SPI over longer distance

Hi,

I have some RFID readers type MFRC-522 and a Arduino Mega2560. The communication between MFRC522 and Arduino is over the SPI protocol. When I use short cables (+/- 10cm) it works fine, but I want to install the readers at +/- 7 meter from the location of the Arduino.

I read something about an convertor to RS422 like the MAX485.

Has somebody experience with this device, and will it work for my project, as describe above.

Thanks

When I use short cables (+/- 10cm) it works fine, but I want to install the readers at +/- 7 meter from the location of the Arduino.

Forget it. SPI is a local bus with a maximum length of about 40cm. You might get it to a meter or so by slowing down the bus significantly but I doubt you get it running over 7m at a reasonable speed.

Spend another Arduino, use it to control the reader and use a communication system in between it and the Mega2560 that is suited for such lengths (Ethernet, RS-485, etc.)

Hi Pylon,

Meanwhile I have done that. I bought 4 Arduino Nano, and 5 Max485 Modules. I connected the RFID reader to the Nano with the SPI protocol, and connected the Max485 to the nano and the Mega. I wrote a polling protocol to communicate between the 5 arduino's.

It works fine now.

Consider using a Nano or something similar at each node and communicate with the RS422 or RS485. It will not add much cost and give you a reliable system. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil