IBM Model F BigFoot... 8521

[Jaki1122]

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!

[Jaki1122]

Some attached pictures!

[orihalcon]

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

[Redmaus]

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]

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.

[Darkshado]

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.

[karlmartin95]

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.

[karlmartin95]

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

[Redmaus]

Where is the link for the Cypress board with that price? I want to give a try for some boards now.

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

[Jaki1122]

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!

[AngryCockroach]

Hi, did you make it run with the Arduino Pro Micro?
I have acquired three Bigfoots and would like to use the cheaper Pro Micros instead of the expensive Teensy or Micro (without Pro).

[sharktastica]

Hi, did you make it run with the Arduino Pro Micro?
I have acquired three Bigfoots and would like to use the cheaper Pro Micros instead of the expensive Teensy or Micro (without Pro).

If you're using Soarer's Controller firmware, it can work but with one modification. The firmware's (at least by default) use of pins was designed with Teensy 2.0 in mind, and one such pin it uses (PB0) is exposed on the Teensy 2.0 but is used internally for an LED (RXLED) on Pro Micros. You should be able to remove the LED's resistor and solder a wire onto its pads to recover the line. See my website for the full pinout you need to use for Soarer's Controller on Pro Micro.

[AngryCockroach]

Oh wow, thanks for the fast answer. You mean the black little one on the right?

Groß (IMG_3367).jpeg (239.23 KiB) Viewed 15081 times

That is very tiny... I soldered the legs on the micro several times for other Ms or Fs, but that tiny thing looks difficult....

[AngryCockroach]

I just saw teensy for under 10€ so I think I wait a little until they arrive before I destroy the pro micro…

Here are the bigfoots. I will paste pictures after the restorations.

IMG_3363_Original.jpeg (2.93 MiB) Viewed 15066 times

[AngryCockroach]

I now hooked up the teensy (with Soarer 1.2 beta) to two of the bigfoots but it does not work quit well:
Some key presses result in multiple character outputs and some keys do nothing at all. It is the same on both keyboards. So I assume it is no hardware error on the keyboards or the PCB.

I connected the teensy like shown in this thread: https://geekhack.org/index.php?topic=48950.0
I also tried switching out the grounding screw but same result.

Anyone knows more about the settings for the bigfoot in the Soarer Controller (debounce, ...) and what might help?

Edit:
I discovered something:
When I press M it outputs "nm". But when I hold the M key, it only outputs "m".
So the "n" comes in on the upstroke it seems. Same with other keys.

And I painted the last keyboard grey because the paint was damaged and I wanted the industrial look.

C2895F74-0AA5-4F83-87AE-40E8EC6B3A20.jpg (1.5 MiB) Viewed 10677 times

[AngryCockroach]

Do I have the 5291 or the 8521?

The product number suggests the 5291 right?

IMG_3446.jpeg (1.83 MiB) Viewed 10463 times

IMG_3449.jpeg (1.79 MiB) Viewed 10463 times

[AngryCockroach]

Ok, I found the issue:
The linked guide on geekhack is wrong: Wire 2 and Wire 3 need to be each one pin above!

Here is how you connect the keyboard to the Teensy:

Screenshot_2024-05-14 13.11.28_99s014.jpeg (1.37 MiB) Viewed 10388 times

[AngryCockroach]

I had some duplicate outputs which I fixed with debounce 2 (instead of 1) in the config.

[flowerlandfilms]

Thanks for the update, about to do mine and this was very helpful.