MegaPocket

MegaPocket is the third in my series of DIY handheld gaming devices that share the same form factor. Powered by an ATmega32U4, it's your basic "big screen" Arduboy® game compatible handheld. The 12V boost circuit needed to drive the 2.42 inch OLED has been incorporated on the PCB.

I spent an age trying to find a case style that I liked, but finally settled for some retro stripes. It's looks a little 70's to me. Apart from expecting the paper thin screen to snap at any point, it was easy enough to put together. Some small RGB LED light bleed issues persist, but I'm happy with the results.

I have no idea what the battery life is like, but it will play all the games that were designed for Arduboy®.

In a break from the other Pocket write-ups, I'm only listing parts I got from AliExpress and Amazon. Everything else came from LCSC Electronics. The BOM file is on the GitHub page for this project.

Licensing: My PCB files and STLs are released under The Unlicense. Everything else retains the licenses assigned by their creators. I take no responsibility for anything.

Arduboy® is a registered trademark of Arduboy, Inc. This project is not affiliated with, authorised by, endorsed by, or connected to Arduboy, Inc. in any way.

I sourced everything (except the case and PCB) from AliExpress, Amazon and LCSC Electronics. Rather than list everything from LCSC, those parts are in the BOM (bill of materials) that can be ordered, if needed, in one go. Everything is in stock currently, although a few parts are low stock. I would not get an ATmega32u4 from Aliexpress. Fakes chips are out there.

The cases were 3d printed in PLA, although I did try a clear resin-printed back by a Chinese manufacturer. Case printing instructions mirror those of previous Pockets.

1 x 2.42 Inch 128x64 OLED Display Module SSD1309 SPI interface White AliExpress

1 x 602550 Polymer Lithium Battery AliExpress

1 x Piezoelectric Piezo Ceramic Wafer 18mm AliExpress

1 x W25Q128FVSG 128Mb/16MB flash chip AliExpress

2 x 0603 LEDs 2 Colours AliExpress

1 x Silicone Rubber Sheet Thickness 0.5 AliExpress

2 x M2 x 16mm Flat Head Hex Socket Screws Amazon

1 x Clear Grass Trimmer Line Amazon

A long list of parts from LCSC Electronics (SEE BOM File!)

Hand Tools & Equipment

Soldering iron + Solder Wire 40/60 + Solder Flux + Isopropyl

A Hot Plate & 3dprinter

Watch Makers Loupe or other Magnification

Kapton tape + Sand Paper + Double Sided Tape

Design files like the STL's, gerbers, schematic, etc. can be found on the GitHub Page for this project

The custom PCB can be ordered from a PCB fabrication manufacturer Like JLBPCB : Gerber File Zip (Use default PCB board settings. 1.6mm thickness etc. Just upload the gerber zip and order)

I started with the hotplate soldered components. I prefer hand soldering, so tend to do the minimum with a hotplate. I did the ATmega32u4, the screen connector, TP4056, 16Mhz crystal and Texas Instruments high voltage boost converter at U1.

Bridging issues are going to be very common between the OLED connector pins and the ATmega32u4 pins. Lots of inspection and solder reworking is usually needed.

Once these are done, everything else on the back can be hand soldered. Loads of components need to be the right way around to function.

Applying too much heat to the on/off switch will render it useless. Also getting too much isopropanol in any of the buttons will make them unreliable or stop working completely.

When attaching the battery,make sure the polarity is correct! Some batches of batteries will have the red (positive) and black (negative) wires swapped around. A bit of double-sided tape was used to fix the 600mAh 602550 battery.

I would not bother fixing the screen on at this point, since the ATmega32U4 needs to be programmed first. See Step 2

The ATmega32U4 needs the Arduboy® FX bootloader. Unfortunately, this can't be done via the USB port, and needs an external programmer.

I used an UNO and connected it to the PCB.

I haven't bothered with any kind of wire color convention. Also in the image, the black wire (VCC - lol) is in the 3.3v on the UNO and should be in 5v.

The following guide excerpt has been lifted from https://www.hackster.io/nod3011/arduboy-diy-with-fx-cca276 (a great project by Manoch Teachajareonvikul)

...grab Arduino IDE version 1.8.19

direct link: https://downloads.arduino.cc/arduino-1.8.19-windows.zip

install MrBlinky Arduboy-homemade-package

link: GitHub - MrBlinky/Arduboy-homemade-package: Arduino IDE board package for Arduboy and homemade versions making things easy

* instruction are in his Github

5. Go to File>Examples>ArduinoISP>ArduinoISP Open it. Then plug Arduino UNO with PC/mac then upload the code to make Arduino UNO as ISP

Burn bootloader with setting like picture above. Make sure that you connect Arduino Pro Micro with Arduino UNO

Make sure the right port is selected, click on Burn Bootloader and wait for result. If there are no errors, the ATmega32U4 now has the Cathy3K Arduboy® bootloader and you can remove the wires from the PCB.

If you get errors ... check your wiring (although it could be anything)

I bought a few 2.42 inch OLED boards from AliExpress. Since I only want the raw screen it has to be remove from the PCB. Bend the four metal tab to remove the metal surround. The screen is further attached with two smallish black double sided sticky tabs. I uses a craft bladed dipped inisopropanol to cut through them. Take it slow... aaaand it's ruined. Actually, miraculously I didn't break any of them.

The remaining black tape comes off easy enough with isopropanol.

I didn't use a fancy mounting method when attaching the screen to the PCB. It's just two 3mm high sticky foam squares, which I repositioned for 20 minutes until the screen was in the right position for the case. There are markings on the PCB that help, and getting the horizontal alignment is easy. Vertical... not so much

The PLA case, light pipes, silicone sheet, and screws have all been covered in my other projects : PicoPocket & CrokPocket. It's all exactly the same since they are part of set.

One tiny difference is a little extra has to be cut out of the siicone sheet (see image)

The piezoelectric speaker is hot-glued to the rear case housing before being soldered to the PCB

Once everything is together, you can upload games to the flash chip. The MegaPocket needs to be turned on and plugged into your computer. I used the Arduboy Toolset 0.7.1 (Github link).

You will need some games in the form of a BIN file, which I got from https://www.bloggingadeadhorse.com/cart/CartBuilder.html

Make sure the SSD1309 screen patch is selected and then upload your games to the flash chip on the MegaPocket

Conclusion

MegaPocket is based on various schematics and guesswork. It's amateurish, but works and looks okay, which are really my only criteria. This could be the last in my "Pocket" range, although there is room for further expansion one day.

I built this gadget for myself. The BOM file is wild, and mistakes may be present. I haven't come across issues with it's function though.

There is a short 5 minute video about MegaPocket on my YouTube channel.

Check out https://www.arduboy.com for Arduboy® products. There was a rumor that there might be an official 2.42 inch screened Arduboy® one day....