DYI USB Touchpad Synaptics TM2334 - Page 1
Forum section: electronics / projects

author: Sway07
author_rank: Contributor
timestamp: September 09, 2021, 04:00:35 pm
content: Hello,I want to make a laptop powered by RPI 400 and I thought I will try to repurpose old touchpad I have laying around. I'm going to list things I think are correct based on looking around/ probing.This is a ps/2 touchpadT22 - VCC - pin 4 on female ps/2T23 and the huge pad on the right - GND pin 3 on female ps/2T13 - Data - pin 1 on female ps/2T12 - CLK - pin 5 on female ps/2In windows it doesn't want to work for some reason, even tho it shows up as a "HID - compliant mouse" in device manager. What I tried was removing the device in windows and trying to change T12 and T13 (Was that a stupid thing that could've destroyed it?).PS Yes, I managed to rip one of the pads. That is also the reason why two of the wires are blue. I don't have any thin red wire on hand and when I used the one I have I ripped the padThank you in advance for any insight/tips/knowledge.

author: dferyance
author_rank: Regular Contributor
timestamp: September 09, 2021, 05:28:08 pm
content: You need a way to check the signals. If you have a scope or logic analyzer use that. If not, do you have an arduino or some other 5v MCU you can use? If you have an arduino you could also probably find a sketch that sends ps/2 data that you could use to verify the port and your assumptions are correct.

author: magic
author_rank: Super Contributor
timestamp: September 09, 2021, 06:27:04 pm
content: Swapping clock and data is unlikely to cause damage, they are electrically identical signals (and quite safe - open collector), only their meaning is different.What can cause permanent damage in some PS/2 hosts and/or devices is loss of ground connection, and that's a situation which may temporarily occur if you hotplug PS/2. Many devices are OK, but technically you are not supposed to do that.Are you sure that thing doesn't require some drivers in Windows?

author: Sway07
author_rank: Contributor
timestamp: September 09, 2021, 09:47:21 pm
content: Quote from: dferyance on September 09, 2021, 05:28:08 pmI don't have a scope but I do have an arduino laying around. So I'll have look at that

author: Sway07
author_rank: Contributor
timestamp: September 09, 2021, 09:53:16 pm
content: Quote from: magic on September 09, 2021, 06:27:04 pmGround should be the only pin that I unintentionally made sure it doesn't fall out. Because I used a male header pin soldered to a wire and that fits in the ps2 plug really tightlyI think it should be work as it is. Because I'm trying it on a laptop that already has a touchpad that I think should be from synaptics (I haven't seen a lenovo laptop without synaptics touchpad). But I'll also give it a shot.Thanks for the tips I'll post an update tomorrow

author: gabiz_ro
author_rank: Regular Contributor
timestamp: September 10, 2021, 06:55:46 am
content: Ideapad Z510 touchpad looks simillar to this,maybe the same.On schematics pinouts are1 +3VS2 TP_CLK (touchpad clock)3 TP_DATA (touchpad data)4 GND5 SMB_CLK (smbus clock)6 SMB_DATA (smbus data)As resultT22 VccT? TP_CLK (could be T6 but not sure,check if T6 is on pin 2 of connector)T8 TP_DATAT23 GND

author: Sway07
author_rank: Contributor
timestamp: September 10, 2021, 07:18:46 am
content: Quote from: gabiz_ro on September 10, 2021, 06:55:46 amYes, it's a touchpad from lenovo z510. If I go from left to right the pins connected to the test pads are: T13; T12; T17 and T23; T8; T6; T20 and T22. So T6 can be pin 2 if you count from the right .

author: gabiz_ro
author_rank: Regular Contributor
timestamp: September 10, 2021, 07:26:05 am
content: J1 have marked pins 1 - 6Try pinout I said early.Also you may try to add 2 or 3 diodes series from Vcc 5V to T22 maybe chip doesn't like 5V

author: Sway07
author_rank: Contributor
timestamp: September 10, 2021, 08:28:02 am
content: Quote from: gabiz_ro on September 10, 2021, 07:26:05 amAlright I tried it, and still it doesn't work. I also tried getting a driver. That didn't help either.

author: gabiz_ro
author_rank: Regular Contributor
timestamp: September 10, 2021, 08:45:29 am
content: In both cases show as "HID - compliant mouse" in device manager?What HWID ?Some notebooks have on-off for touchpad, (don't remember if in off state still visible in device manager) maybe there is need some command via smbus to enable ?

author: Sway07
author_rank: Contributor
timestamp: September 10, 2021, 09:32:20 am
content: Quote from: gabiz_ro on September 10, 2021, 08:45:29 amAlright, so I did couple of things. I looked up, how tutorials. All of them show the touchpad working right after connecting them to the ps/2 to usb converter. So I thought I would try connecting it straight into an old PC I have laying around. And because I don't double check stuff I was connecting the wires while the pc was plugged in and there was a pretty noticeable spark on the VCC pin (PC still turns on and works, no pc was harmed). I'm not really sure if this it's worth it to continue trying to troubleshoot something that most likely doesn't have the magic smoke. Another project fixed until it's broken.HID compliant mouse is just a fallback option in windows when it doesn't have a better name. It stands for "Human input device" and compliant should mean, that it works with USB.Thank you to everyone that responded