EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: electronics-whiz on February 21, 2015, 08:19:58 pm
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I pulled a touch pad from a junk laptop a while back. I saved it with thought of adding some cable and using it as a mouse.
This is the info on the pad itself: JCI-s1S H, Logitech touchpad. A sticker on it says 904251-0000
There are a few SMD passive parts, and an IC. The IC says this on it: Zilog (C) 97 logitech, 331060-0050, 9750, 45
(Commas separate numbers either on different line, or greatly separated.)
It has an 8 pin Ribbon wire lead on the touchpad. It appears pins 7,8 are not used as just go to traces with nothing attached.
Looking at the trace size by the ribbon connector it seems pins 1, 6 are power and pins 2-5 are some form of data because they connect direct to the IC on the touchpad.
I can't find info for connection on the pad or the IC. Most things say the pad is PS/2 which makes since for the (C)97 on the pad. PS/2 only uses 4 pins though. 2 power, 2 data. I have 4 pins going into the IC. I don't have any click buttons for this so possible they were on the motherboard and sent back using 2 of the traces.
I don't have a scope or anything to analyze the data, also not sure what the power polarity is on those 2 pins.
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The pad I recovered from a dead Compaq laptop some time ago used USB for the connection, although the pinout was NOT standard USB. Your only hint is that sometimes the ground connection has wider traces, after that it's pure guesswork.
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A quick Googling around shows this:
http://pinoutsguide.com/Inputs/alps_touchpad_pinout.shtml (http://pinoutsguide.com/Inputs/alps_touchpad_pinout.shtml)
One of the first documents here is a maintenance manual for a laptop that uses this model of touchpad:
http://www.datasheetarchive.com/904251-datasheet.html (http://www.datasheetarchive.com/904251-datasheet.html)
It confirms that the buttons are to be grounded to activate, and a Synaptics document here (http://www.synaptics.com/sites/default/files/ACF126.pdf) also shows their touchpads used the same pinout.
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I used the pinouts guide link. It looks like I may be dealing with the bottom table with the 8 pins. Seems is setup like I thought and buttons sit on another PCB and link back up to the chip.
I'll give it a try sometime. I may have to get hands on a PS/2 cable. I had one once, but think I used it for wire in a project.