9 pin serial mouse question

June 8, 2005 2:16 PM

"There's a 9 pin serial mouse cable. I have orange, blue, green and white wires. Which is ground?"
posted by nthdegx to technology (10 comments total)

Pin 5 on a D9 serial connector should be ground. If you need to figure out which loose wire on the other end corresponds to pin 5, just probe it with a multimeter.
posted by mr_roboto at 2:23 PM on June 8, 2005

RS-232 pin layout.
posted by AlexReynolds at 2:25 PM on June 8, 2005

Yes, I was able to find that too. In lieu of multimeter, which colour is ground?
posted by nthdegx at 2:26 PM on June 8, 2005

Green's a pretty typical color for ground, but I have no idea whether it's the right color in this case.
posted by box at 2:40 PM on June 8, 2005

So according to this, quite some way down it says...

For 9-Pin to 9-Pin device, simply wire straight through

9-Pin
PC/AT Device
------ ------
1 DCD RTS 1-1 Blue-Blue
2 RX TX 2-2 Orange-Orange
3 TX RX 3-3 Black-Black
4 DTR DSR 4-4 Red-Red
5 GND GND 5-5 Green-Green
6 DSR DTR 6-6 Yellow-Yellow
7 RTS CTS 7-7 Brown-Brown
8 CTS DTR? 8-8 White-White

So, green it is?
posted by nthdegx at 2:48 PM on June 8, 2005

The Ground is Green. Remember the saying. White is normally a grounded conductor (neutral), but I don't recall any useful pneumonics for it.
posted by Civil_Disobedient at 3:18 PM on June 8, 2005

Multimeter is easiest and the long term cost is the lowest, but in the short term:
buy a light bulb, a battery clip, a socket, and alligator clips.
Put the bulb in the socket. Connect a clip from one side of the socket to one wire from the battery holder with a clip. Connect one end of a clip that I will name "phil" to the other side of the socket. Connect one end of another clip that I will name "janet" to the other wire on the battery clip.
Touch phil and janet, make sure the bulb lights.
Look at the circuit board for the mouse and find the biggest patch of solder on the board. Clip phil to a pin that goes through that patch of solder. Touch janet to colored wire until the bulb lights.
posted by plinth at 6:51 PM on June 8, 2005

Yes, ground (very often) = green. You should be all right.
posted by jenovus at 7:01 PM on June 8, 2005

I wouldn't trust a color code on anything as cheap as a DB9 cable[1] if there is any possibility at all that a component at either end could be damaged. You can buy a continuity tester for a couple bucks.

[1] For example OEM USB cables have gone way down in the last couple of months. I've got one on my desk here with the USB symbol on both sides and one with it on the wrong side.
posted by Mitheral at 11:34 AM on June 9, 2005

Via a process of trial and error, it turned out to be the orange.
posted by nthdegx at 3:42 PM on June 9, 2005