Connection between emontx v3 and Emonpi


I purchased the Emonpi solar bundle in 2020 to monitor my solar production and the total consumption of the house and everything work fine since almost 3 years.
Couple weeks ago, I puchased a “used” emontx v3 with 3 clamps here on this forum to add the monitoring of specific electrical equipment (ev charger, air conditioner…)
Reading the doc, I understood I have nothing special to do to collect data from emontx to the emonpi, just install the clamps and connect the emontx to the power with the ACAC Voltage sensor.
I also tried to use the 5v usb to power the emontx but it’s the same
I did that, but I can’t see datas from emontx in the feeds or inputs of the emoncms interface of the emonpi.
Did I missed someting that I have to configure ? If not, what can I do to troubleshot this situation ?

Hello @solek Do you see anything in the EmonHub log window that might suggest data coming in? It may be something relating to the node decoder not matching… do you see a flashing LED on the emonTx3?

Hello, thanks for your quick answer. No I see nothing related to data from emontx in the log. For the LED I don’t remember, I will look this evening at home and I will update this post

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Yes there is a red LED flashing every 5 seconds between the 9v and 5v input (and I confirm : nothing in the emonhub logs from the emontx, only the mqtt log of the emonpi)

Do you have a UART to USB programmer? any chance to check the serial output of the EmonTx3?


No I don’t have this (this one ? Programmer - USB to serial UART - Shop | OpenEnergyMonitor )

I need it to check the serial output of the EmonTx3 ?

Have you changed the node id on the new Tx3’?

No. How can I do this ?

There’s a dip switch that sets the node id.
See also -
And in fact, that whole page -

Yes, this is correct. (Plus naturally something which allows to see the serial data, like the Arduino IDE.)

Sorry for the late reply, I just had time to check. I tested the dip switch D8 left or right to change the node id, but it’s the same, I see nothing on the emoncms interface of the emonpi.

Is there a solution to “reset the configuration” of the emontx by defaut ?

What can I try exept reading serial data with the UART programmer ? (I don’t have one, and it’s £38.06 included shipping).

Your problem is you’ve no idea which sketch your “used” emonTx V3 has, and even if it is still the factory default sketch, what has been changed by the previous owner. All you know is it appears to be functioning.

Not that you can do without being able to communicate with the emonTx - and this requires a programmer, or somebody with one who you can ask to help.

Go back to the emonPi and look at the emonhub log file - Setup → Emonhub → View Log. Do you see anything you do not recognise? The first line in the log when good data arrives is something like this (but more bytes of data / values for your emonTx), followed by more lines as the data is processed. It’s for an emonTH:

2023-09-22 16:19:26,184 DEBUG    RFM2Pi     9696918 NEW FRAME : OK 23 172 0 0 0 224 2 26 0 4 0 0 0 (-50)
2023-09-22 16:19:26,186 DEBUG    RFM2Pi     9696918 Timestamp : 1695395966.183707
2023-09-22 16:19:26,187 DEBUG    RFM2Pi     9696918 From Node : 23
2023-09-22 16:19:26,188 DEBUG    RFM2Pi     9696918    Values : [17.2, 0, 73.60000000000001, 2.6, 4]
2023-09-22 16:19:26,189 DEBUG    RFM2Pi     9696918      RSSI : -50
2023-09-22 16:19:26,190 DEBUG    RFM2Pi     9696918 Sent to channel(start)' : ToEmonCMS
2023-09-22 16:19:26,190 DEBUG    RFM2Pi     9696918 Sent to channel(end)' : ToEmonCMS
2023-09-22 16:19:26,380 DEBUG    MQTT       Publishing: emon/emonth5/temperature 17.2
2023-09-22 16:19:26,383 DEBUG    MQTT       Publishing: emon/emonth5/external temperature 0
2023-09-22 16:19:26,385 DEBUG    MQTT       Publishing: emon/emonth5/humidity 73.60000000000001
2023-09-22 16:19:26,388 DEBUG    MQTT       Publishing: emon/emonth5/battery 2.6
2023-09-22 16:19:26,390 DEBUG    MQTT       Publishing: emon/emonth5/pulsecount 4
2023-09-22 16:19:26,392 DEBUG    MQTT       Publishing: emon/emonth5/rssi -50
2023-09-22 16:19:26,395 INFO     MQTT       Publishing 'node' formatted msg
2023-09-22 16:19:26,395 DEBUG    MQTT       Publishing: emonhub/rx/23/values 17.2,0,73.60000000000001,2.6,4,-50

'OK 23 ’ tells me the data checksum was good, and it came from Node 23.
You might want to download the log file and look at it with an ordinary text editor.

If there’s anything you don’t recognise, copy the whole line and the next few lines and paste into a post. This will only work of course if your emonTx is transmitting by radio. (It is possible the radio has been turned off if the first user was using Wi-Fi or a serial connection. Your emonTx does NOT have an ESP8266 attached?

Please put 3 ‘backticks’ (normally found at the top left of the keyboard) on a line of their own before the log text, and 3 more backticks also on a line of their own after the log text:


You can add a language identifier after the first 3 backticks: ```php or even ```text if you don’t want any language markup applied.

You need to check the emonhub log first (within emoncms).