T400 Keyboard: Trackpoint Pinout


24 Mar 2014, 21:58


I'd like to add a Trackpoint to a keyboard project of mine. One I could easily salvage comes from a T400 internal keyboard, P/No: 42T3109. I believe it's a PS2 controller on the chip (PTPM754DR, same chip as on other Trackpoint controllers used for keyboard hacks in this forum),. What puzzles me are the 8 lines instead of 10 I see on other trackpoints.

Does someone recognize this controller and point me to the correct Pinout for the flex wire solder points?

Attached are some pictures of the PCB.
E5248912.JPG (190.26 KiB) Viewed 5696 times
E5248911.JPG (206.69 KiB) Viewed 5696 times

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12 Feb 2016, 23:53

sorry for necroposting on this one but I just scavenged some seconds ago the very same trackpoint to re-purpose it in my DIY keyboard I'm building right now... and I also was kind of "surprised" by the 8 pins instead of 10...

did you maybe solve and get to the correct pin-out in the end? :)



14 Feb 2016, 12:03

Sorry, I haven't investigated this further.

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15 Feb 2016, 23:51

to me, starting to count the pins from 1-8 from the bottom of your 1st picture, it seems that pin 5 could be VCC and pin 7 GND (I still have doubt it could be the inverse so still not trying it out at the moment..) because I see those two are the biggest traces and the 5 in particular goes first into a resistor and then to some other quite large areas (especially on the surroundings of the holes), so might indeed be.. even if also GND is usually covering large areas on pcbs to reduce interferences... I'm trying still to locate the ASIC (BU6341FV or BU6382EFV) I have.. in yours it seems to be another one tough (PTPM754DR).. if I'll not succeed I'd need to harvest another one and it will be even more timeconsuming.. or not? :)

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18 Feb 2016, 12:15

I was able to reverse a bit also another one.. : post287301.html#p287301

Did you also perform readings on a scope for this one so far?

Do you maybe also still have the orange flat connector that was connected to it? If you look at it gnd vcc and the mouse buttons should be easy to find out..

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18 Feb 2016, 23:54

I was finally successful in reversing this trackpoint pinout as well (starting from the pin that is highest up in your picture being the 1st pin):
1- reset (0V reading)
2- 5V
3- Clock (freq reading)
4- Ground
5- Mousebutton0
6- Mousebutton1
7- Data (5v reading)
8- Mousebutton2
Confirmed with tmk.

Last edited by tentator on 24 Feb 2016, 00:41, edited 1 time in total.

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19 Feb 2016, 00:04

here a picture of the permutation test :)

the trick is:
a) make sure you have a correctly running tmk SW that supports PS2 mouse (the best is a .HEX that somebody else confirmed to be working)
b) ground and vcc are recognizable usually because they have big traces, gnd being also easy to find out with a tester then
c) mouse buttons should also be easy to trace back by following the tracks to the buttons
d) the reset when powered on is the only remaining pin that reads 0V
e) the clock and data will show 5v an easy trial or scaning for frequencies on the pins with a scope or so does the final rule-out
photo109275380194585616.jpg (114.69 KiB) Viewed 5191 times

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24 Feb 2016, 00:55

For other fellas with similar needs, I post here some pictures of the currently reversed trackpoint modules as well:
LVMV (MB0 = Left; MB1 = Right; MB2 = Middle Click)
LVMV (MB0 = Left; MB1 = Right; MB2 = Middle Click)
pinout-trackpoint-LVMV.JPG (263.28 KiB) Viewed 5143 times
pinout-trackpoint-LVC9.jpg (726.5 KiB) Viewed 5143 times
kn39EHa.png (980.54 KiB) Viewed 5143 times
R61 back.JPG (90.07 KiB) Viewed 5143 times
tpkb_07.jpg (28.27 KiB) Viewed 5143 times
If you happen to find others feel free to post them here.. :)

Last edited by tentator on 01 Mar 2016, 22:53, edited 1 time in total.

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24 Feb 2016, 01:24

Ooh, I will definitely be in touch for more details, tent. I need more trackpoint in my life!


24 Feb 2016, 02:25

tentator wrote: For other fellas with similar needs, I post here some pictures of the currently reversed trackpoint modules as well:
Wow.. Great work! It would be worthwhile to cross-post it here to have more info in one place. In fact, it probably makes sense to start a wiki page. Do you have any objection to your images on the DT wiki? I'd be willing to add it if you like.

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24 Feb 2016, 07:52

Yes of course would make sense!
But most of the pictures are not mine just from other posts or from around and I added some legends on them :)
Otherwise I really wonder why there hasn't been more trackpoint so far on regular keyboards.. or at least something similar.. ;)

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28 Feb 2016, 02:31

I drew the T40 schematic, feel free to post it anywhere you want - however, I shamelessly ripped the photo of the board on it from some other TrackPoint thread, either here on Deskthority or on geekhack. I don't remember which and can't speak for the photo author.

