Add the following to emonhub.conf in the [interfacers] section:
### This interfacer manages the EmonTx3 ESP format serial
Type = EmonHubTx3eInterfacer
# Un-comment line below if using RS485 adapter
#com_port = /dev/ttyRS485-0
# default com port if using USB to UART adapter
com_baud = 115200
pubchannels = ToEmonCMS,
The idea is to tie the components together via a single connection from each component, then
earthing that connection. The “connection” is usually a chassis or “frame,” but lacking that, the negative power terminal on each component can be used. Doing that keeps all of the voltages referenced to a common point.
It’s a lesson I learned when I did GPS testing for the USAF.
“Component” means the Pi, the emonTx, and anything else that is powered.