IBM Model F BigFoot... 8521

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Jaki1122

18 Mar 2020, 03:17

Hello everyone, hope you are doing well.
So, I got a Model F 8521, a model that certainly is not that popular as I thought it would be. Well its just a normal BigFoot, but with Spanish layout and legends. I'm currently in the process of building a controller (not adaptor, as this model doesn't have any CPU!) so it can be used with a modern USB connector. I was following this thread https://geekhack.org/index.php?topic=48950.0 when I ran into a little problem. The connector that used to go to the terminal has the missing pin in another place, and VCC is also misplaced, and for the keyboard itself, I have jumpers on positions 1,2, 4 whereas all the rest seems to have the jumpers shorted only at position 0.
My guess is that this keyboard is exactly like the others, and that I only need tho change the jumpers and wire it directly from the board to a Pro Micro, like everyone does, however, I would like to be sure that there is no further difference, so that's my question: is it any different from the other Big Foot out there?
As always, thanks a lot for your help!

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Jaki1122

18 Mar 2020, 03:22

Some attached pictures!
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orihalcon

18 Mar 2020, 04:28

If you have access to a regular XT capsense PCB, since the layout is the same, you can just change capsense PCBs (which has the controller on it) that and you'll have an easy to convert XT signal and you could even use the XT's original cable if you so choose. I've made this suggestion a few different times on different threads and I can't say I've seen anyone actually do it, but I see no reason why it shouldn't work given that the layout is the same and I'd have to assume that the retaining clips that hold the capsense PCB down to the backplate are also in the same places.

I don't have a bigfoot to try it with myself, but if I did, I'd probably go the Model F XT PCB route if you can get one without having to pay international shipping rates. Alternately, you might just totally swap XT guts into your case if the backplate uses the same mounting as the XT.

Other thing you could do is chop off the original controller and handwire to commonsense or Xwhatsit, like I have done here: viewtopic.php?t=19522

User avatar
Redmaus
Gotta start somewhere

18 Mar 2020, 06:08

I agree with Orihalcon, I tried to convert my bigfoot with soarers awhile ago and couldn't ever get it to work. I'd recommend commonsense, since you can buy a Cypress controller for $10. Although it is a fair bit of work, both soldering and firmware.

Whatever route you do down, good luck!

John Doe

18 Mar 2020, 06:15

Redmaus wrote:
18 Mar 2020, 06:08
I agree with Orihalcon, I tried to convert my bigfoot with soarers awhile ago and couldn't ever get it to work. I'd recommend commonsense, since you can buy a Cypress controller for $10. Although it is a fair bit of work, both soldering and firmware.

Whatever route you do down, good luck!
Where is the link for the Cypress board with that price? I want to give a try for some boards now. :D :D

User avatar
Darkshado

18 Mar 2020, 06:43

orihalcon wrote:
18 Mar 2020, 04:28
Alternately, you might just totally swap XT guts into your case if the backplate uses the same mounting as the XT.
It does! Source: I have a "Bigfoot" case with an XT assembly installed.

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karlmartin95

18 Mar 2020, 23:55

I have the same bigfoot and I did the conversion without a problem using an arduino pro micro and soarer software. Be aware, if using pro micro you have to desolder the TX or RX resistor (i don't remember exactly which one was) in order to have access to one pin of the pinout recommended.

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karlmartin95

18 Mar 2020, 23:57

KarlMartin#7820 is my account on Discord, add me and I'll guide you through the process in english or spanish, as you wish.

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Redmaus
Gotta start somewhere

19 Mar 2020, 00:02

John Doe wrote:
18 Mar 2020, 06:15
Where is the link for the Cypress board with that price? I want to give a try for some boards now. :D :D
Here is the link for the cypress: https://www.cypress.com/documentation/d ... rammer-and

Also Snacks made a great guide on using commonsense on model F's and beamsprings, his guide is here:
viewtopic.php?t=21899

User avatar
Jaki1122

20 Mar 2020, 05:45

Hey everyone, thanks for all the responses, and sorry for not coming here for a couple of days. Anyway, the Cypress board concept is quite interesting, obviously it can also be done with an Arduino that has HID compatiblity (ATMEGA32u4 for example) and enough pins, but of course, the Cypress is cheap and there is a very VERY simple guide to follow so... why work more? At the end, I'm nothing but a lazy boy :)
Considering we are all in cuarentine in our house, maybe, I'll put a single jumper on position 0 and try to make it run with a Pro Micro and a Soarer's controller, assuming the circuits are 100% identical to all other bigfoots, as it really seems to be the case. Worst case scenario, I burn the PCB, that will go off anyway as its replaced with a Cypress board or similar, so nothing to lose. I'll keep you posted. Thanks everyone!

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