I found a used hot tub online, that's a couple of years old and I decided I can make a cool project out of it. The built-in controls were already annoying and time-consuming, so that gave me further reason to tinker with it. In order to save energy, I lower the pool temperature when not used, but if I wanted to use the hot tub, I had to turn the temperature up 4 hours in advance. As an example of what I mean by saying annoying: In order to save energy, I had to lower the pool temperature when not used, but if I wanted to use the hot tub, I had to turn the temperature up 4 hours in advance. Another thing that happened was that somehow the circulation pump decided to turn on randomly during the night - that would probably have gotten under control if I had read the manual, but as a tinker I prefer to tear out the controls and use an UniPi 1.1 instead.

With the UniPi and running nymea on it, I was able to turn on/off each pump, set the hot tub mode "Ready" or "Summer", check the temperature and switch the blower. With the remote connection I can now preheat the hot tub before I come home and get a push notification when the hot tub reaches it's target temperature.

See the full project description here:
https://www.hackster.io/124582/open-source-hot-tub-controller-e0a1f3

Thanks, worked out for me

To be more specific I use Raspbian GNU/Linux 9.1 (stretch) with a Neuron L40x and a xS30 Extension.

/etc/evok.conf:

;[EXTENSION_1]
device_name = xS30	
modbus_uart_port = /dev/extcomm/0/0		
allow_register_access = False		
scan_frequency = 2			
scan_enabled = True			

DIP switches on the extension are all OFF, cable length 30cm

I've a hard time to add an extension to evok, I tried different settings in the /etc/evok.conf - no success. Found also no documentation about the extensions and how to add them without using mervis.