Flash cart(ridge)

Hey, uh …
I think I am definitely late to this. But while I am drawing the PCB myself I found out a (potentially) crucial flaw:
The current flash cart(ridge) connector does not have a CS pin.
So what I did (on my instance) is to use the NC pin, and connect it to D2.

You know, RX and D2 are the same thing :wink:

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The formerly NC pin has been assigned to A5.

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RX is D0 and Tx is D1.
That is, depend on which board you are using as reference.

Initially I agreed upon the idea of a analog input pin, but I feel like a chip select for the breakout SPI is more important.

Any pin can be used as an SPI chip select including A5. The dedicated SPI SS pin is used by the Arduboy for the USB RXLED.

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Okay I now understand that with ‘D2’ you ment digital pin 2.

Note that digital pin 2 is connected to the same pin as SDA ( They are both connected to Port D Bit 1 )

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Sort of. There are multiple ways to call each one of them, depend on which one you are looking at (e.g. from the microcontroller’s pinout perspective or the Arduino’s pin function perspective).

Late reply, but I forgot to ask about the label size.
Hello again!

Here’s a theoretical question: with the new wiring, can you still use I2C?

Both I2C and SPI writes are blocking and can’t happen at the same time, right? So if SCLK is not driven, then whatever happens with CS doesn’t matter, and if SCL is not driven, then the state of SDA doesn’t matter. The only downside is the need to switch between GPIO and I2C. Or am I missing something?

I’m trying to reconcile having the flash, the expansion port and an I2C gyro without changing the pinout…

Edit: I have used the search button and found a post saying that it should be possible. I’ll go ahead and try it, worst case - I’ll drop the gyro.

You can use I2C. But no SPI transfers should take place at the same time.

Because of this you cannot use the arduino wire library as it does I2C transfers in background using interrupts.

I wrote some light I2C code for my Arduboy GT project that reads out a DS3231 real time clock using I2C. You can find the code here.It may be useful for your project too.


I would love to make one of these but I have 100% no idea how to read schematics or what is going on here :rofl:

Edit: I think I may use @Mr.Blinky 's pcb, this is my first time dealing with a pcb so I am really excited :nerd_face:

Hello, I do not know much about flash memory or this kind of stuff, but what is the difference between all of those packages and the one without a packageÉ

The difference is the physical package (the way they look)

SOP8 is a small surface mount package with 8 pins. Where the pins are flat and are soldered to a PCB surface.

DIP package is the normal through hole package where the pins are bent and stick out out the bottom so they can be inserted into a PCB or breadboards.

a Module is a small PCB with the chip soldered on and usually comes with a pin header so they can be inserted into a breadboard or connected using jumper wires.

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Does the GND on the voltage regulator connect to GND on the Arduino? Also what does /WP connect to? I’m planning on using these diodes and these capacitors and this regulator, will they work for the flash cart? If anyone knows I would appreciate the info.


The 3.3V output from the regulator, the same as Vcc and /Hold on the flash chip.

The diodes and capacitors are fine. The dropout voltage of the regulator is probably too high.


So I could use the output from the regulator or /WP?

/WP goes to the output of the regulator. Wire flash chip pins VCC, /Hold and /WP together and connect them all to the output of the regulator.


My Windbond flash chips came today! Still waiting for the capacitors though.

What does the other side of the capacitor connect to? Also I feel like this has been answered before, but what does /WP connect to? My chip has a semicircle on one end, instead of a small circle on one of the corners, so how do I know what side it correct?
Screen Shot 2022-01-20 at 9.56.34 PM

It connects to GND

Oops looks like I forgot something there in the drawing. /WP connects to 5V

That’s called a notch. It helps in determing which pin is pin 1. When you hold the chip horizontal with the notch at the left. the bottom left pin is pin 1 (and the bottom right will be pin 4, the top right pin will be pin 5 and the top left pin will be pin 8).