Author Topic: IBM Model F 5291 Terminal (bigfoot) Keyboard  (Read 17367 times)

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Offline xavierblak

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IBM Model F 5291 Terminal (bigfoot) Keyboard
« on: Tue, 24 September 2013, 11:50:03 »
I fear this may be a bit of a lost cause but it's worth a shot. I recently acquired a handful of vintage keyboards. They're a little dirty and all the cords have been removed by someone looking for some scrap copper.

One of those keyboards was what I assumed to just be a Model F XT/AT board. But while cleaning it I opened it up and noticed it had too many wires to just be connected to a din connector. After a little searching it looks like I have a IBM 5291 Keyboard.

Anyone ever seen an adapter for one of these keyboards? Anyone have info on the pinout/protocol used to connect this to whatever terminal it was originally connected too?

Edit:
Just adding a link to some nice pics of the this model keyboard. Still googling for a protocol or pin out.

Controller firmware is now up, and handles this keyboard :D
« Last Edit: Mon, 04 November 2013, 08:09:36 by xavierblak »

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #1 on: Tue, 24 September 2013, 16:48:16 »
Soarer told me his converter can't be used to convert this kind of Model F, but I'm really hoping someone on geekhack manages to do it in a reasonably easy fashion and posts his results. I really love the legs on this keyboard.
Most of the modding can be done on your own once you break through the psychological barriers.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #2 on: Tue, 24 September 2013, 16:48:44 »


It has no CPU! The 'protocol' as such is driving the mux and capacitive sense chips directly. I've got proof-of-concept code working pretty well, but it needs more work.

In essence, to read a key...
  • set the key code onto the D lines
  • set strobe low
  • delay for a microsecond or two
  • read the output
  • set strobe high

On the plus side, it uses the older 4-channel capsense chip which seems to be far easier to drive than the 8-channel version with its variable sensitivty setting. I've been scanning the matrix at 1000Hz :D
« Last Edit: Wed, 25 September 2013, 05:30:06 by Soarer »

Offline 0100010

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #3 on: Tue, 24 September 2013, 21:22:44 »
Got any pics of the controller board - if it has one?

Wondering if it is like the 104 key Unsaver F's, where swapping in a 122 key F control board works to make it compatible.
  Quoting me causes a posting error that you need to ignore.

Offline xavierblak

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #4 on: Wed, 25 September 2013, 00:40:12 »
Show Image


It has no CPU! The 'protocol' as such is driving the mux and capacitive sense chips directly. I've got proof-of-concept code working pretty well, but it needs more work.

In essence, to read a key...
  • set the key code onto the D lines
  • set strobe low
  • read the output
  • set strobe high

On the plus side, it uses the older 4-channel capsense chip which seems to be far easier to drive than the 8-channel version with its variable sensitivty setting. I've been scanning the matrix at 1000Hz :D

Hmm I think I follow. So I'm picking the key I want to know the status of with the D lines and then setting strobe low to get the state on the out pin? Cool, thanks for the info. Any chance you have the pinout from the pcb? I don't have the 15 pin connector anymore since my cable was removed before I bought it.


Got any pics of the controller board - if it has one?

I didn't but I just took some.

It's hard to say for sure unless I take the keyboard section apart but the pcb seems to continue down below the keys and is actually what registers the key contacts in place of the typical flexible membrane.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #5 on: Wed, 25 September 2013, 05:27:40 »
From 5291_MaintenanceLibrary.pdf p38:

36759-0



In a useful format, that's:

Code: [Select]
           D1  1      20  Ground
(missing pin)             -Strobe
           D2             Ground
           D3             D0
     (unused)             (unused)
     (unused)             (unused)
     (unused)             Frame Ground
           D4             +5V
           D5             Ground
           D6  10     11  Output

Only one Ground pin needs to be connected, I used pin 12.
« Last Edit: Wed, 25 September 2013, 05:35:55 by Soarer »

Offline poxeclipse

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #6 on: Wed, 25 September 2013, 05:29:28 »
They look and feel better without the casing. Soarer, will try your controller  when is ready.
« Last Edit: Fri, 27 September 2013, 07:53:19 by poxeclipse »

Offline xavierblak

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #7 on: Wed, 25 September 2013, 08:23:56 »
In a useful format, that's:

Code: [Select]
           D1  1      20  Ground
(missing pin)             -Strobe
           D2             Ground
           D3             D0
     (unused)             (unused)
     (unused)             (unused)
     (unused)             Frame Ground
           D4             +5V
           D5             Ground
           D6  10     11  Output

Awesome! Is the code you mentioned earlier available to look at?

