I have tried to search this forum, Arduino forum and Google, but I can not seem to find a really simple example for sending data between Photon and Arduino, defining the Photon as master and using SPI as communication protocol.
I see that the SPI1 library for photon uses the digital pins (which I will prefer), and these are 5-volt compliant so they wont be damaged by the Arduino that has 5V at its pins, and also - the Arduino registers 3.3V on digital input as HIGH, so I should not need a level converter - right?
So, I was wondering if anyone could help me to create a really simple software for both the Photon-master and the Arduino Uno-slave. Let’s say the Photon sends “Hello world” to the Arduino, the Arduino prints this to the console, and the Arduino also returns “Message received” to the Photon so that the Photon can print this out on its console.
Any help would be much much appreciated.