Author Topic: Lenovo T420 - disabling touchpad  (Read 2586 times)

Andi B.

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Lenovo T420 - disabling touchpad
« on: April 24, 2018, 02:37:07 pm »
As I like trackpoints and dislike touchpads I usually disable touchpads in BIOS to get ride of this annoying peace of hardware. IIRC with my previous Thinkpads (T41/42p/43/60/R50...) only the touchpad is disabled but not the keys on top of the touchpad. The T420 behaves different. Not only the touchpad but also the surrounding keys do not work anymore. But I need these keys to emulate the mouse buttons.

How can I disable the touchpad but not the keys?

Doug Bissett

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Re: Lenovo T420 - disabling touchpad
« Reply #1 on: April 24, 2018, 05:47:05 pm »
Quote
How can I disable the touchpad but not the keys?

In my T510, there is a BIOS option to enable/disable the touchpad and/or the stickmouse. That works as you would expect. Disabling the touchpad disables the touchpad and the associated buttons. It leaves the stickmouse, and the associated buttons working. On my L530, there is no setting for that stuff. The windows driver has settings, that work as expected, but that does me no good in OS/2. My solution is to tape a heavy piece of cardboard (not corrugated) over the touchpad, leaving the mouse "buttons" exposed. That works pretty well, especially when I also use a wireless mouse.

Martin Iturbide

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Re: Lenovo T420 - disabling touchpad
« Reply #2 on: April 25, 2018, 03:06:14 am »
Hi

As far as I know there is no utility/driver that can help with that on OS/2 / ArcaOS. On Windows there is the utility on "Control Panel - Mouse" to enable/disable the Touchpad with its buttons (bottom) and to enable/disable the Trackpoint with its two buttons.  (Attached Picture)

Something that may complicate things for us is that I had noticed that Trackpoints/Touchpads in Thinkpads now came in three brands, Synapsis Synaptics, ELAN and Alps. So I'm not sure if we can get a solution that can fit it all. The T420 seems to come with the Synaptics one according the support site.

Regards

Update: Just to correct I misspelled Synaptics.
« Last Edit: April 27, 2018, 03:05:49 pm by Martin Iturbide »
Martin Iturbide
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nyao

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Re: Lenovo T420 - disabling touchpad
« Reply #3 on: April 27, 2018, 02:14:13 am »
Hi,I am using ThinkPad E440.
This is also a model that can not set the touch pad from the BIOS.
Because there are too many malfunctions, we have pasted aluminum tape.
To be honest, I have not worth using ArcaOS on my laptop :'(

Andi B.

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Re: Lenovo T420 - disabling touchpad
« Reply #4 on: April 27, 2018, 08:17:36 am »
Thanks for the inputs. When time permits I'll take another look into the BIOS. Maybe I disassemble that toy (I can't take this for serious work cause the low display resolution) and cut some wires to see if I can get it to work the way I like. As a last resort I'll try the 'shielding plate' solution.

Martin Iturbide

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Re: Lenovo T420 - disabling touchpad
« Reply #5 on: April 27, 2018, 03:04:23 pm »
Hi

Maybe an interesting start point to try to solve this issue on OS/2 can be to look around on the Linux community for any driver and source code that they may have for this three brands (Synaptics, ELAN and Alps). After that the real  effort will be to understand that source code and see how it can be recreated from our community.

The issue is that I don't understand anything about drivers source code :)
https://github.com/torvalds/linux/tree/master/drivers/input/mouse

Regards
« Last Edit: April 27, 2018, 03:13:17 pm by Martin Iturbide »
Martin Iturbide
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Andi B.

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Re: Lenovo T420 - disabling touchpad
« Reply #6 on: April 27, 2018, 03:41:27 pm »
@Martin - I estimate disassembling and cutting the right wire would not take more than 15 minutes.If the keys are not tightly integrated into the touchpad. Have to look at it when at home.

Although understanding a bit programming I would estimate to write, debug, making a GUI for configuration and an installer for such thing would take a few months. Simple math says it would need way more than thousand notebooks with crippled BIOS (touch not to disable separately from the keys) so it would be worth the effort ;)

ivan

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Re: Lenovo T420 - disabling touchpad
« Reply #7 on: April 28, 2018, 12:33:42 am »
Hi Andi,

After many years of delving into the guts of computers and laptops/notebooks your idea of cutting wires to touchpads is a no go.  Most of the touchpads are an integrated sub unit that usually presents a usb interface to the hardware.  To isolate/separate various functions would require major work in the touchpad circuit board and cutting the wrong track could well stop everything there working.

The two scans show a typical touchpad layout.