Thanks so much for you knowledge on this stuff. I didn't think I'd get so much good info, glad you could prove me wrong.  :thumb:

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #8 on: Thu, 26 September 2013, 05:07:30 »
Source code isn't available. I'm actually using my generic controller code, which I keep saying will be available 'soon', but I've had some interesting Real Work recently taking my time! It takes a config file to set it up, for this 'board it looks like:

Code: [Select]
matrix
scanrate 1
debounce 1
blocking 0
muxstrobe_port PB6:0
sense_delay 1
muxstrobe_gate -PD1
sense_polarity 1

sense PD0

muxstrobe 0 UNASSIGNED
muxstrobe 1 UNASSIGNED
muxstrobe 2 UNASSIGNED
# ...
muxstrobe 94 UNASSIGNED
muxstrobe 95 UNASSIGNED
end

Offline xavierblak

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #9 on: Fri, 27 September 2013, 02:14:51 »
Status update. I've got a proof of concept up and running. Thanks so much Soarer!

Next step map the key layout.

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #10 on: Fri, 27 September 2013, 23:53:35 »
erm, I'm not really following this, but can I ask if there is a very high chance of this keyboard being adapted to work on a soarer converter?

I have gotten me some colored dupont line connectors and a teensy with legs and breadboard. Once xavierblak gets his F terminal up and running, I had better buy one before ebay prices soar through the roof.
Most of the modding can be done on your own once you break through the psychological barriers.

Offline poxeclipse

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #11 on: Sat, 28 September 2013, 07:38:14 »
I have two of these keyboards. Willing to test a new controller, when it is ready.
« Last Edit: Sat, 28 September 2013, 20:10:58 by poxeclipse »

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #12 on: Sat, 28 September 2013, 19:39:44 »
These jumper wires are great for quickly hacking a Teensy inside most IBMs...

37250-0

Offline xavierblak

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #13 on: Sun, 29 September 2013, 01:05:28 »
erm, I'm not really following this, but can I ask if there is a very high chance of this keyboard being adapted to work on a soarer converter?

That would be up to soarer as I don't believe he's released the source for this controller. Either way I'm just using a teensy connected to the circuit board. I'll have to look at some of the avaiable teensy firmwares to see if any of them make sense to be converted to work with this keyboard. Once I have something working I'll post it here.

I have two of these keyboards. Willing to test a new controller, when it is ready.

I'll post to this thread once I have something. Do you have a Teensy and the ability to connect it to your keyboards?

These jumper wires are great for quickly hacking a Teensy inside most IBMs...

(Attachment Link)

I probably should have though of this but I still had a small pigtail of the wire left inside the case. So I just solder this to a perfboard with a dip socket for the teensy.

Offline poxeclipse

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #14 on: Sun, 29 September 2013, 07:53:10 »

I have two of these keyboards. Willing to test a new controller, when it is ready.

I'll post to this thread once I have something. Do you have a Teensy and the ability to connect it to your keyboards?
Yes, I do. 
« Last Edit: Wed, 06 November 2013, 03:10:26 by poxeclipse »

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #15 on: Sun, 29 September 2013, 13:25:17 »
Soarer, I know every post I make demonstrates my ignorance, but how did you connect the jumper cables directly to the PCB? Unless there are already connectors there which happen to be hidden by the dupont connectors' heads?

These jumper wires are great for quickly hacking a Teensy inside most IBMs...

