Problem: sync with firmware

With an USB-RS232 adapter, in mt-r027/upload-firmware.bat

* wintools\megaloader.exe firmware\vems.hex -wtE

says "no hello from AVR" and refuses to upgrade the firmware. There is strong suspicion that some USB-RS232 adapters tend to lose a character when baudrate is changed (eg. the default case when going from firmware 9600 baud to bootloader 19200 baud). With prog.pl, some trick was needed to make it more robust to handle the case.

workaround for users who face this: try to use 9600 baud like:

* wintools\megaloader.exe firmware\vems.hex 9600 -wtE

or

* loopback the serial TX-RX (short ECM RS232 connector DSUB9pin2 and DSUB9pin3 with a small wire)

* power the ECM

* remove the loopback short

* connect the notebook

* use megaloader without "t" option:

** wintools\megaloader.exe firmware\vems.hex -wtE

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