I have started to build a project inspired by @dombold74https://myhydropi.com. I have Cayenne turning on/off my pool pump, pool light, pool heater and sensing temperature for Air, Pool Water and Pool Heater output water temp. My next phase i would like to monitor the pool pump pressure to determine if there is a problem and send notifications or trigger events based on it.
Are you already using Cayenne for everything you mentioned, or are you trying to just get values from the ADS1115? If you do have everything else hooked up are you using the Cayenne Agent or the MQTT API?
It will just read the value of the pressure gauge. After you add the extension add a generic analog input and select the ADS as the extension and the channel you hooked up to and it will display whatever value that channel reads.