Physical Solenoid Control #89

We should have the control settings on the configured solenoids be able to interact with the physical solenoid via downlinks. The firmware has an open PR for the firmware code to allow for downlinks. ENTs backend API endpoint is being developed to send payloads to TTN as downlinks. Once this is finished NodeFlow can create the payload, forward it to ENTs backend, and have ENTs forward it to TTN to schedule the downlink.

Currently there is an open PR on the ENTs backend for the downlink forwarding to ttn

Downlink PR: jlab-sensing/ENTS-node-firmware#351