I’m intending to use several Arduino Boards as a cheap means of controlling a number of RFID Readers which will be used to detect the position of Locomotive Engines on my LEGO Train Layout. That said I need a way of connecting these Arduinos to the Raspberry Pi which is the Master Controller for the layout.
The easiest way of Connecting an Arduino to a Raspberry PI is using USB, however the PI’s USB ports are need for WiFi Keyboard, Mouse, etc. So in many cases USB is out, especially if you are using a Raspberry Pi Model ‘A’.
Then there is RS232 which both support, however the PI runs on 3v3 whilst most of the Arduinos (UNO & Mega) use 5v, so one needs to add a ‘Level Converter’ between the two devices. It also limits you to just one Arduino and if you need to use more than one, another solution is needed.
Both the PI and Arduino support two additional types of communication for talking to peripheral devices. First there is SPI which is a high speed serial protocol, and I2C. Like RS232, SPI needs level shifters, but this is not exactly the case for I2C.
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