monic part 3: towards a handheld

[F-73P]

Previous: monic part 2: connecting the keypad

Next: monic part 4: arbitrary-precision rational arithmetic

I will now place the display and matrix keypad on veroboard. The calculator can then be connected to a development board (such as the NXP i.MX RT1010 I have been using so far) via terminal blocks on the left of the veroboard.

I am also trying to find keycaps for the Omron B3F-1052 pushbuttons; any suggestions?

[Maximilian Hohmann]

Hello!

Very interesting project, looking forward to see more of it.

(07-01-2020 01:54 AM)F-73P Wrote:  I am also trying to find keycaps for the Omron B3F-1052 pushbuttons; any suggestions?

I have used this kind for some tinkering projects in the past (this is an eBay-link, unfortunately I couldn't find them anywhere else - they come from China anyway, no matter who you order them from):

https://www.ebay.com/itm/A14-Tactile-Cap...3216076402

You can select a keycap in the colour you like and snap a transparent cover over it. The gap between keycap and cover is large enough for a key label printed on solid/thick paper. These caps should also fit your Omron switches, but better compare the measurements.

Regards
Max

NB: Maybe I missed it in your earlier posts, but what does "monic" stand for?

[Garth Wilson]

(07-01-2020 01:54 AM)F-73P Wrote:  I am also trying to find keycaps for the Omron B3F-1052 pushbuttons; any suggestions?

We use them in a couple of our products at work. Availability has never been a problem at all. See https://www.mouser.com/Electromechanical...ps&FS=True

[Chr Yoko]

Very nice project !
Your chosen microcontroller looks very powerfull , why such choice instead of a 32bits Arduino such as a STM32 base ?

Hereby EEVblog that is showing how to get made a custom membrane keyboard :
https://www.youtube.com/watch?v=H8XBBfvsPj0
From here :
https://www.jrpanel.com/switch/buy/
(exemple @ about US$255 for 4 parts, with embossed keys , their stainless domes and 4 colors on the overlay)



OK, bit expensive and not as good as a real keyboard, but has a professionnal look to it.

Also I would be interrested by the software side of your project ;-)

[F-73P]

Thanks for the suggestions. I've ordered Japanese "Alps Alpine" switches and keycaps, and have started making some keypad labels.

(07-28-2020 09:21 PM)Chr Yoko Wrote:  Your chosen microcontroller looks very powerfull , why such choice instead of a 32bits Arduino such as a STM32 base ?

The i.MX RT EVK boards offer speed and large memories, and the IDE is free and supports programming in C and assembly.

(07-28-2020 09:21 PM)Chr Yoko Wrote:  Hereby EEVblog that is showing how to get made a custom membrane keyboard :
https://www.youtube.com/watch?v=H8XBBfvsPj0
From here :
https://www.jrpanel.com/switch/buy/
(exemple @ about US$255 for 4 parts, with embossed keys , their stainless domes and 4 colors on the overlay)
OK, bit expensive and not as good as a real keyboard, but has a professionnal look to it.

Thanks for the links, they look great. Definitely something to keep in mind for the future.

[F-73P]

Handheld prototype 1.0 is finished.

Schematics:



Soldering the wires, buttons and connectors to the veroboard:



Attaching the display and spacers:



Connecting the microcontroller:



The shift functions:



The final result:

[F-73P]

Recently I bought an MIMXRT1160-EVK development board and 5.5" display. All going well I'll use these to make a second prototype featuring a QWERTY keypad.

[Chr Yoko]

Brilliant ! Thanks to keep us informed !

Maybe you want to create a kind of Sharp PC G850VS ?
(Basic ; C ; Z80)

[F-73P]

(09-12-2022 11:51 AM)Chr Yoko Wrote:  Brilliant ! Thanks to keep us informed !

Maybe you want to create a kind of Sharp PC G850VS ?
(Basic ; C ; Z80)

Thanks, yes something similar: