Is there some details about JP5? It is used for control procesor functions or it is only pin terminal?
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Yeah. Mostly he just needs to clarify which board he's asking about jp5 on!
I think pinout signed JP5 (4 holes on board).
I have Arduino MEGA rev 3.
JP5 are 4 pins connected to the 16U2. You could write some code to have the 16U2 do something besides act as just the USB/Serial interface. I believe someone wrote some code to use those pins as a Programmer when connected to SCK-MISO-MOSI-Reset to burn fuses and rebootload the 2560 chip for example.
Unfortunately I didn't bookmark that thread, and good luck finding it.