Sometimes it's more convenient to connect the emonTx V3 directly to a Raspberry Pi base station rather than use RF.
Both the Raspberry Pi and emonTx V3 run at 3.3V so the serial Rx and Tx serial lines can be directly connected. The raspberrypi's 5V supply can be used to power the emontx which is then stepped down to to 3.3V through the emonTx V3's voltage regulator. 5V is provided by the red wire. The ground connection is the black wire and the data going from the emontx to the raspberrypi is the green wire. I haven't connected a wire for serial data going the other way but this is a possible option if two-way serial is required.
|emonTx V3 > Raspberry Pi Connection|
Here's a simple direct serial output sketch for the emontx v3 on GitHub here
On the raspberrypi if you just want to forward the emontx data to a remote emoncms this can be done with the oem_gateway developed by Jerome which is on the standard rock solid forwarder image
See our blog post about how to configure the oem_gateway for work over a serial link rather than RFM12B
For the future we are working on developing an energy monitoring shield for the Pi to create an all-in-on Pi-energy-monitoring unit, see dev forum thread: http://openenergymonitor.org/emon/node/3937To engage in discussion regarding this post, please post on our Community Forum.