(Attachment Link)
Most of the modding can be done on your own once you break through the psychological barriers.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #16 on: Sun, 29 September 2013, 15:33:05 »
There's a connector there that looks like two rows of Teensy pins side-by-side. It's where the cable would normally plug in to the PCB.

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #17 on: Mon, 30 September 2013, 07:59:58 »
Um soarer, so are you able to make that keyboard work like a normal keyboard? Or are we at the physical-connection stage still? I am following this with great interest.

There's a connector there that looks like two rows of Teensy pins side-by-side. It's where the cable would normally plug in to the PCB.
Most of the modding can be done on your own once you break through the psychological barriers.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #18 on: Mon, 30 September 2013, 20:34:21 »
I guess you could call this 'working like a normal keyboard' - I just put a basic keymap onto it and typed this :D

Code: [Select]
matrix
scanrate 1
debounce 1
blocking 0
muxstrobe_port PB6:0
sense_delay 1
muxstrobe_gate -PD1
sense_polarity 1

sense PD0

muxstrobe  0 Z # 00
muxstrobe  1 S # 01
muxstrobe  2 W # 02
muxstrobe  3 3 # 03
muxstrobe  4 X # 04
muxstrobe  5 D # 05
muxstrobe  6 E # 06
muxstrobe  7 4 # 07
muxstrobe  8 C # 08
muxstrobe  9 F # 09
muxstrobe 10 R # 0A
muxstrobe 11 5 # 0B
muxstrobe 12 V # 0C
muxstrobe 13 G # 0D
muxstrobe 14 T # 0E
muxstrobe 15 6 # 0F
muxstrobe 16 B # 10
muxstrobe 17 H # 11
muxstrobe 18 Y # 12
muxstrobe 19 7 # 13
muxstrobe 20 N # 14
muxstrobe 21 J # 15
muxstrobe 22 U # 16
muxstrobe 23 8 # 17
muxstrobe 24 PAD_2 # 18
muxstrobe 25 PAD_5 # 19
muxstrobe 26 PAD_8 # 1A
muxstrobe 27 NUM_LOCK # 1B
muxstrobe 28 M # 1C
muxstrobe 29 K # 1D
muxstrobe 30 I # 1E
muxstrobe 31 9 # 1F
muxstrobe 32 COMMA # 20
muxstrobe 33 L # 21
muxstrobe 34 O # 22
muxstrobe 35 0 # 23
muxstrobe 36 PERIOD # 24
muxstrobe 37 SEMICOLON # 25
muxstrobe 38 P # 26
muxstrobe 39 MINUS # 27
muxstrobe 40 SLASH # 28
muxstrobe 41 QUOTE # 29
muxstrobe 42 LEFT_BRACE # 2A
muxstrobe 43 EQUAL # 2B
muxstrobe 44 SPACE # 2C
muxstrobe 45 RSHIFT # 2D
muxstrobe 46 BACKSLASH # 2E              # ~ (ISO)
muxstrobe 47 RIGHT_BRACE # 2F
muxstrobe 48 CAPS_LOCK # 30
muxstrobe 49 PAD_ASTERIX # 31
muxstrobe 50 ENTER # 32
muxstrobe 51 BACKSPACE # 33
muxstrobe 52 PAD_0 # 34
muxstrobe 53 PAD_1 # 35
muxstrobe 54 PAD_4 # 36
muxstrobe 55 PAD_7 # 37
muxstrobe 56 PAD_PLUS # 38
muxstrobe 57 UNASSIGNED # 39
muxstrobe 58 PAD_MINUS # 3A
muxstrobe 59 SCROLL_LOCK # 3B
muxstrobe 60 PAD_PERIOD # 3C
muxstrobe 61 PAD_3 # 3D
muxstrobe 62 PAD_6 # 3E
muxstrobe 63 PAD_9 # 3F
muxstrobe 64 EUROPE_2 # 40             \ | (ISO)
muxstrobe 65 A # 41
muxstrobe 66 Q # 42
muxstrobe 67 2 # 43
muxstrobe 68 LALT # 44
muxstrobe 69 UNASSIGNED # 45
muxstrobe 70 UNASSIGNED # 46
muxstrobe 71 1 # 47
muxstrobe 72 F7 # 48
muxstrobe 73 F5 # 49
muxstrobe 74 F3 # 4A
muxstrobe 75 F1 # 4B
muxstrobe 76 F8 # 4C
muxstrobe 77 F6 # 4D
muxstrobe 78 F4 # 4E
muxstrobe 79 F2 # 4F
muxstrobe 80 F10 # 50
muxstrobe 81 UNASSIGNED # 51
muxstrobe 82 UNASSIGNED # 52
muxstrobe 83 UNASSIGNED # 53
muxstrobe 84 F9 # 54
muxstrobe 85 UNASSIGNED # 55
muxstrobe 86 UNASSIGNED # 56
muxstrobe 87 UNASSIGNED # 57
muxstrobe 88 LSHIFT # 58
muxstrobe 89 LCTRL # 59
muxstrobe 90 TAB # 5A
muxstrobe 91 ESC # 5B
muxstrobe 92 UNASSIGNED # 5C
muxstrobe 93 UNASSIGNED # 5D
muxstrobe 94 UNASSIGNED # 5E
muxstrobe 95 UNASSIGNED # 5F
end

