Arduino MEGA + Ethernet Shield 2 + RFID reader cable length

Hi There,

I have a few setups where i need to controll access with rfid.

In most of the setups the arduino and Ethernet board can be connected to the rfid chip with a short jumperwire of 20cm.

In my next upcomming setup i dont have the space to connect the arduino next to the rfid reader, so i need to have 3 meter cat6 cable to connect the rfid chip to the arduino.

When i hook up everything, the Ethernetboard will not connect, and the chipreader will not read.

Is there a smart way to hook up or boost a 3 meter cable to the MFRC522 ChipReader ?

Thanks in advance

You've provided neither links to the hardware you are using nor a connection diagram. Makes it hard for anyone to advise.

I'm assuming you're connecting the Arduino to the MFRC522 using SPI over twisted pair? Twisted pair is likely a poor choice for SPI, depending on how it's hooked up.

Have you tried reducing the SPI clock speed yet?

Hi Arduarn,

Correct assumed :slight_smile: that is my setup.

I use the SPI bus for both ethernet shield 2 and MFRC522 chipreader.

What will i achieve with reducing the SPI clock speed ? I have never heard of this.

Maybe nothing, but it only costs a few minutes to try with SPISettings. The higher frequency your signal, the tighter the requirements on the link. 3 metres of twisted pair could already be too much.

Hi Arduarn,

Would this not increase a chance of error-reading from the chipreader ?

Well you have so many errors now that it doesn't work at all. So if it works somewhat by reducing the transmission frequency then is that not an improvement. No?

Great stuff,

I'll try to play around with the frequency, and report back.