FirmataPlus and the Mega 2560 - MrYsLab/pymata-aio GitHub Wiki

The Mega 2560 has a bug in its boot loader when using the AVR watchdog timer. If you are using the Mega 2560, please use this version of FirmataPlus to avoid the bug or StandardFirmata if you do not require the extended features of FirmataPlus. Please note that older version of FirmataPlus does not support the keepalive feature.