Ideal chip select pin for DIY Arduboy schematic

Hi all!

I am undertaking the design of an Arduboy using an ATMega32u4, 2.42 inch ssd1309, and a w25q128 memory chip. In turn I have been reading up on the different wiring schematics and pin outs here: (Production Arduboy Schematic)

Checking my schematic (seen below) against the data previously linked I am confident with my wiring despite one pin, that being cart or flash select (FLASH_CS or CART CS).

My question is, which is the ideal pin for chip select if my core objectives are to:

  • Maximize compatibility with games/software currently and moving forward (aka trying to avoid having to code or recompile anything).
  • Have leftover pins for different controller inputs (ie: rotary encoder controls).
  • Burn bootloader then use portable activator to write bin files created using the cart builder resource, without issue.

With a pin selected for chip select I will also seek to confirm the correct bootloader settings prior to burn.

Thank you!!


  • Arduboy FX uses the SDA pin
    *Arduboy mini uses the HWB pin

Any of these will be good but since you’ve already wired HWB to the flash cs in your schematic. I’d say just stick with that. It will allow you to use hardware I2C for other things if you want to.

Awesome! So if I elect to use HWB as flash cs:

My bootloader settings will look like this:

My .bin file download will look like this:

and my card writing settings will look like this:

If I have all of these correct I shouldn’t run into any issues seeing as my screen is 2.42inch oled? Or will I need to recompile games?

Thank you so much!


What url are you using for the cart?

I selected this one as it said Arduboy mini:


That’s the one!

Okay great! So with those bootloader settings, cart downloader (arduboy mini .bin file), and cart flash settings (SSD1309 enabled) I shouldn’t run into any issues?

Seems like the Arduboy mini games list pretty much the entire catalog? I am curious about the process of making a game compatible for the mini or HWB flash compatible. How would I go about recompiling a game to be included in a .bin file download?

Also have just played prince of persia/arabia for the first time, it’s absolutely amazing, huge congrats to yourself @filmote and the others involved!

They look right to me but then again what would I know :slight_smile:

Yes, the cart site was the basis of the cart image that Kevin sent for production.

Thank you! Definitely a team effort. And a labour of love for me.


Okay thank you for your help, I may wait for someone else to chime in in regards to the bootloader settings, etc. before pushing on further with my design.

Could anyone confirm these details are correct?



Sorry to be a pain but would anyone be able to confirm this?

Thanks very much!


Should work? You’re the only one who can know for sure!

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Haha that’s good enough for me! I’ll give it a try, thanks!