USB keyboard interface for Minstrel 4th

USB keyboard interface for Minstrel 4th - Prototype to PCB

oday we transfomed this magnificent mess of wires....

Into this beautiful little module

It plugs into the Minstrel 4th's RC2014 port, either directly, or as here, using an RC2014 backplane. It accepts a USB keyboard* via an OTG adaptor (USB A to micro).

Like its inspiration, the Jupiter Ace, you wouldn't want to spend serious typing time on the Minstrel's tactile keyboard. It's nice to have a familiar layout of full-size keys, and the interface's firmware buffers your input, meaning that you can type as fast as you like.

It took a lot of development time to get to a working breadboard prototype. It's pretty fragile and so it feels very good to have received the first PCBs today.

There was a minor hitch, which has to do with my limited understanding of the Pico's confusing VBUS/VSYS power supply circuit. In the end it was easily solved with a solder bridge and here it is working:

Since ordering these version 1 boards, I decided to add the ability to connect to the interface using a Terminal on a modern computer, meaning that you can type via the terminal app and have a 'paper tape' record of your work, either by copying and pasting from the terminal or using a capture file. You can then re-paste word definitions or longer listings into the terminal. I think I'll find this more convenient than saving and loading**. Here's a quick demo:

With the minor correction made, and FTDI header added to the PCB design, version 1.1 is ordered, along with components to make the first batch.

I'm now selling this item: the listing's url changes over time as I make and sell batches, so please contact me at: shirley at newstuffforoldstuff dot com for details

* not all keyboards are supported. I still haven't found out what factor determines whether a keyboard works with the TinyUSB Pico library, all I can say is that some do, some don't.

** this has the added benefit that you can compile and paste a 'clean' listing of your tested word definitions. I've found EDIT, REDEFINE and FORGET problematic with Ace Forth.

Comments

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