I had project working fine on my Arduino Uno Due to lack of SRAM I swapped in Mega 2560 with all connections same Result was a) my micro SD drive failed at init b) my GSM unit failed init ( fona.begin )
SD: Only idea I had was to reformat, even though card was working fine in my laptop
GSM: Tried change to HW serial (was using Software on Uno ) No change Not sure what serial FonaTest would use, I tried all 3 HW serials I have on 2560
General: Not sure if I have power enough .. ? With both external power and USB connected I had 4.70 V on my project board (feed from 2560 +5 V ) Only external power give me 4.47 V Little suprising for me was I had less power to project board when I feed from Vin ... My external power is for 2 A
Any other known problems for GSM and SD drive when going from Uno to Mega 2560 ?
All testing was done with the Example programs. Those working on the Uno (as well as my own programs)
Any idea on this would make me happy ;)