0

Can the flat cable through which the internal keyboard in the laptop is connected transmit PS/2 or USB signals? Or does it send some other signals like serial or parallel, which are then converted on the motherboard to PS/2 or USB signals using a converter?

another.unix.hacker
  • 1
  • 1
  • 1
    Why should the keyboard signal be converted to any particular format? – Andy aka Jan 18 '23 at 19:43
  • @Andyaka External keyboards usually use USB or PS/2 interfaces, protocols and signals. So there must be some good enough reason for it? – another.unix.hacker Jan 18 '23 at 19:49
  • 1
    It depends on which keyboard it is. We can't know what keyboard you mean and how it works. – Justme Jan 18 '23 at 19:56
  • 1
    it's probably a mechanical switch matrix – jsotola Jan 18 '23 at 20:07
  • 1
    External keyboards need a protocol & electrical interface to get the signals from over 100 keys into the PC using (far) fewer than 100 wires. Even a 10 x 11 matrix would require 21 signals, which would be wildly impractical for a keyboard cable. Internal keyboards have very short (2-3") FFC connecting the keyboard matrix directly to whatever handles it in the laptop. – brhans Jan 18 '23 at 21:37

1 Answers1

2

What signals does the flat cable send in laptops?

From what I have read, the keyboard in a typical laptop doesn't really create signals. It is typically a switch matrix that connects a pair of wires when you press a key. It relies on the circuitry at the other end of the cable to apply power to wires in sequence and measure voltages appearing on other wires.

There is no need for any conversion to USB, PS/2 or older keyboard signalling protocols.

RedGrittyBrick
  • 14,710
  • 5
  • 39
  • 80