I am building a modular microcontroller system using a mega644p as the main processor, which interfaces to a high speed counter board with a 328 on it, and to a few other relay and opto optoisolated boards with dumb IO expanders etc. All going well. The communications backbone between boards is I2C.
What I am wanting to do now is to modify the main processor board to have ethernet on it. The 644P has 2 serial ports. Currently I use 1 for programming and sending data to a Python program on a PC, and the other for talking to a 24x8 Character LCD with a serial backpack.
Is there an ethernet module available that may be part of someones shield, that I can purchase somewhere and plug into my processor board? I can effectively make my processor board have the required header to plug it it. I remember seeing one somewhere but havent found it again yet.
The other question is, do these ethernet shields on the arduino's utilise a serial port for comms, or do they use SPI or something? Basically I want to keep the 2 serial ports I have the same, so if there is an ethernet module available which talks on SPI or something then that would be perfect.
Basically I want to change the comms to the Python program on a PC from the serial port, to the ethernet port, as I want to add in a hand controller to the project, and that would talk over the serial port instead.
If anyone has seen an ethernet module that is arduino compatible (not a full shield, but a module that plugs into a shield), can you reply to this please. If it talks over SPI then that is exactly what I need.