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09 Mar 2016, 22:19

Good work, there appear to be more types of trackpoint still.

For admins: wouldn't it make sense to somehow merge this with the thread I started a while ago? Here it is:

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09 Mar 2016, 23:42

one of your two trackpoints seem the same found here the other most probably you have to reverse it but should be easy.. do you have a picture of the back of the trackpoint and maybe also have still that orange flat that was connecting it to the laptop? that one makes it even more easy to reverse the pinout: the 3 mouse buttons are easily spotted because go to the keyboard and the two thicker signals for GND and VCC are easy to see too, the ground in particular, so you will only need to make a couple of guesses for rst, data and clock or use a meter to see what you read on them when first powering it up..



01 Apr 2016, 17:38

I found two trackpoints. I did some measurments to find the pinout. Please could some review if the following pinouts (of the ICs) are correct?

1st: IC = PTPM54DR
28 Clock
31 Button input 1
30 Button input 2
29 Button input 3

2nd: IC = PTPM54A DR
27 Clock
28 Button input 1
29 Button input 2
30 Button input 3

Correct? I think something is wrong because of the difference.

Were do I found code/ a library for AVR microcontrollers (atmega...)

Thank you for your help.

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01 Apr 2016, 17:59

are you interested in the chip pins or in the pinout of the whole trackpoint?
if you can make a couple of pictures of the IC/PCB it would help as well..



03 Apr 2016, 18:40

I would be interested in the pinout of the IC. With it I can measure the connections to the connector or testpoints.

I did measurements on the 2 Trackpoint boards. Now I am shure that the both ICs don't have the same pinout. But they have both 32 pins and the labeling is almost the same:

IC 1:
PTPM754DR Pinout like in the datasheet of the old IC TPM754, you have to omit the pins 15, 16, 17 and 18 of the PTPM754DR (they are connected to GND), the other pins are the same as on boh IC versions
(https://www.mikrocontroller.net/attachm ... tpm754.pdf)

IC 2: PTPM754A_DR, not the same pinout as IC 1, Data is on the same pin, Clock not

Pinout details:

IC 1:
Trackpoint Lenovo ... :
Connector PTPM54DR-Pin Function
1 2 Data
2 5 Reset
3 31 Button
4 30 Button
5 29 Button
6 28 Clock
9 nc (not connected)
10 nc (not connected)
11 nc (not connected)
12 nc (not connected)

PTPM54DR Pinout:
GND: 8, 13, 15, 16, 17, 18, 32
VCC: 26

IC 2:
Trackpoint HP Compaq TC1100
Connector PTPM54A_DR-Pin Function
4 2 Data
5 27 Clock
6 28 Button
7 29 Button
8 30 Button

PTPM54A_DR Pinout
GND: 3, 9, 15
VCC: 16, 25
IC_1_PTPM754DR_.jpg (861 KiB) Viewed 4799 times
IC_2_PTPM754A_DR_.jpg (940.17 KiB) Viewed 4799 times
For IC 1 I wired the connections corresponding the schematic in this thread (4.7K pullups on Clock and Data, 2.2u and 100k on Reset).
Then I connected the circuit to an arduino uno (atmega328) with the PS/2 test sketch. But it didn't worked (the sketch should print out the mouse-data on UART/RS232)
The sketch works for an ps/2 mouse but not for this trackpoint.

Does anyone know working ps/2 mouse firmware for atmega328 or atmega2560? (or do I need a teensy?)
Does the tmk_keyboard firmware work for such a trackpoint/ ps2/mouse? (https://github.com/tmk/tmk_keyboard)
If yes, which part of this repository should I build and flash?
I think the ps/2_usb converter of the tmk_keyboard repo works only for keyboards. Am I right? (https://github.com/tmk/tmk_keyboard/tre ... er/ps2_usb)

At the moment I don't really need a firmware which works as USB-HID, I would be happy if I see some debug-info over UART/RS232.

Thanks for your help.

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04 Apr 2016, 00:06

uhm, looks good and should work.
Try to use my fork and see: https://github.com/tentator/tmk_keyboar ... /tentboard
in practice Makefile and config.h have the interesting parts at the end included to activate trackpoint via ps2 on the tmk firmware, but of course you have to doublecheck which pin corresponds to what on the arduino.. if you use PS2 INT it should be easy to see in the arduino which are the two pins you should use as data and clock.. in usart mode they should be PIN7 and PIN23 on arduino side.. maybe better you doublecheck here the mapping between arduino and teensy: https://www.pjrc.com/teensy/card2b.pdf :)
And let me know,

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