Hi there,
I am slightly confused with the design of the circuit responsible for controlling the MEGA2560 RESET pin with the ATMEGA16U DTR pin. So I understand that the DTR and RESET lines have a 100nF capacitor between them, which essentially generates a LOW pulse on the RESET line when DTR is pulled low on USB connection. However, I would imagine that when DTR is pulled high after USB disconnection, surely that would generate a pulse on the RESET line equal and opposite in magnitude to the down pulse as the capacitor has to discharge the energy stored in it?
I am working on a custom arduino and am seeing this ~9V pulse on RESET after USB disconnection. However, I do not see the pulse on an off the shelf Arduino. How is this avoided?