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #19 on: Tue, 01 October 2013, 00:18:45 »
Hey Soarer,

That's awesome, but where did you type the stuff? Is the following text be put into an .sc file like your standard remapblock? I notice you have 13 unassigned keys. Does that mean the PCB has 13 spare contacts lurking inside the casing, or are they merely the additional f13-24 that I notice this keyboard has sharing keycaps with f1-12?

Well if you've managed to make it work, I guess the next question is whether it is practical and usable for normal purposes.

Are there any power requirements that make the keyboard impractical to use on a standard USB connection to a desktop?

Looking on ebay, these guys arent cheap. Considering how much more troublesome they are than an F XT and still share the same infuriating layout, it's ridiculous.

I guess you could call this 'working like a normal keyboard' - I just put a basic keymap onto it and typed this :D

Code: [Select]
matrix
scanrate 1
debounce 1
blocking 0
muxstrobe_port PB6:0
sense_delay 1
muxstrobe_gate -PD1
sense_polarity 1

sense PD0

muxstrobe  0 Z # 00
muxstrobe  1 S # 01
muxstrobe  2 W # 02
muxstrobe  3 3 # 03
muxstrobe  4 X # 04
muxstrobe  5 D # 05
muxstrobe  6 E # 06
muxstrobe  7 4 # 07
muxstrobe  8 C # 08
muxstrobe  9 F # 09
muxstrobe 10 R # 0A
muxstrobe 11 5 # 0B
muxstrobe 12 V # 0C
muxstrobe 13 G # 0D
muxstrobe 14 T # 0E
muxstrobe 15 6 # 0F
muxstrobe 16 B # 10
muxstrobe 17 H # 11
muxstrobe 18 Y # 12
muxstrobe 19 7 # 13
muxstrobe 20 N # 14
muxstrobe 21 J # 15
muxstrobe 22 U # 16
muxstrobe 23 8 # 17
muxstrobe 24 PAD_2 # 18
muxstrobe 25 PAD_5 # 19
muxstrobe 26 PAD_8 # 1A
muxstrobe 27 NUM_LOCK # 1B
muxstrobe 28 M # 1C
muxstrobe 29 K # 1D
muxstrobe 30 I # 1E
muxstrobe 31 9 # 1F
muxstrobe 32 COMMA # 20
muxstrobe 33 L # 21
muxstrobe 34 O # 22
muxstrobe 35 0 # 23
muxstrobe 36 PERIOD # 24
muxstrobe 37 SEMICOLON # 25
muxstrobe 38 P # 26
muxstrobe 39 MINUS # 27
muxstrobe 40 SLASH # 28
muxstrobe 41 QUOTE # 29
muxstrobe 42 LEFT_BRACE # 2A
muxstrobe 43 EQUAL # 2B
muxstrobe 44 SPACE # 2C
muxstrobe 45 RSHIFT # 2D
muxstrobe 46 BACKSLASH # 2E              # ~ (ISO)
muxstrobe 47 RIGHT_BRACE # 2F
muxstrobe 48 CAPS_LOCK # 30
muxstrobe 49 PAD_ASTERIX # 31
muxstrobe 50 ENTER # 32
muxstrobe 51 BACKSPACE # 33
muxstrobe 52 PAD_0 # 34
muxstrobe 53 PAD_1 # 35
muxstrobe 54 PAD_4 # 36
muxstrobe 55 PAD_7 # 37
muxstrobe 56 PAD_PLUS # 38
muxstrobe 57 UNASSIGNED # 39
