ping1d: support auto firmware baudrate detection

[ES-Alexander]

Relevant to #29

[patrickelectric]

We did some tests in the pass and this turn out to be not reliable, did you check with a normal arduino , did it work every single time or when both Arduino and Ping got powered on simultaneously ?

[ES-Alexander]

did you check with a normal arduino , did it work every single time or when both Arduino and Ping got powered on simultaneously ?

For peace of mind, I just tried it >5 times in an Arduino Uno (unplugging the Arduino each time, so both devices get power at the same time), then a few times with the comms wires unplugged initially and then plugged in once the serial monitor was getting data. I then tried the same tests on a Mega 2560 clone, with both software and hardware serial, including testing 115200 for hardware serial as well. No issues on any of the tests - seems to be super robust on my end.

Edit: Just did some extra tests - it also works consistently at both 9600 and 115200 baud on the Feather M4 Express (SAMD). Only hardware serial, because software serial isn't supported for SAMD architectures.

[patrickelectric]

LGTM