MemberMay 6, 2019 at 1:21 pm
yes, power pins on pinheader are limited to 200 mA in total, not every pin.
3V3 peripheral will not work because ATMEGA2560 is powered from 5V and will not work with 3V3 level device even when device is tolerant. In case of input, level for processor will be too low. When you will use device which is 5V tolerant, you can use it only, when the external device has no output to the processor.
The best way will be to use levelshifter.