muxstrobe 58 PAD_MINUS # 3A
muxstrobe 59 SCROLL_LOCK # 3B
muxstrobe 60 PAD_PERIOD # 3C
muxstrobe 61 PAD_3 # 3D
muxstrobe 62 PAD_6 # 3E
muxstrobe 63 PAD_9 # 3F
muxstrobe 64 EUROPE_2 # 40             \ | (ISO)
muxstrobe 65 A # 41
muxstrobe 66 Q # 42
muxstrobe 67 2 # 43
muxstrobe 68 LALT # 44
muxstrobe 69 UNASSIGNED # 45
muxstrobe 70 UNASSIGNED # 46
muxstrobe 71 1 # 47
muxstrobe 72 F7 # 48
muxstrobe 73 F5 # 49
muxstrobe 74 F3 # 4A
muxstrobe 75 F1 # 4B
muxstrobe 76 F8 # 4C
muxstrobe 77 F6 # 4D
muxstrobe 78 F4 # 4E
muxstrobe 79 F2 # 4F
muxstrobe 80 F10 # 50
muxstrobe 81 UNASSIGNED # 51
muxstrobe 82 UNASSIGNED # 52
muxstrobe 83 UNASSIGNED # 53
muxstrobe 84 F9 # 54
muxstrobe 85 UNASSIGNED # 55
muxstrobe 86 UNASSIGNED # 56
muxstrobe 87 UNASSIGNED # 57
muxstrobe 88 LSHIFT # 58
muxstrobe 89 LCTRL # 59
muxstrobe 90 TAB # 5A
muxstrobe 91 ESC # 5B
muxstrobe 92 UNASSIGNED # 5C
muxstrobe 93 UNASSIGNED # 5D
muxstrobe 94 UNASSIGNED # 5E
muxstrobe 95 UNASSIGNED # 5F
end
Most of the modding can be done on your own once you break through the psychological barriers.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #20 on: Tue, 01 October 2013, 06:59:56 »
Yeah, my controller code takes a config file, like my converter. I think I'm about ready to release a second beta test of it - but be warned, it will come with _very_ scant documentation!

I haven't used for long stretches, but I haven't seen any glitches like missing or doubled key-presses, even with an armful of keys pressed. It takes less power than a PC/XT keyboard, since it has no CPU.

I haven't taken it apart to look (I'm sure there's a pic out there somewhere) but I don't think there are any other usable pads. 5 of the gaps are used to read the jumper settings. Anything to do with the key markings would've been handled by the terminal, so I've no idea what the 1-12 / 13-24 markings are or how they functioned. I just put PC/XT codes on, as a familiar base for adding remaps and layers to later.

I guess there's no particular reason for anyone to get one of these unless the faster scanning is important to them.
« Last Edit: Tue, 01 October 2013, 07:04:20 by Soarer »

Offline berserkfan

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #21 on: Tue, 01 October 2013, 07:46:52 »
I await the good news! (And in the meantime, I still have Model F on my ebay radar screen...)  :thumb:

Most of the modding can be done on your own once you break through the psychological barriers.

