At 03:17 PM 5/29/00 -0700, you wrote: >My guess: You have a short in there somewhere. That's an OC or OD >(open collector or open drain) driver, should never be held low like >that... Pulled low sometimes when toggling the clock line, yes, but not >always. Your pull-up resistor's tested good, I assume > >Cycling power should cause some activity from the keyboard (LED's should >flash and a little more) - NEVER should data be held low, as then the >host computer cannot talk TO the keyboard. Something's wrong. > > Mark I have two keyboards that are behaving like this. Both work well when hooked to a PC. One sticks the data line low, the other sticks it high. The first one has all LED's stuck on, the second has them blinking. A third keyboard, which I tried after the original post, seems to work fine with exactly the same test set-up. That is, on this third board I get pulses on the scope for both data and clock lines when I push a key. Yet all three keyboards work fine when hooked to a PC. Clearly the two that don't work are older than the one that does, because they have the older style din plug. For the newer keyboard I'm using a minidin to din adapter. I'm wondering if there wasn't some sort of reset procedure required on these older keyboards. At least I now have one that's working that I can experiment with. John Hansen