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Thread: Synaptics Touchpad TM41PUK324

  1. #1
    Newbie boridragon02's Avatar
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    Question Synaptics Touchpad TM41PUK324

    Hey everyone, I'm trying to convert a Synaptics Touchpad,Model # TM41PUK324, I recently took out of a Compaq Armada E500 to a ps/2 connection, but I'm not quite sure what the pinouts are. I looked at the synaptics touchpad interface document, but my model isn't mentioned there, and it doesn't have flat ribbon cable, it uses a 4 pin connection cable that goes straight from the touchpad's board to the motherboard. Would those be the 4 pins I could use for the ps/2 connection?

    The 4 Pins are:
    1. Black
    2. Brown
    3. Red
    4. Orangish Yellow

    Synaptics Interfacing Guide & Other Docs:
    http://www.synaptics.com/support/dev_support.cfm

  2. #2
    Maximum Bitrate mushin's Avatar
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    Most likely yes. Check out one of the couple existing threads that detail how you might go about identifying those pins if you cannot find the pinout.

  3. #3
    Newbie boridragon02's Avatar
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    ok i chopped a ps2 cable off of an old compaq mouse i had lying around and it also had 4 pins, 3 of the colors matched up and the 4th didn't. The orangish-yellow, black, and red colored wires were in both the mouse and touchpad connection, so i tried just connecting these to see if they matched up, and then tried just connection the 4th set of wires (brown wire from touchpad to yellow wire in ps/2 cord) The result?? Once i plugged in the ps/2 cable into my laptop, the touchpad got VERY HOT after just a few seconds, and I had to unplug it before it started 2 burn me and put it down to let it cool. Now, obviously that didn't work, but any clue what I might be able to do? I can't find the pinout for my specific model, and special instructions u can offer?

  4. #4
    Maximum Bitrate mushin's Avatar
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    I want to be helpful but it's hard when you apparently ignore my advice. Did you even try searching the forum? About 10 posts down (at the moment) is this thread which covers what there is to cover.

    Good luck.

  5. #5
    Newbie boridragon02's Avatar
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    Mushin, sorry, i didn't mean to make u feel as though ur advice was ignored. I did my searching of this forum on this topic and that thread was one of the first I found. However, the specific advice it offers doesn't match my model and its 4 pin connection type, and its general advice hasn't helped me to identify the pinouts yet.

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    curious you got any luck with that touchpad yet? I have the exact same model as well. I hope you did not blew up something on it from what you mention getting real hot.

    Only thing im definite by looking at the pcb is the ground lol, red here looks ambiguous to the +5 v, judging by the other pin layouts provided in thier websites. But anxious as I am I did a test and error try with Black - ground, Brown - Data, Red - +5v, Orange - Clock. However nothing responded, as i havent installed the driver as well but I dont think i need it. Hmm I will try installing it later however. Tell me if you got it working.

    Pin 1 (black) - ground
    Pin 2 (Brown)
    Pin 3 (Red)
    Pin 4 (Orange)

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    I too am trying to get one of these figured out, I've just spent the last few hours very carefully looking at the PCB and the 48 pin T1004 ASIC. I can conclude the following:

    pins 1-5 on the ASIC appear to go nowhere
    pins 6 and 7 are the Left and Right button inputs
    pins 8 and 9 appear to go nowhere
    pins 10 and 11 go to pin 3 and 2 (red and brown) on the electrical interface
    pin 12 appears to go nowhere
    pin 22 goes to pin 1 (black) on the electrical interface

    27 of the 48 pins are dedicated to X and Y

    The other pins go off onto other (mostly unused) circuitry, either with resistors and capacitors terminating one another, ultimately ending up either back at the ASIC, at ground or at what appears to be an unused interface labelled Y1

    Now, back in terms of the electrical interface, pin 4 (orange) appears to go nowhere.

    So we have a 4 pin cable for a 4 pin interface (PS/2) and only 3 of the pins appear to be in use. So from this I currently have two theories:

    1. That the Orange cable is for a circuit that is useful to PS/2 but not to the touchpad. Considering that the 4 PS/2 circuits are +5V, DATA, CLK and GND, I'm going to go ahead and say that if this is the case, it is CLK that isn't required by the touchpad. I assume that if this were the case, the T1004 would be running at a standard clockrate or sync'ing up in some other way, such as via DATA.

    Therefore, if this is the case, it's likely that red and black are +5V and GND respectively, leaving brown as DATA.

    The more likely theory at the moment however is this:
    2. Looking at the PCB, it's apparent that this is an overglorified capacitor... that's what touchpads are - capacitive, which is why yours got really hot when it was miswired - it was storing charge like a small battery.

    The PCB is primarily a big GND, and uses current passing tape to electrically ground to the chassis of the E500, which goes all the way around to where the ports are, including the PS/2 port. The important thing to note is that this potentially gives us our fourth electrical circuit!

    So in this theory, red is +5V, brown and black are DATA and CLK (I'm undecided on the order) and anywhere on the PCB's plentiful ground rail is GND. Either way, this reduces the number of possible combinations on the cable.

    Seeing as Synaptics seem to have plenty of useful documentation for interfacing to their equipment, I've tried to get in touch with them to see if they can shed some light on this, but there's been no response yet.

    I'm also trying to get another dead E500 so that I can really rip one of these apart - I need to shave the touchpad layer off the other side of the PCB to check out the circuitry on that side to get a more complete understanding, but as it is, I'm not willing to do that to my one and only device.

    Hope this helps someone. If someone is willing to guinea pig one of their touchpads to test the above two theories, please do so and let me know how you get on.

    Standard disclaimers apply - if the touchpad explodes, taking off your arm and killing your pets, I take no responsibility

    Keyword for Google crawlers - Compaq SPS 135227-001

  8. #8
    Maximum Bitrate mushin's Avatar
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    I think you can throw theory 1 out. The PS/2 protocol requires both data and clk to work. Theory 2, while possible, is rather suspect too... I'd be very surprised if the GND on the PS/2 plug wasn't directly connected to GND on the pad. Are you absolutely certain orange goes nowhere? Because the obvious guess would be red = 5V, black = GND, orange/brown = clk/data.

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    I've taken a good long look at it. The pin is soldered to the PCB, but there's no traces going to it at all. If it's connected anywhere, it's on the other side of the PCB, hence why I want to get another one to sacrifice in the name of knowledge.

    The other thing I could do is dig up a dead E500 mobo at work and do some pin tracing on that side, but as it stands I'm sure that GND is going via a common E500 GND Rail

  10. #10
    Maximum Bitrate mushin's Avatar
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    Have you tried checking continuity between that pin and ASIC pins?

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