Offline Soarer

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #22 on: Mon, 04 November 2013, 06:57:42 »
Controller firmware is now up, and handles this keyboard :D

Offline poxeclipse

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #23 on: Tue, 05 November 2013, 12:51:17 »
Controller firmware is now up, and handles this keyboard :D


Did somebody try it on 3178 display terminal keyboards ?
« Last Edit: Wed, 06 November 2013, 02:58:32 by poxeclipse »

Offline xavierblak

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #24 on: Wed, 06 November 2013, 21:09:51 »
I probably won't be able to get any photos up for a while. But I got it all cleaned up and am typing on it right now. Thanks to Soarer for posting his firmware. :)

With it's legs fully extended this thing is a monster!!!!

Offline Soarer

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #25 on: Thu, 07 November 2013, 06:38:17 »
Controller firmware is now up, and handles this keyboard :D


Did somebody try it on 3178 display terminal keyboards ?

I doubt it, yet!

edit: moved full reply to my controller thread  ;D
« Last Edit: Thu, 07 November 2013, 06:43:48 by Soarer »

Offline poxeclipse

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #26 on: Thu, 07 November 2013, 07:01:48 »
Controller firmware is now up, and handles this keyboard :D


Did somebody try it on 3178 display terminal keyboards ?

I doubt it, yet!

edit: moved full reply to my controller thread  ;D


They do have a chip, it's not the same as 5291, right ?

Offline poxeclipse

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #27 on: Thu, 07 November 2013, 07:02:32 »
I probably won't be able to get any photos up for a while. But I got it all cleaned up and am typing on it right now. Thanks to Soarer for posting his firmware. :)

With it's legs fully extended this thing is a monster!!!!

Try without the case. It's much easier to type.

Offline Soarer

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #28 on: Thu, 07 November 2013, 07:19:39 »
Controller firmware is now up, and handles this keyboard :D


Did somebody try it on 3178 display terminal keyboards ?

I doubt it, yet!

edit: moved full reply to my controller thread  ;D


They do have a chip, it's not the same as 5291, right ?

Not the same. I think they have an 8048 CPU (40-pin chip), but I don't know which capsense chip they have.

Offline SneakyRobb

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #29 on: Tue, 11 February 2014, 11:57:10 »
Hi,

I have 4176191 for 5291.

I used the controller from soarer on teensy 2.0.
Soarer_controller_v1.20_beta4_atmega32u4.hex.54190-0

I used scaswr to upload and hid listen to listen.

The teensy is wired directly to the pcb pins like is shown in a picture earlier in this thread.

My question is, that after all of this is done, the output I see on hid_listen is bizarre.
it consists of masses of data.
I tried with the config 'bigfoot' but when I pressed a key, it would type something like "-.36QE258O.P/"
Or close all my windows, open a window and type randomly, which was seen earlier in thread.

I made simple alterations to soarer config with everything unassigned.
On hid_listen the out put was about 500 characters of the form

"/03 \5E /12" etc. whenever I press a random key.

When nothing is presed on the keyboard nothing seems to happen.
I feel this is likely electrical/wiring.
I have provided a picture of my wiring.

The ground wire is something that might be a concern as I thought it might be necessary.
I do not know about it though and have a novice understanding of all of this.

Regardless, what is my course of action?
Is this a wiring issue or is it a mistake I made in setup

edit: also putting my hand near it seems to be picked up on hid listen?
« Last Edit: Tue, 11 February 2014, 13:51:04 by SneakyRobb »

Offline Soarer

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #30 on: Tue, 11 February 2014, 14:17:37 »
Try replacing the bolt that holds the PCB to the backplate - that makes an important ground connection!

Offline SneakyRobb

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #31 on: Tue, 11 February 2014, 14:30:17 »
Try replacing the bolt that holds the PCB to the backplate - that makes an important ground connection!

This has worked!

Thanks for the quick reply, and writing all of this firmware.


Offline Soarer

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #32 on: Tue, 11 February 2014, 15:31:57 »

Offline SneakyRobb

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #33 on: Wed, 19 February 2014, 11:09:11 »
From 5291_MaintenanceLibrary.pdf p38:

(Attachment Link)

(Attachment Link)

In a useful format, that's:

Code: [Select]
           D1  1      20  Ground
(missing pin)             -Strobe
           D2             Ground
           D3             D0
     (unused)             (unused)
     (unused)             (unused)
     (unused)             Frame Ground
           D4             +5V
           D5             Ground
           D6  10     11  Output

Only one Ground pin needs to be connected, I used pin 12.


