Thank you! That actually does clear it up. I already have a Home Assistant instance which is different than the Pi that is going to use the Hat. Since it is separate, I am making it more difficult on myself. However, like you said, the Hat will be a serial gateway and I will have code on the Pi that reads and parses the serial API data. Then it is up to me get that to Home Assistant. Since my initial use case is to monitor a number of BME280s, I can publish the data to MQTT. Then HA or Node Red can use it. I appreciate your response.