Industruino and RC522


Recently I've bought an Industruino D21G and the Ethenet module, all works perfectlly, however when I connect a RC522 reader to the board, the Industruino doesn´t recognize it, the reader is working on an Arduino Leonardo. I'm using this library to control the device:, I've tried the example ReadNUID changing the Serial to SerialUSB, but the Industruino doesn´t recognize the reader, Im wiring the RC522 just like this:


RC522 3.3V --> Industruino protoboard 3.3V pin

RC522 RST --> Industruino protoboard D4

RC522 GND --> Industruino protoboard GND pin

RC522 SDA --> Industruino protoboard D5

RC522 SCK --> Industruino protoboard SCLK pin (next to the expansion port)

RC522 MISO --> Industruino protoboard MISO pin (next to the expansion port)

RC522 MOSI --> Industruino protoboard MOSI pin (next to the expansion port)

Can anyone help me?

Many thanks in advance


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Asked on 8/19/21, 12:37 PM

Hi, there could be multiple issues, please try these

(1) the D4 pin is the chip select of the SD card in the Ethernet module, so you cannot use this pin when the Ethernet module is connected. use D7 instead. see

(2) the library file contains Serial.print change all to SerialUSB.print

(3) are you using the latest version of the library, it seems earlier versions had trouble with faster MCUs (the D21G runs at 48MHz) the SPI speed should be fixed at 4MHz as in

(4) there may be a conflict on the SPI bus, which is also used by the Ethernet chip, the SD card, FRAM chip. can you try a simple library example without the Ethernet module connected

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Answered on 8/20/21, 2:41 AM

I've tried your suggestions, but unfortunatelly I've got the same result, the industruino doesn't recognize the RC522, I'll continue doing research to find a solution

on 8/20/21, 10:45 AM

Hi, i have tested with the latest version of the library 1.4.9 and the example 'ReadNUID' and it works for me, even without editing the library files for SerialUSB. I used RST_PIN = 5 and SS_PIN = 7 and replaced Serial with SerialUSB in the example. I used the pins on the expansion port, and 3V3 from a the screw terminal. Send me an email on if you want a picture of the wiring.

on 8/24/21, 8:16 AM

Hi Tom,


Many thanks for your reply, I'm going to take a look at the things you've told me, I'll post the results.

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Answered on 8/20/21, 8:17 AM

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Asked: 8/19/21, 12:37 PM
Seen: 964 times
Last updated: 8/20/21, 8:17 AM