Adding FX Chip to Homemade Arduboy (Pro Micro)

Hi guys!

Now I want to add an FX Chip (I mean the W25Q128 flash memory).
Which schematics do I have to follow?

go for the lite version. When using a flash chip you’ll also need an OLED CS.

If you can solder a wire to pin 12/ D6 then you can hook that one to OLED CS. If not I recommend to use the two diode and resistor method.

Excuse, I didn’t understand…
Could you explain me better?

My OLED display has already a CS pin (now it’s connected to GND).

You suggested me to use the “lite version”. Do you mean the following picture?


If yes, please, could you tell me where to connect the pins:

RX (or SDA)?

Thank you in advance!

The OLED display and flash chip use the same SPI bus. With OLED CS connected to GND the display always listens to the SPI bus resulting to incorrect behaviour when flash chip is accessed.

Yep, use SDA for flash CS for Arduboy FX compatibility

Flashchip to Pro Micro:

CS  to SDA/PD1 > pin 2
DI  to MOSI    > pin 16
CLK to SCK     > pin 15
DO  to MISO    > pin 14

So you mean that I haven’t to solder any wire on the atmega32u4, right? I mean: I can simply use the pins of the Pro Micro, right?

Some questions:

  1. Do I have to connect both (in parallel) pin “CS” of OLED and pin “CS” of flash chip on pin “D2” of Pro Micro or on “Pin #2” of Pro Micro? They’re different, because “Pin #2” is called “RX1”, while “Pin D2” is the 5th pin on Pro Micro…

  2. On D15 Pro Micro pin I have already connected the OLED pin “SCL”. So you say that I have to connect the pin “CLK” of flash chip “in parallel” to OLED?

  3. On D16 Pro Micro pin I have already connected the OLED pin “SDA”. So you say that I have to connect the pin “DI” of flash chip “in parallel” to OLED?

Thank you!

For the flash chip to work correctly you don’t but for the OLED to function properly you need to for the OLED CS (unless you use the diode/resistor solution)

No only connect Pro Micro to the pin labeled 2 to the flash chip select.



2 questions:

  1. So I have to connect the pin “CS” of flash chip to the second pin of Pro Micro: I mean, to the pin called “RX1”, right?

  2. I still don’t understand where I have to connect the pin “CS” of OLED display…

Thank you.

No the pin labeld 2. That’s the 5th pin:

*Atmega pin D6

The pin D6 of Pro Micro is already connected to “RES” pin of OLED display…so do I have to disconnect it and replace it with the “CS” OLED display pin???

I don’t mean the Arduino digital pin 6 but the Port D6 pin of the atmega32u4. This pin is like the RGB green pin not broken out so you have to solder a wire to it.

@Mr.Blinky means ATmega32u4 pin 26 (PD6), which is assigned to Arduino digital pin 12. This pin is not brought out to a pad on the Pro Micro, so you have to solder directly to ATmega32U4 pin 26.

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Ohhhh!!! Now it’s clear!!! That is not the Port D6…that’s the pin number 26 of atmega32u4, and it’s PD6 - Digital Pin 12!!!

So I didn’t understand what you meant! :grinning:

Yes, yes! Given that @Mr.Blinky talked about “D6” pin, I didn’t understand…! Now it’s clear!!!

@Mr.Blinky @MLXXXp

Anyway, that pin is a bit difficult to solder…so I think I’ll keep the CS pin of OLED connected to GND and I’ll use the “two diodes and resistor” method:


@Mr.Blinky so I have to connect the “SCK” pin of OLED as usual on Pin D15 of Pro Micro, but I don’t understand where I have to connect the “RX” pin (on picture)…

Oh sorry about that! I should update that image.

You shouldn’t connect that diode end to RX but to the Flash chip select pin (in parallel)

So I have to connect it in pin D2 of Pro Micro. Right?

Yes the same pin where you connected the flash chip select to.

@Mr.Blinky @MLXXXp

My last question: with all these modifications (adding the Flash chip and adding “two diodes and resistor” method), will I have problems with .hex games downloaded for Arduboy?

I mean: will I be able to download .hex games and upload them (as is) on my Arduboy clone or will I have to compile the .ino files?

You can use the hex files as with the original Arduboy (FX). You do not need to recompile .ino files.

Some games may have missing sounds though as there is only 1 speaker pin available on the Pro Micro.

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@Mr.Blinky @MLXXXp

First trial failed!!! :smile: :smile: :smile:

I launched:

python C:\1\flashcart-image.bin

then I obtained:

“Found Arduino Leonardo (COM7) at port COM7
Selecting bootloader mode…
Found Arduino Leonardo bootloader (COM8) at port COM8
Opening port …
Bootloader has no flash cart support
Write aborted!”

Which bootloader should I load, and how?