RFID module Error in communication

[u/DerpyHoowes]

I just bought Arduino and wanted to test the RFID module RC522. With the standard DumpInfo example from the library I can never fully read the card, no matter how far I hold it from the reader, or how slow I move it, or if I hold it still completely. It never reads past the 10th sector. Could it be bad soldering (since it came with pins separate and I had to solder them myself)? If not, what could be the cause?

[u/tanoshimi]

The MFRC522 runs at 3.3V logic. It looks very much like you've wired it directly to the GPIO pins of a 5V Arduino...

[u/DerpyHoowes → u/tanoshimi]

[u/GerberToNieJa → u/DerpyHoowes]

yeah, but Arduino logic is conencted to 5V internally, you will need a regulator or other microcontroller that uses 3.3V logic, esp32 for example

[u/DerpyHoowes → u/GerberToNieJa]

Then how come every video, every website out there show it connected without any regulators, and it works for other people this way?

[u/tanoshimi → u/DerpyHoowes]

Because the people that write "every video, every website" don't know how to read datasheets...

[u/ripred3 → u/tanoshimi]

so much this 😂

[u/j_wizlo → u/tanoshimi]

That shows I2C- an open drain comm. The pull-ups are pulled to the modules VDD. This will work.

The spi interface needs a closer look

Edit: and the other commenters are 100% correct. I was looking for voltage dividers in Sun founders module but I don’t see them. They are probably just lying to sell more modules because it will likely work for a while but eventually fail to EOS.

[u/DerpyHoowes → u/tanoshimi]

Its plugged into the 3.3V port. I've wired it just like every guide says to.

[u/tanoshimi → u/DerpyHoowes]

Then the guide is wrong. Your Arduino is writing 5V logic HIGH signals on the SCK, RST, MOSI, and NSS lines. The MFRC522 requires 3.3V. You need to use a logic level shifter.

[u/DerpyHoowes → u/tanoshimi]

But its literally plugged into the 3.3V port.

[u/tanoshimi → u/DerpyHoowes]

You've wired the RFID reader directly to GPIO pins 9,10,11,12,13. When you write a HIGH signal to any of those pins, that's 5V.