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I need some advice, I have a bunch of little boards that I am using for home automation and I keep making changes and having to re-flash to boards. I added the ICSP header to all my boards so it is easy to flash them.

Here is the date sheet of lm7805


here is my question I am a huge gadget freak and want to build a push button programmer that i can load a hex file on and go to my different devices and flash them. I just need a nudge in the right direction as far as the code goes, say some example or something. I know that there are pickit3 and 3rd party tools for this but that doesn't help me learn lol.

thanks again

You want to write a bootloader, basically.

Kinda like how Arduino works. On bootup, Arduino talks to the UART to see if there's any new code. If there's new code, then it self-erases itself, copies the new code over, and then starts executing it. The only difference is that your code will be activated by a button. Otherwise, you still need a mechanism to transfer the data over somehow.