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If I was to mass produce a microcontroller board I have designed based around the atmega328 (very similar to an arduino uno) but for one embedded task where I want one program only to be stored on it. I want to make the program read only and impossible to access and impossible to overwrite. The board will not include a USB FTDI chip in order to prevent another program being uploaded via arduino IDE. How would I upload said program to the microcontroller?
Would I have to make use of ICSP pins (I dont know much about that) and if this is an impossible task and so a USB will have to be integrated to upload programs... How would i prevent other programs overwriting the main program and also prevent this program from being viewed? [The main program is written in the arduino IDE]