This is really great. Will it work on 3178 terminal keyboards, e.g. 6052141 or 5640987 ?Note as-is, as the 3178 keyboard is a Model F, so the connector and number of rows/columns will be different so a new PCB would be needed. The basic principle wouldn't change though, aside from the fact Model F's have a smaller capacitance when the key is up, and more capacitance when the key is down (it's the other way around with the beam spring) and some concerns dfj has raised about Model F's not being manufactured with such tight tolerances in capacitance values across keys with the Model F. I hope to do a Model F controller in the near future, as I have a 122-key terminal and a 84-key PC-AT that would benefit.
No, that explanation was lovely. I'm going to reread that post, your link, and then the rest of the thread a few times to try and understand. I hope you don't mind me bugging you more about this.Heh that's good. I'm a software guy as far as my education goes so a bit of a plebe with electrons too :)
I'm an absolute plebe when it comes to this kinda stuff. Trying to learn though so thanks again!
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As far as I can see there are three ways to get a controller:
Use the schematics/PCB/code released above to make your own, or buy one off somebody who is
Buy an unsoldered/unprogrammed kit of parts from me and do it yourself (~$27 USD + shipping)
Buy a fully-assembled/programmed/tested controller from me (~$50 USD + shipping)
First option would be the most fun and fastest if you are buying parts and PCBs locally.
Second option is also fun but you might be able to get the bits cheaper (I'm in New Zealand) if you take the first option. You also have to wait for it to be shipped from NZ, which might be a couple of weeks.
Third option gets you something that works (and has been tested on either my 5251 or 3727). It costs a bit more as I'm no pick-and-place machine and I'd really want to test it properly before shipping it out.
Cost breakdown is as follows.
The PCB cost is $USD9.12 from OSH Park. My cost for components is $NZD21.714 (see below), which is rougly $USD17.
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The remaining $USD23 for me to assemble and program/test the board is pretty conservative. I've no particular desire to make a profit on any of this (I don't think there's much of a market for this niche-in-a-niche), and would prefer that as many people as possible with beamsprings had the opportunity to use them (hence open-source), however I can't give my time away entirely.
This controller will all be a bit more compelling in a few weeks when I've had enough time to write a more user-friendly graphical remapping/diagnostic program. If people do want either option 2 or 3 from me, let me know either on here or through my email, tom@cornall.co.
To make a module that was easier to install, but still let a pcb underneath handle the scan is roughly what other folks are looking at.yah that's kind of my feeling on the way forward too. the problem is that it's so damned hard to make new cases and pcbs for a true F style sense circuit that it's almost practically impossible. to get it to work on a DIY or hobby basis you'd have to require so much weird stuff from the user that it wouldn't be feasible...
BUT we have to be able to hand-build arbitrarily sized M-designs imo before we (meaning ron, the sskr team, wcass, etc.) can really bite into a modernized F.
Now have a flat-mounting method which will fit inside 3278s without needing an adapter board or an unobtainable 90° connector. Ugly but effective. Next job is a controller for Displaywriters.
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Are they actual beamspring Displaywriters or the wee Model F 3178s which had the same layout? Model F controller will necessarily have to be a bit different.
Also, along with my Model F USB controller, I'm about to order a new board, that is a Beamspring Displaywriter controller.
Top:Show Image(http://uploads.oshpark.com/uploads/project/top_image/KcxYPs3y/i.png)
Bottom:Show Image(http://uploads.oshpark.com/uploads/project/bottom_image/KcxYPs3y/i.png)
Slightly awkward layout with the DAC and drain reference in the middle, fanning out to the two sets of row sense circuitry on the far left and right of the board. Not ideal, but IBM must have got away with it (they didn't even have a ground plane!). If there is too much DC bias left to right, I'll have to change the code to scan one set of rows, then set a new Vref through the DAC, before scanning the other set of rows. Hopefully doesn't come to that as obviously would halve the scan rate.
Though I heard Soarer just replaced the controller with a teensy to get his working, the entire controller replacement always struck me as a good solution.
Wow that PCB looks sharp.