I am trying to figure out the best practice for ICSP in a 3v3 board (no 5V devices at all)
In my current design I am using a Arduino pro mini (3v3, 8mhz) with one SPI device and a couple of I2C sensors. Everything is running at 3.3v. Design is working fine (still need to fix some little things in the code) and I am planning to design a custom PCB with all my components laid down.
My biggest concern is the ICSP of the atmega328(P) I am going to use as main microcontroller: is it possible to burn the arduino bootloader using only 3v3 signals? The SPI device I have to use, apart the atmega, is NOT 5V compliant. So I want to avoid burning it by feeding 5v via SPI lines.
My idea is to use another arduino as programmer: I have a seeeduino which can work at 3.3V (so all the signals from it will be 3.3v), and powering my custom board via its own supply (which of course will be 3.3v). I saw it is possible to program the arduino with 3.3v signals (example: via raspberry pi) so in theory my plan should work. Any contraindication? Or am I missing something?
Is there any other precaution I should consider? Should the other devices (everything except the atmega) be unpowered during ICSP or they can be powered? Of course my concern is the SPI device, the I2C should be just fine.... should
Of course any comment or suggestion is well appreciated, thanks since now to who will help