115200 hardware flow control verses 57600 software flow control Silicon Labs EmberZNet NCP EZSP firmware

[Hedda]

@walthowd FYI, submitted PR to update bellows README for zigpy with more info about flow control speeds in zigpy/bellows#391

Note that there are generally two image versions of the Silabs EmberZNet NCP firmware in use. One version operates at a baud rate of 115200 with RTS/CTS flow control (i.e. hardware flow control), the other operates at a lower baud rate of 57600 with XON/XOFF flow control (i.e. software flow control). If you are flashing firmware image to your own EM35x or EFR32 adapter then it is advisable to use a version with hardware flow control, Many available commercial dongles (e.g. Nortek HUSBZB-1) seem to ship pre-flashed with a firmware that uses the lower speed and software flow control.

Paraphrased from https://www.openhab.org/addons/bindings/zigbee/#ember-ezsp-ncp-coordinator