The weather sensors sketch is located in pypilot/arduino/weathersensors of the pypilot git repository.
To upgrade the sensors, the recommended system is openplotter, or another linux system with arduino support installed.
First it is essential to ensure no other processes are accessing the serial port. For example
sudo service pypilot stop sudo service gpsd stop
Other processes such as signalk-node-server or even opencpn (or others) may be configured to access the serial port, so ensure they are not running.
To install the software needed to compile and load the sketch:
$ sudo apt install arduino $ git clone --depth=1 https://github.com/pypilot/pypilot $ cd pypilot/arduino/weathersensors $ make upload
If there is a failure, repeat the “make upload” command several times. It may be necessary to modify the Makefile and adjust the DEVICE or BAUDRATE. Some boards use a BAUDRATE of 115200, others will use 57600. Some boards may use the atmega32 rather than atmega328. In this case edit Makefile and change the MCU.