update Turns out it is 'problem' with bootloader, i have had a fix created and submitted to arduino project https://github.com/arduino/Arduino/issues/2101 if anyone is interested in compiled bootloader with this fix, let me know
edit changed title, and added this comment to reflect changes * since OP found out it happens on all my mega based boards but not my 328 ones. * believe this is due to 328 bootloader having MAX_ERROR_COUNT parameter but 2560 not * opened ticket https://github.com/arduino/Arduino/issues/1974 * what do you think ? can it be added ?
im finding if i have a transmitting device hooked up to serial 0 it is preventing the arduino from booting... im guessing this is because it is expecting to get a new sketch ? (but is instead just getting the signal from a generic serial device)
does this sound feasible, and any suggestions to get around it ?
as if i plug in the device after boot, it is fine, but i need it always connected, also the device starts transmitting straight away. (once it gets power)