> > If your timing can afford to be off by a 20ms or so [...] Yes. Too often I see aiming for high end. "What, you can do only 1000000 db insert per second?" In my brewery controller the PID RPi had nothing to do. It controlled the temperature of 7 vessels and 2 chillers. The temperature of a 1000l vessel goes nowhere within a minute and certainly not with the tolerances of the process. The PID didn't emit commands, like open and close to a valve. It just emit a state. T1 to warm, T1 to cold and T1 ok. The logic in the valve microprocessor figured out what to do depending on its current state, open close or do nothing and emitted it's state to the world so the chiller pump could be started or stopped if needed.
Also I wonder a bit about using Mummy or Happyx. One needs a receiver and an emitter but very seldom has the need for request/reply given an Pub/Sub situation. Asynchttpserver as receiver and a an asynchttpserver extended with SSE as an emitter works fine.
