Pre-Assembled Boards: OLED V2.2 / Mainboard V2.7 / RF Board V3.1 (DIET SANDWICH)

This Version is only available from commercial sellers. Gerbers of this Version have not been published.

Especially Mainboard is now extremely simplified and almost ready. It´s 99% ready, and comes with everything pre-installed, exept:

  • ATMega 328
  • Power Connector
  • Inter PCB-Connections

That is all you need to install, and you´re ready to install Firmware

On Version 2.7 there have been also some component changes, that make the “Sandwich Stack” lower in height -> Diet Sandwich

However, this is just a suggestion, and it can still be stacked in the classical way, which is higher in total, but allows for debugging or exchanging parts in case something goes wrong.

But I want to show you this “DIET” Approach, in case you find it interesting:

Standard Jumper Headers used, ATMega installed without socket. Power Connection cable will be soldered directly to PCB in order to safe some space.

ATTENTION: Watch where I soldered the Header Pins. They are not on the marked side. We´re looking at the PCB from the Bottomside and we can see the shorter side of the Pins, that are usually supposed to go through the PCB. Not in this case. For Diet Sandwich, stick through the longer side of the pins from Bottom Side, and Solder them on top.


OLED IO-Board:


You just need to source and place the THT Components.

Here´s the Schematic for the OLED IO-Board: Schematic_uSDX-IO-OLED_Rev2_1


SW4 (rotary encoder) use EC11B13 (Unlike other rotary encoders, this one is known to work without trouble and comes at a reasonable price)

SW1-SW3 you can use for example these

MK1 (on-Board Mic) for example this one (watch for polarity !!!)

J4,J5,J6 use these

J1 and J2 can be soldered later directly to Mainboard.

J3 is Place Holder for OLED Display, like this one (if you buy another one, watch for the right order of the Pins)

J7 and J8 are Female Pin Sockets, with bent contacts for horizontal mount. Nothing special.

Since it is so easy and you can refor to detailed instructions of older revisions, I´m jumping right to the changed assembly pattern:

Everything installed, exept OLED.

Just pay attention to the microphone you use. It should be lower or maximum as high as the 3,5mm Jacks (around 6mm)

In Order to install OLED-Display lower on PCB, remove electrolytic capacitor C7 and replace it with a 10uF Tantalum Capacitor -> Watch for Polarity !!!

C7 removed
C7 replaced by Tantalum capacitor (Lower Height)
OLED Soldered on Top of that (See Screwholes of OLED -> Soldered to IO Board with Breakaway Headers for added mechanical stability) Position/Height of OLED is now determined by Header Pins, no longer by Capacitor below.

Since we now have such a high level of factory assembly, chances for error are extremely reduced. So I decided, to solder IO Board and Mainboard together to save some space.

PCB´s placed on Top of each other, ready to be soldered.

On picture above I was using washers to set the required height. You can (kind of) see, that the Pins, that go through the Mainboard barely reach the Top Layer at the right distance. So be careful while soldering.

You will have it easier to get the right “Distance” by printing out the Housing (which has built in the right Spacers).

This files contains the STL-Files to 3D-Print and the Gerber Files for Top and Bottom PCB.

The Print Files are absolutely easy to Print. Just Print them lying flat on the Print Bed. They need no supports or rafts.

I was using PETG Filament and 33% Infill. If you use PLA, make sure to Cut Threads before Screwing in the Screws. PLA is more brittle and tends to break easily.

In case of Diet Sandwich, you need 4x M3x20 Screws and 4x M3x10 Screws. The longer ones go on Top, the shorter ones just secure the bottom Cover.

The following Picture basically makes the assembly clear and also where the built in Spacers are:

This Housing is for DIET Stacking only. I will modify and provide that for “Standard Sandwich” later.

The RF Board for this Assembly is 100% as before. No Changes. It still uses the Female Headers to connect to the Mainboard. Can be removed and debugged easily. Can also be exchanged, if we change stuff in the future.

Go to 8-Band Board Page for Assembly Instructions of RF Board.

And here´s a picture of the Diet Sandwich in the Lunchbox.

Ready to eat use: