IBM 5251 Beamspring Xwhatsit converter problem.

[Fkazim]

Hello everyone I had finally finnished restoring my IBM 5251 Beamspring keyboard. I actually made a thread about the full restoration process here: viewtopic.php?f=7&t=22586. I seem to be having a problem where some keys are registering as the same keys. What I mean by that is that some keys output the same scan codes. Below is an image showing the specific keys that seem to be linked. If you guys could help me resolve this problem it would be much appreciated.

Thanks.

IBM 5251 linked keys.jpeg (103.39 KiB) Viewed 8849 times

[ZedTheMan]

Have you checked to see that the keys don't trigger each other's thresholds and that one doesn't override the other?

[Fkazim]

They do trigger eachother as they register as the same key. I just don't know why. I tried changing the thresholds but it's either I go low on the threshold and none of those keys I outlined register or I go higher on the threshold (141) and those keys In each square I outlined activate eachother. For now I have set left shift's pad to be ignored so my backslash works and I set the caps lock pad to also be ignored so that my tab key on top functions correctly.

Any help in fixing this problem would be much appreciated.

[Fkazim]

Any ideas to how to get the keys to activate independently?

Thanks.

[ZedTheMan]

I forget, can you set the threshold of independent keys in xwhatsit? If so, can you change the thresholds to be low for all but one specifically?

[AJM]

I would check, if the connector of the xwhatsit is lined up correctly with the pcb. The connector is wider than necessary. So it can be attached too far to the left or right. If this happens it can short two or more contacts, which might have such a strange effect.

[Fkazim]

Thanks for the advice will check that when I am back from my holiday.

Much appreciated.

[Fkazim]

Well I got back from holiday yesterday. I tried moving the Xwhatsit controller over on the edge connector to where it was all the way to the left side of the edge connector and it made my PC go absolutely insane with flickering black screening etc. So I don't think it is anything to do with the edge connector. any other ideas? I made sure the connector is definitely lined up correctly.

Thanks.

[Fkazim]

Any other ideas on this problem?

Please help.

[Fkazim]

Just Checked all the contacts on the edge connector and all seemed fine. Although I did still pull the capacitive pcb off of the backplate. I never realised how very thin the PCB is on the beamspring compared to the Model F's thick PCB. Anyway then I used some isopropyl alchohol and cleaned all the contacts but still no luck the problem stayed.

I really don't know where to go from here could it be the Xwhatsit that is causing the problem?

[listofoptions]

no its almost certainly the edge connector. ive restored a handful of 5251's its usually the only place they can stop working, even with corroded looking pcbs. get some 1k grit or higher sandpaper, and use some isopropanol to gently sand the connector. since you've got it apart already clean the pcb as a whole with a towel and either isopropanol or acetone. make sure there's ABSOLUTELY nothing on the flyplates, you might even have to clean them with a qtip and more iso.

[Fkazim]

OK will try that and let you know what happens I will probably report back this weekend really appreciate the input.

Thanks.

[listofoptions]

just make sure to be very careful in sanding that connector, you're only trying to break any oxide or light corrosion, if you see copper STOP!

[Fkazim]

OK will disassemble the keyboard again this weekend.

Thanks for the help.

[Fkazim]

I just finished sanding down the contacts on the edge connector. I can now see all the contacts are shiny but still have the same problem. Any ideas where to go from here?

Thanks.

[Fkazim]

So no other ideas?

[Fkazim]

OK so I have taken the keyboard completely apart again. I sanded the edge connector making sure that all the contacts are nice and shiny and not oxidised. Also I cleaned the capacitive pads on the PCB. I am pretty sure it is some sort of bug in the Xwhatsit firmware. As when checking all the traces on the PCB all looks to be good. Please let me know your opinions on if you think the PCB is at fault below I have posted a picture of the PCB.

Thanks.

IBM 5251 beamspring PCB.PNG (289.83 KiB) Viewed 7660 times

[Fkazim]

I still got the problem is it possible to custom set the capacitance in Capsense from e.g 150 to 150.4? As I thing I just am either way over and key are all actuating or I'm too low and not all keys respond.

Thanks.

[reavy]

I had this same problem trying to restore a 3178 and gave up. I even tried a different xwhatsit board thinking I may have damaged my first one somehow. I took the keyboard completely apart, cleaned everything, put it back together and still had the same symptoms.

One solvable thing that can cause problems is not carefully cleaning off flux residue from any soldering done. You can get away without cleaning flux residue in very simple DC circuits like LED lights, but for sensitive circuits like the capsense PCB, the conductivity of flux residue can be significant enough to cause problems.

[kmnov2017]

Port QMK onto Xwhatsit. Message user pandrei for help.

[reavy]

I've heard people mention QMK on xwhatsit, but it isn't clear to me what about QMK is better. Does QMK solve some capsense algorithmic problems that exist in xwhatsit's firmware?

[kmnov2017]

I've heard people mention QMK on xwhatsit, but it isn't clear to me what about QMK is better. Does QMK solve some capsense algorithmic problems that exist in xwhatsit's firmware?

With QMK ported onto the Xwhatsit controller, you wont be using the xwhatsit firmware anymore.

[reavy]

What I mean is, does QMK implement capacitive switch sensing in a way that is fundamentally better than the implementation in xwhatsit firmware?

[reavy]

As a follow-up, I've been working with pandrew to load the QMK firmware on one of my boards, and I confirmed with him that his QMK implementation does much more sophisticated capsense auto calibration than xwhatsit's original firmware. The board automatically calibrates on power-up (requires that no keys are being pressed while plugging in and/or powering on), and instead of a global threshold for the whole board, thresholds are binned so multiple thresholds can be used across different areas of the board as appropriate.

[keyboardist]

So, does it work now?