Andy Willis

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Re: Lenovo T420 - disabling touchpad
« Reply #8 on: April 28, 2018, 04:35:02 am »
My T420 BIOS:
Config - Keyboard/Mouse - Touch Pad [Disabled]

Right above Touch Pad - TrackPoint [Enabled]

Ian Manners

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Re: Lenovo T420 - disabling touchpad
« Reply #9 on: April 28, 2018, 08:23:51 am »
Hi Ivan,

In 0-0-touchpad-1.jpg, what happens if you flip the cable grip up and remove the Mylar flat cable?
Hard to tell with the picture but do the button's control go back out to the MB or do they go to the touch PCB?
Flip the grip up and remove the flat cable and try it. Be gentle with the grip socket though, as they can sometimes break easily.

If the button activation is part of the touch controller board then what I would normally do, would not work either, that is to remove the fuse near the plug on the touchpad PCB (normally a black 0 resistor).
Cheers
Ian B Manners

ivan

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Re: Lenovo T420 - disabling touchpad
« Reply #10 on: April 28, 2018, 02:42:28 pm »
Hi Ian,

The Mylar cable between the circuit board and the switch board is double sided - one side connects the switches to the board and the other side takes the output from the board across to the output Mylar cable.  I assume this layout is to allow for different switch plate layouts while using the standard touchplate circuit board.

As far as I know the the touchpad controller also integrates the switch pulses because of the tapping function and multi swipe - if everything didn't go through the controller you would end up with very interesting things trying to happen.

The unit in the pictures is about 5 years old, pulled from an Acer laptop that got rather damp in a fire.  Much newer ones appear to follow the same configuration as an all or nothing setup.
 

Doug Bissett

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Re: Lenovo T420 - disabling touchpad
« Reply #11 on: April 28, 2018, 07:00:18 pm »
Quote
I estimate disassembling and cutting the right wire would not take more than 15 minutes

When I got my L530, I looked at what needed to happen to disable the touchpad. There is a ribbon cable, that appears to be unique to the touchpad. I unplugged it, and tried the machine. I don't remember if it was BIOS, or windows 7, that had a complete breakdown over the missing part (no, it is NOT USB). I just put it back together, and went for the cardboard taped over the touchpad. The L530 was new, at the time, so I wasn't about to do more than disconnect a cable that could be plugged in again. I certainly would not be cutting anything that cannot be easily connected again. You could end up with a machine that won't work, at all, and no way to fix it, without spending more than you might like.

Ian Manners

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Re: Lenovo T420 - disabling touchpad
« Reply #12 on: April 28, 2018, 07:22:19 pm »
I don't have any triple digit models, happy with what I have, they all still work :) but went and disassembled a few thinkpads to refresh my memory, all the ones here, the buttons below the touchpad are controlled by the chip on the PCB under the touchpad. The buttons (2 or 3 depending on model) above the touch pad are part of the keyboard which would be logical, keep them as part of the stick so use a different controller though really, everything is programmable.

However..
The two buttons below the touchpad on my TP R61 are not integrated, they have separate lines via a lead to the touchpad controller which are simply directed to the plug that goes to the MB.
The two buttons below the touchpad on my TP R61i (model without fingerprint thingy) go through the touchpad controller, they do not have separate lines so it seems to be very much a try it and see thing even depending on similar models. Not that this helps Andi but it does answer a sidetracked curiosity.

Maybe Andy's pointing to his setup will help Andi, if not looks likes it's time for some foil. I would not cut any Mylar cables unless you have spares!
Cheers
Ian B Manners

Andi B.

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Re: Lenovo T420 - disabling touchpad
« Reply #13 on: April 29, 2018, 07:06:53 pm »
Another annoying problem with the T420 is even with enabled touchpad the keys at the bottom are used as mouse buttons. On older models (T60, T42p...) both the top keys near the space button and the bottom keys can be used. Another show stopper for using this notebook with OS/2 :( Though given the low resolution (1366x768) I never considered the T420 using for real work. Only for testing some stuff.

Andi B.

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Re: Lenovo T420 - disabling touchpad
« Reply #14 on: May 09, 2018, 11:08:26 pm »
Now I had a look at the keys and touchpad. As usual with Thinkpads disassemble is quite easy. Two screws and the well know Thinkpad keyboard design can be lifted up. Attached some pictures. As we see the keys I want to use (that one near the space bar) are not part of the touchpad but of keyboard electronics. So I though maybe I can read out these keys the same as the other keys/mouse messages. But I did not find any utility which reacts on these keys. AFAIK the keyboard/trackpoint is attached to the system via PS/2. So the trackpoint and the 3 keys emulates a PS/2 mouse. Seems this is all old well known legacy stuff.

After that I discovered that these keys do not even work with Windoze10. Tried the W10 drivers I found at Lenovo but can not make these mouse keys work. Regardless which settings I tried. Though I'm no Win expert and don't want spend much time with this rubbish peace of shitty malware. Anyway if it does not even work with Win I started to believe these keys are broken.

I remember there were ISO images with DOS tools for older Thinkpads to test various hardware components. I think to remember there was a keyboard test too. Anyone knows such basic hardware test tool for the T420?

Do these keys (below space bar) work for others with the T420? With OS/2 or Win?
« Last Edit: May 09, 2018, 11:12:09 pm by Andi B. »