![]() ![]() While the thought of using a op-amp to 'unload' the pin 13 led current burden from pin 13 was a good idea in principal, it appears that it can leave one with random pin 13 behaviour when pin 13 is not being used by the user's sketch. If this is the case it just further proves the law of "unintended consequences". I suspect even adding a 1 megohm pull-down external resistor to pin 13 would keep the led off in that case. So I think it's the newer hardware design using an op-amp section to drive the led that is responsible for any randomly on or off led when the users sketch starts, if that is indeed the true symptom being seen, as the result of the op-amp 'seeing' a floating input pin condition. So I think that leaves optiboot innocent of any randomīehaviour of pin13 led being on or off when starting a sketch symptom, if should always be off. Here you will find all of the technical documentation and support files for the Arduino Mega 2560 Revision 3. ![]() Input mode and the internal pull-up turned off. So my conclusion is that optiboot leaves the bootloader and jumps to the application code with pin 13 in put your main code here, to run repeatedly: put your setup code here, to run once:ĭigitalWrite(13, HIGH) //enable pin 13 pull_up When it was run one can see the led on but very very dim. If in input mode, other wise if the pin is left in output mode the output will be 'full on'. ![]() Removed power and then repowered on with battery, led 13 still off.Īdded the below to bare minimum example which should just enable the internal pull-up for pin 13 if the pin Loaded and ran the bare minimum example sketch and when run pin 13 led is off. The bootloader flashes the LED and it is probably chance that it is HIGH (although maybe INPUT) when it finishes.Īs I said I don't own a Rev3 Uno, but I am running optiboot in an older duem. ![]()
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