07s for the outputs). You could get away with resistors and clamp diodes for the former, I suppose, but ithat's not a big space saving. Secondly, neither of us know, I believe, tehe exact timing of the HP1x0 keyboard interface. It's all controlled by an 8041 in the machine. There's a clock line output from that which steps the scan counter in the keyboard on to the next key, some time after that the 8041 looks at one of its Test inputs to see if that key is pressed. But I don't know what 'some time' is. So I don't know how long I can spend working out what value to send to the decoder/multiplexer. Last time I looked at the BASIC Stamp, you wrote the program on a PC and compiled it to a pseudocode that was downloaded to the Stamp and interpretted there. I have no idea of the performance of that, the documetnation that was available didn't seem to go to a low enough level to work it out. And of course for me to use the Stamp, I'd have to get some machine to run that pseudocode compiler on. Which I don't have. So lets see... _apart from the level shifters_, my solution is 2 chips. One 14 pin (4024 counter), the other 28 bit (27C64 EPROM). I could have got that into a 24 pin package (2716), but the 27C64 is easier to find. That provides a solution where I cna work out the timing performance, and where I don't need any closed software to build it (I worked out the EPROM contents by hand using pen and paper in about half an hour, I would have had to work out much the same thing no matter what solution I adopted I am not against microcontrollers, but I really can't see they make any sense here at all. And there's another thing. I wanted to be able to go back to the Hp150 layout easily. Of course this just means a second table in the EPROM or microcontroller, with a _switch_ to select between them. And that switch has to be mounted soemwhere, which presumably means making holes in the keybosard casing. No, I am not going to consider using a reed switch and a loose magnet, the last thing I need near floppy disks is a loose magnet. Anyway, it's somewhat academic now. I have mounted it all up. The modifications to the HP case consist of cutting away part of the internal back ridge of the top case (to route the ribbon cable through), a similar cut/file to the clip-on cable cover and 4 holes in the top. The switch I mentioned is, of course, mounted on the box bolted ot the top of the keyboar containing my modification board. -tony