| ??? 01/31/08 07:52 Read: times |
#150099 - de-spiking inputs Responding to: ???'s previous message |
Richard Erlacher said:
Debouncing? I'd have thought that the 8042 or whatever takes its place handles that, as it's not possible for it to produce an unambiguous output if it doesn't properly debounce the scan. OK it's not 8042, that was/is on the PC side... If there was ever an intel microcontroller in the AT keyboard (there might have been in the original PC keyboard, maybe an 8048), which I doubt (by that time there were undoubtedly much cheaper microcontrollers available for that purpose), it certainly did debounce the key matrix input itself. However, for a real-world application, the prudent engineer rarely lets an input coming into the box from outside, especially from a not-so-well-defined-electrically output as the keyboard is, debounced - or, read it "de-spiked", if you want. --- Btw. your remark reminded me that this might be one of the simplest solutions of your problem - pick an 8042 from any old PC motherboard, wire it up onto the bus of the host processor, and you're done. It does not spit out the scancode, you need to ask for it; but it's a simple read from a memory (or I/O if it's a separate address space) position. Jan |
