Update README.md with more info about firmware flow control speeds and HW vs SW

[Hedda]

Update README.md with more info about flow control speeds as discussed in grobasoz/zigbee-firmware#5

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

[Adminiuga]

What adapters support (wired for) hardware flow control?

[Hedda]

What adapters support (wired for) hardware flow control?

EM358 and EFR32 accoerding to https://www.openhab.org/addons/bindings/zigbee/#ember-ezsp-ncp-coordinator

Please see discussion in grobasoz/zigbee-firmware#5

Again, I did not base that on empirical tests, instead I just stole the recommendation from https://www.openhab.org/addons/bindings/zigbee/#ember-ezsp-ncp-coordinator

[Adminiuga]

yeah, EM358 and EFR32 both support hardware flow control. My question was: What adapter, the USB serial port has wired hardware flow control to those chips?

[Hedda]

My question was: What adapter, the USB serial port has wired hardware flow control to those chips?

So you are saying that not all adapters/dongles/sticks are hardwired to hardware flow control to the EM358/EFR32 SoC?

Hell, I was just trying to be helpful with all the zigpy documentation. I do not even a Silabs based adapter on a daily basis any longer as I have fully switched to using a CC2652R based USB adapter (zzh from Electrorama).