Updating EmonPi to Continuous Monitoring

Continuous monitoring with the Open Energy Monitor EmonPi hardare us now possible (since Feb 2023), see: https://docs.openenergymonitor.org/emonpi/firmware.html. This gives a more accurate measurement of power than sampling at time intervals.

Unfortunately, the process is incompletely documented there and the forum contains several threads which contain errors, distractions, and diversions alongside the information to make the firmware update work. I certainly had to spend time disentangling things to arrive at what is actually a simple procedure, although the forum was a source of some trepidation. Also: do not be tempted into the compilation process described on that firmware web page.

NB: what follows is based on my EmonPi setup. I believe some details will be different for EmonTX + EmonBase setup.

First, ensure that your system is up to date using Setup > Admin > Update: Full Update. This does not change the firmware, but will change what you see available in the Update Firmware Only section. Once updated, you can select options in the drop-down lists in the Update Firmware Only. My hardware is an emonPi and I opted for the “RFM68 LowPowerLabs” radio format (as recommended). Upon hitting the “Update Firmware” button, various messages will appear in the log.

Once it has completed, you will see that there are no updates in Setup > Inputs or Setup > EmonHub. This is because the baud rate and message format have changed. In Setup > EmonHub, use the “Edit config” button to fix this. Changes to two sections are required.

Under “[interfacers]” will be an entry which seems to have gone under different names at different times and/or different hardware configurations. If you have an emonPi, look for the section which contains “com_baud = 38400”, “pubchannels = ToEmonCMS”, and “baseid = 5”. Mine is identified as [[RFM2Pi]]. If you do not have an emonPi then a different baseid will apply. I only changed the com_baud from 38400 to 115200. Leave the rest alone!

Scroll down and find, under “[nodes]”, a section “[[5]]” (matches the baseid above). Leave the “nodename” entry as it is but modify the lines under “[[[rx]]]” to read:

names = Msg, power1,power2,power1pluspower2,vrms,t1,t2,t3,t4,t5,t6,pulse1count,pulse2count,E1,E2
datacodes = L, h, h, h, h, h, h, h, h, h, h, L, L, l, l
scales = 1, 1,1,1, 0.01, 0.01,0.01,0.01,0.01,0.01,0.01, 1, 1, 1,1
units = n,W,W,W, V, C,C,C,C,C,C, p, p, Wh,Wh

Note that the scales line can be used to adjust the power values and Vrms which the emonPi records to accomodate systematic errors due to component tolerances; the text quoted above assumes that this calibration has not been done.

I found that simply saving the config and then using the “View log” button showed this worked. Some people state that EmonHub should be restarted, but I did not find this was needed.

Make a final check that things are working by visiting Setup > Inputs and looking at graphs, visualisation, your app etc. At this point, you might note that there are now two new attributes in the input data: E1 and E2. Unfortunately (again, argh!), the meaning of these (vs the pre-existing power1 and power2) is not properly documented and mentions in the forums are often roundly uninformative.