Hi,

How does the frame ground work? Is that included in the only need one pin? My keyboard works, I am just having a hard time finding information about grounding.

Offline SneakyRobb

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #34 on: Wed, 19 February 2014, 11:52:54 »
It seems that it shorts out when the steel backplate is in contact with the metal pan. Are not these components supposed to be touching at all times though?

Offline SneakyRobb

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #35 on: Fri, 21 February 2014, 08:57:00 »
I think what is happening is that the lack of tabs and bolt issues. It seems to work if I support it on little feet. There are two nuts on the back that I installed that were coming into contact with the pan. I see now fohat's recommendation about keeping tabs intact.

 I think my issue is not electrical. I think there is not enough stable physical connection between the two plates, meaning that they can move ever so slightly so that if the back one is pressed it actually strains away from the front, giving spurious readings. I do not know if this is conclusive, but given that it was working and I changed nothing except how it was supported that I must be pointed in this direction.
I had rather enthusiastically removed most of the tabs, and the current arrangement allows for the plates to slide apart vertically slightly, I will perhaps need to install more bolts in order to achieve stability as well as proper spacing.


Offline Soarer

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #36 on: Fri, 21 February 2014, 20:35:42 »
Frame ground is intended as a safety precaution - a separate connection from the keyboard case to the host's frame ground. Using USB power provides plenty of protection, so we don't really need more. You could connect it to ground on the Teensy. It being disconnected is highly unlikely to affect the functioning of the keyboard, and nor is the lower frame or bolts touching the case.

So yeah, it sounds more like a mechanical issue. I can't remember how much space there is for making holes in the PCB, but one idea might be to have a couple of bolts tight, using washers in the middle of the sandwich to get the height right. Perhaps there's room at the front edge of the keyboard. That should reduce wobble, but I don't know if it would solve the issue. Disclaimer: I've never bolt modded any BS, so I'm just guessing!

Offline input

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #37 on: Fri, 18 July 2014, 13:37:55 »
Big thanks to soarer and xavierblack, I have had this 5291 for a couple of years and only just stumbled upon this thread.

I never thought I would see the day when I could actually see output from this keyboard, absolutely amazing.

Definitely a strange typing experience, spacebar is so large, feels so much nicer than an model M.

Still going strong after 27 years,
Daily drivers: Filco w/ browns @ home and work (w/ o-rings), Home coding: 1987 IBM Model M + other random keyboarding goodies.

Offline dorkvader

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Re: IBM Model F 5291 Terminal (bigfoot) Keyboard
« Reply #38 on: Fri, 18 July 2014, 16:01:45 »
Big thanks to soarer and xavierblack, I have had this 5291 for a couple of years and only just stumbled upon this thread.

I never thought I would see the day when I could actually see output from this keyboard, absolutely amazing.

Definitely a strange typing experience, spacebar is so large, feels so much nicer than an model M.

Still going strong after 27 years,

you may want to consider lightening up the spacebar a bit if you plan to use it for a while, though. I'm glad you got it working, and it's a great KB to type on.

Offline cohomology

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Re: IBM Model F 5291 Terminal Keyboard
« Reply #39 on: Fri, 23 January 2015, 08:42:03 »
From 5291_MaintenanceLibrary.pdf p38:

(Attachment Link)

(Attachment Link)

In a useful format, that's:

Code: [Select]
           D1  1      20  Ground
(missing pin)             -Strobe
           D2             Ground
           D3             D0
     (unused)             (unused)
     (unused)             (unused)
     (unused)             Frame Ground
           D4             +5V
           D5             Ground
           D6  10     11  Output

Only one Ground pin needs to be connected, I used pin 12.

Forgive my newbie question, I am guessing D0, D1, D2, D3 , D4, D5, D6 etc. are the pins on the teensy, but what about Strobe, Frame GND and Output? Not able to locate these pins on teensy 2.0 board I just picked up. Thanks!