Hello. I'm a student of electrical enginering and i'm trying to build my own simple microcontroller. I should have 22 GPIO pins and should be powerd and communicate over POE with Raspberry Pi who runs a MODBUS TCP/IP server. I'm fairly new to electronics
so i don't really know how to approach the problem. I don't want to complicate things and start from beginning and would like to know what what kind of simillar solutions were already done? The biggest problem seems to be POE. I found perfarduino whitch seems to be a simple solution but i really have no clue how to set up POE. And thoughts?
Would be really grateful for any kind of help.
This Nick Gammon blog shows minimal circuits for 2 different stand-alone AVR controllers.
The first is a 28 pin 328P. With external oscillator it has 20 I/O pins but running on the internal 8MHz oscillator frees up 2 more pins. ]
The second is a 40 pin 1284P with 8 times the flash and RAM. It's got 2 UARTs, one can be used to print status or debug over the USB cable and still have the other free.
The blog explains everything including programming the chip.