Tsumara JD21 restoration

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Re: Tsumara JD21 restoration

Post by resistorman »

Neato!
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Re: Tsumara JD21 restoration

Post by Wonks »

Pretty soon you'll be able to mass-manufacture your own reliable version.
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Re: Tsumara JD21 restoration

Post by BJG145 »

I've found my niche, which is asking someone else to rebuild these gadgets rather than trying to do it myself. I can just dream up a fingering chart and a few extra functions and send off an email. Bliss. :D

I've requested this as the default layout, chromatic over two octaves. I think that'll fall under the fingers OK.

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(By the time the manual has been fed through Wayback and Google Translate, it's difficult to find out what the original settings were.)
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Re: Tsumara JD21 restoration

Post by BJG145 »

Wiring the new buttons (and the old pitchbend/modwheel)...

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Re: Tsumara JD21 restoration

Post by Folderol »

Some very pretty soldering there. Well done!
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Re: Tsumara JD21 restoration

Post by BJG145 »

(I can't take the credit; an acquaintance is working on it for me...!)
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Re: Tsumara JD21 restoration

Post by The Elf »

It interests me to know how the microprocessor is being made to handle that number of inputs - I've never figured that part out!
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Re: Tsumara JD21 restoration

Post by BJG145 »

The Elf wrote: Thu Oct 14, 2021 9:42 am It interests me to know how the microprocessor is being made to handle that number of inputs

I'm not sure how this one has been done (I'll ask), though people often use a "button matrix".

https://www.embeddedrelated.com/showarticle/519.php
https://learn.sparkfun.com/tutorials/bu ... -guide/all

This has come together faster than I expected. It's already playable (USB MIDI) together with display and pitchbend.

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Re: Tsumara JD21 restoration

Post by Folderol »

That looks like a nice little display. Where did you get it from?
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Re: Tsumara JD21 restoration

Post by jjlonbass »

The Elf wrote: Thu Oct 14, 2021 9:42 am It interests me to know how the microprocessor is being made to handle that number of inputs - I've never figured that part out!

Most digital systems that feature more than a moderate number of user switches would organise them as a scanned matrix with each switch connecting together a unique combination of row and column.
With this sort of arrangement one could accommodate, for example, 64 switches with an 8 row by 8 column matrix. An explanation of this with a music tech relevant example can be found here. The examples show the columns being driven by microprocessor outputs with the rows as inputs.

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Re: Tsumara JD21 restoration

Post by Folderol »

It's also done for low res analog controls. In the past, I've used HEF4066 to do this.
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Re: Tsumara JD21 restoration

Post by The Elf »

That all looks baffling. One day I need to figure this out to expand the ability of the Arduino toys I make...
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