Kamstrup HAN P1 module seems not to work?

[j74nilsson]

Just got the P1 module (Kamstrup model 6840005.1) and confirmed that the port is activated. However the module is not feeding 5V (manually read fluctuating 50-150mV between pin 1 and 6) and obviously I do not get contact with my esp32.

I then removed the soldered 5V line and connected to USB and P1 port simultaneously. The device powers up and communicates with home assistant, but no data is read from my Kamstrup Omnipower meter. Any ideas/suggestions?

[Beaky2000]

If it is not outputting 5V, I guess the port is not working properly and it is not really surprising that it is not sending any data...

With an oscilloscope you could determine if there is some partial functionality or if it is completely dead. I suppose that with a few LEDs, some resistors and a multimeter, you could check if there is any output comming from the port...

[gunstr]

Just sharing a bit of experience...

I bought a P1 module for a Kamstrup meter three years ago. No guarantees that all modules are the same but for the one I got there were contradicting statemets in the documentation if pin1 (5V) is an input or output. I asked Kamstrup support via the electricity company for a clarification and got a very clear message in return that it's an outpout and that it's absolutely forbidden to feed anything into that pin.

After many weeks of troubleshooting why the module did not send out any data - including replacement of the module and even the complete meter (kudos to Varbergs Energi) - I decided to break up the housing of the module and do some reverse engineering. The customer facing section of the board was as expected fully isolated but to my surprice there were no isolated power supply feeding that section from the meter itself. The only way to power up the drivers and get any data out from the module was to feed 5V in to the P1 connector, pin 1.

Again - no guarantees that this is the case for all versions but when feeding 5V into my module it all works and have done so for three years now with no issues.

[j74nilsson]

This is interesting. I actually had a thought like this myself but did not dare to feed 5V to the module.

Would feeding the esp32 with an USB and solder back the pin 1 from RJ12 onto the 5V pin on the esp32 work as for feeding 5V into the P1? (I guess feeding an esp32 with USB powers up both the 5V unregulated and 3.3V regulated pins on the board? True or not true?).

[Beaky2000]

Yes, that should work. When powered by USB, the ESP modules typically output 5V on the 5V pin, which is why I don't (normally) recommend connecting USB and the P1 port at the same time. But if the 5V on the P1 port is an input, this should work fine!

[j74nilsson]

I can confirm that this was the case. I finally got the time to resolder my device and added 5V input via USB. It works excellently! Need to tidy it up though…

[Beaky2000]

Kamstrup P1 modules seem to be a mess... I think I recall reading about how the connector where the module plugs in actually has all the connections needed (5V, signal etc) but it is not a standard connector, so you need to hack something together. Also there is no guarantee that this is the case for all Kamstrup meters, or that I remember correctly.