Hi all, just thought that I would compile some tips and tricks for a Mysterium build that is self-sourced (i.e. not a kit but ordering each component individually).

I got my PCB printed by JLCPCB, dimensions should automatically update if you did it right, no PCB assembly required as this is a through-hole build.
BOM list (parts list) - check to see if some parts are out of stock, you can then source these parts from different manufacturers. E.g. the 6 pin ISP header was completely out of stock everywhere so I just bought another 6pin header with the exact same dimensions and it worked just fine; the MCU and 10K resistors were also out of stock when I was doing my build so I had to opt for a lesser known manufacturers separately.
Solder EACH part very carefully (esp the components with specific orientations) - I couldn’t get my keyboard to connect for the longest time until I touched up every component’s soldering and figured there was a cold joint somewhere. PRO TIP: even if you have perfect vision, a half decent camera shot on your USB-C soldering will help you identify cold joints way more easily, flux helps a lot too.
Flashing of a blank MCU (hardest step for me) - if you didn’t get your Mysterium from a kit, your MCU (ATMega) is likely blank and you would need to flash it. This was the most difficult step for me as I’m a complete layman to programming and the instructions were vague and daunting. To start, get yourself a SparkFun AVR Pocket Programmer so you don’t have to change any settings. Make sure you get a USB 2.0 to USB mini B as this isn’t included in the kit. Connect the SparkFun 6 pin adapter to your 6pin header on your keyboard after you’ve soldered everything. The orientation matters so if the flash step fails just switch orientation and try again.
Download QMK MSYS, run the initial setup steps. Download Zadig and install usb drivers for your SparkFun programmer (if not you won’t be able to flash), use “Libusb-win32”
Download USBasploader fork from GitHub and use QMK MSYS to navigate to directory by typing cd /c/foldername/ assuming you saved it in c drive and your USBaspLoader folder is foldername
Type make flash, followed by make fuse. Hopefully everything is successful with no errors.
Unplug everything, open QMK Toolbox, put keyboard into bootloader mode by holding BOOT while plugging the USB C in; or plug usb c in and hold boot followed by reset and releasing both. Click the top menu and install drivers and flash the hex file into your keyboard.

Hopefully this helps anyone who might be daunted to start a self sourced Mysterium Build!

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minibois t1_isiy37r wrote on October 16, 2022 at 10:03 AM

I really like these exposed component keebs, looks so good!
Congrats on the nice looking solder job (at least from this side ;) ) and have fun with the keeb!

thelupuss1 t1_isj3lb9 wrote on October 16, 2022 at 11:17 AM

Nice.... Been looking at this as a kit after building a Nibble65, how hard was the USB C socket to solder on? That's my one fear of building this kit...

Thanks.

Lotier t1_iskk0w2 wrote on October 16, 2022 at 6:00 PM

Flux. Use lots of flux. Then just be sure to check your work. Use this if you wanna make the checking easier.

cwon94 OP t1_isj6fne wrote on October 16, 2022 at 11:51 AM

Very nice, coincidentally I’m building SNAP75 from Nullbits as well.. I would say use flux since it helps the solder adhere to the pins more easily! For the small pins you would want to employ drag soldering (i.e. put a bit of solder on the tip of the iron and drag lightly across the tiny pins).

cwon94 OP t1_isj6hvu wrote on October 16, 2022 at 11:52 AM

Difficulty wise, I would say similar!

thelupuss1 t1_isptgbi wrote on October 17, 2022 at 8:16 PM

Thanks for the advice, only problem is now I'm really tempted to get one! 😁

Yornn t1_isjr873 wrote on October 16, 2022 at 2:52 PM

coseyfannitutti did such a great job with those designs and was so kind to leave them all open source.

I recently built a self sourced discipline, and just like you, the flashing of the blank MCU was the more nerve wracking part. I followed this guide with a spare esp8266 I had laying around. Then I had some ArduinoIDE example of an AVRISP over wifi flashed on the esp. Very janky to use avrdude remotely over wifi to flash a blank mcu, but hey, I managed not to brick it.

Dunno if you used flux when soldering your usb-c socket but it helped me tremendously. I bought one of those syringes of thick flux and it made it quite easy.

Also one thing I noticed from the BOM list is that some components were unavailable but only because of the packaging they come in. Some parts come loose and some come on tape (most likely to be use in pick and place machines). On Mouser for example, the same parts in different format have a separate part number. In my case, one of the part was unavailable in the tape form but available as loose parts. So it might be that you dont have to look for an alternate manufacturer, but the same exact part just in a different packaging.

Grats on the build.

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AdditionalSugar3706 t1_istlrk9 wrote on October 18, 2022 at 4:40 PM

This is a very good guide. At the beginning of this year, I also researched it for a long time. What puzzled me was why after I used avrdudess to flash the bootloader hex file into the mcu, I couldn't use qmktoolbox, I must use msys the make flash command.