Firmware upgrade/Flash from Linux

Turn off Raspberry, disconnect from power, open the enclosure to reach RESET and FLASH buttons; this procedure can be done both with Z-Bee connected to PC/Raspberry USB port or connected to a Raspberry as hat (remember to adapt serial port in flash string).

If Z-Bee is connected to Raspberry/PC usb port remember to remove wifi module if present!!!.

Turn on and do the following:

Install pyserial to enable Raspberry serial coomunication with flash tool:
```
pip install pyserial
```
Install IntelHex package to permit firmware .hex files use:
```
pip install intelhex
```

Download flash tool:

wget -O cc2538-bsl.zip https://github.com/Gio-dot/Z-Bee-Duo/raw/main/flash_tool/cc2538-bsl.zip && unzip cc2538-bsl.zip    

Download and unpack new firmware to flash, use desired firmware github path, for example
```
cd ~/cc2538-bsl-master
```

wget https://github.com/Koenkk/Z-Stack-firmware/raw/master/coordinator/Z-Stack_3.x.0/bin/CC1352P2_CC2652P_other_coordinator_20210120.zip

unzip CC1352P2_CC2652P_other_coordinator_20210120.zip

Stop Zigbee2mqtt service if it is running.
Press FLASH + RESET: release RESET before then FLASH; adapter is now in flash mode.
Run flash using effective serial port (PORT) and previously downloaded firmware name (FIRMWARE):
```
python3 cc2538-bsl.py -p /dev/ttyAMA0 -evw CC1352P2_CC2652P_other_coordinator_20210120.hex
```
Since version 1.1 to rev.D adapter is provided by auto BSL: no buttons are needed to enter in flash mode. Flash string is the following:
```
python.exe cc2538-bsl.py -p /dev/ttyAMA0 --invoke-bootloader 3 -ewv CC1352P2_CC2652P_other_coordinator_20210120.hex
```

Since rev.E no buttons are needed to enter in flash mode. Flash string is the following:

python.exe cc2538-bsl.py -p /dev/ttyAMA0 -ewv CC1352P2_CC2652P_other_coordinator_20210120.hex

Reboot