Making the USB-USB Converter

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raoulduke-esq

04 Apr 2021, 15:50

I talked about this in another thread, but wanted to put it here for reference. The instructions/links in TMK/QMK GitHub are a bit dated and contained some worries about clones not working. The instructions on GH for making a Pro Micro version require a 3.3v system, so here’s how to do it with current links to bootleg clone parts that I have verified to work.

Here’s my BOM:

Bootleg Leonardo $13.88
Bootleg USB Host Shield $11.99
Project Box 2-pack $9.49 (optional)
Short USB A Male-to-Female extender I had sitting around (optional)

Here’s my instructions:
1. Order parts
2. Design layouts in QMK while waiting for Amazon to show up
3. Stack Host Shield onto Leonardo
4. Flash. Either of the two reset buttons will work, and QMK Toolbox is my go-to for flashing atmegas.
5. Make a couple notches in the project box for the Leonardo’s USB cable and for the USB extension cable. Leonardo cable goes to the computer and keyboards get plugged into the extension cable. This allows the box to get closed up.
6. Optional - Add a hole in the project box you can stick a paper clip in to hit the reset button. I make sure to add a reset button to all of my layouts so after the initial flash I don’t need the physical button anymore.

At first I wanted to go the Pro Micro route because they’re hella cheap and that’s what I use for everything else, but after I found this I changed my mind. I wasn’t too keen on introducing complexity with 3.3v since all my Pro Micros are 5v/16MHz. I didn’t want to find any under power issues with hungry boards. I also didn’t want to wait 900 years for a mini-shield to be shipped from China.

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Muirium
µ

04 Apr 2021, 17:32

Good to know this works. I may well be tempted. Thanks for the tips. :D

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anthonymak

04 Apr 2021, 18:36

I use a pro micro and a usb mini host shield for one and heak shank the combo. I also use a reed switch as reset.
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Muirium
µ

04 Apr 2021, 18:44

Boss!

headphone_jack

05 Apr 2021, 15:59

Sorry for my idiocy, but what exactly is the point of this? Couldn't you just use a $5 adapter from Amazon if you needed to change I/O?

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raoulduke-esq

05 Apr 2021, 16:13

headphone_jack wrote:
05 Apr 2021, 15:59
Sorry for my idiocy, but what exactly is the point of this? Couldn't you just use a $5 adapter from Amazon if you needed to change I/O?
This makes nearly any USB keyboard work under QMK so you can customize layouts, add layers, add macros, add tap dance keys, etc.

Many production keyboards are interesting but not programmable. The G80-11800, HHKB Pro Classic, and Unicom Space Saver M are some examples from my own collection. With this adapter these boards become as programmable as any custom build.

micmil

05 Apr 2021, 18:28

headphone_jack wrote:
05 Apr 2021, 15:59
Sorry for my idiocy, but what exactly is the point of this? Couldn't you just use a $5 adapter from Amazon if you needed to change I/O?
Yeah, the Teensy/Pro Micro/whatever allows you to load custom firmware. It's not just going from one USB format to another. I know I was confused as hell the first time I saw this idea. :lol: It's a terrible name. "INLINE FIRMWARE ADAPTER" or "AUTOHOTKEY ON A PLATE" may have been better choices. :D

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raoulduke-esq

05 Apr 2021, 19:19

anthonymak wrote:
04 Apr 2021, 18:36
I use a pro micro and a usb mini host shield for one and heak shank the combo. I also use a reed switch as reset.
Cool! Have you encountered any issues from being on 3.3v?

User avatar
anthonymak

05 Apr 2021, 20:01

raoulduke-esq wrote:
05 Apr 2021, 19:19
anthonymak wrote:
04 Apr 2021, 18:36
I use a pro micro and a usb mini host shield for one and heak shank the combo. I also use a reed switch as reset.
Cool! Have you encountered any issues from being on 3.3v?
the pro micro is 5V. I need to replace the regulator to make VCC output 3.3V while the mcu still running at 16Mhz.

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