Dongles to Fake Presence of a Keyboard?

An anonymous reader asks: "I have a Compaq IPAQ desktop system (legacy free) that will not boot headless. (Yes I did try to tell the BIOS to not generate a no keyboard error, but there is no such setting for the BIOS of this system.) Since I would like to use it such and don't wish to waste a keyboard just to keep it from complaining, I'd like to come up with a small dongle that would fake the system into thinking that there is a keyboard attached. This is the same basic thing that KVM's do, so the circuit shouldn't be that difficult to find. Has anyone heard of such a thing? Can anyone provide or point to somewhere where I can find the basic circuit for this?" How hard would it be to take the connector part from a old non-working keyboard and wiring something like this up?

Comments

Not terribly helpful, but ...

[iMMersE]

I can't imagine such a dongle could be cheaper than picking up a really cheap and nasty keyboard. Here in the UK, you can regularly get keyboards for 2GBP at computer fairs.

You'll also have the added advantage of having a keyboard attached to machine, just in case.

Standard answer: Google/Froogle

[DrFatal]

Keyboard Emulator @ Froogle

Simple Circuit

[Ratbert42]

I've had this bit of text sitting around for years but never bothered to try it (bought some KVMs instead). Buyer beware.

• Most systems detect a keyboard connection by monitoring the current flow through the connector. To trick it, simple wire a 10K ohm resistor between GND (pin 4) and +5V (pin 5). This is on a standard PC/AT style connector (the larger 5 pin one). If you have a PS/2 keyboard, you can either use an adapter to change it to an AT connector, or use the resistor between pins 3 and 4 of the PS/2 adapter. Note that the pinout isn't simply clockwise or counter clockwise:

• PC/AT:
  n
  1 3
  4 5
  2
  
  PS/2:
  n
  5 6
  3 4
  1 2

  as viewed looking into the connector on the keyboard, not the PC. where 'n' is the notch in the shield.