P1 troubles

[BartSr]

For years domoticz is stable running.
Recently two ratio solar chargers for EV's have been installed. Homewizzard P1 splitter (external supplied too) provides data for EV chargers and Domoticz. P1 now fails
Both for domoticz and EV's.
Chatgpt says this is because of how domoticz uses P1.
Any idea to solve this problem?

[waltervl]

Domoticz is only reading the telegram message so nothing Domoticz can interfere.
The P1 splitter is the probable root cause.
Does each charger has its own cable, so you have 3 P1 cables coming out? What happens if you disconnect one of the charger P1 cables?

[willemd]

The previous years you were using Homewizard P1 but without the splitter?
And now you added the spliiter?
Did you follow the instructions and connect the power supply to the P1? It should be connected to the usb of the P1, not to the usb of the splitter.

You can check whether the P1 is working by typing the URL of the API in a browser.

[BartSr]

@ Walter
The ratio solar chargers are connected to internet mainly to be controlled by an app. One charger is set as master the other one as slave. There is an interconnection between the chargers to balance availbale power over both chargers. The P1-data goes to a so called sensorbox. Sensorbox is managing the required power for the chargers in respect to max. available gridpower just to prevent from blackout caused by main circuit breakers overload. Communication between sensorbox and chargers goes via bluetooth. Once the P1 sensorbox signal is taken away both chargers return a communication error and charging is stopped.

@ Willemd
I am not talking about the Homewizard P1 minitor but it regards the Homewizard P1 'multiplexer' to have three devices using the 'slimme meters' P1 comm port.

As mentioned before, domoticz was running using solely the P1 connection of the gridcounter.
The EV chargers also needs the P1 signal for proper working and that's the reason the Homewizard P1 multiplexer cam in.

This is the conclusion of chargpt (for what's is worth...)

Conclusions: HomeWizard P1 multiplexer + Domoticz + Ratio Solar
1. HomeWizard P1 splitter is not a true multiplexer
Despite the name, the HomeWizard P1 splitter does not actively buffer or independently replicate the DSMR data stream.
What it does instead:
Passes through the single serial P1 data stream
Relies on well-behaved listeners
Has no arbitration, no buffering, no timing isolation
This is fine only if all connected devices behave passively and politely.

2. Ratio Solar EV charger works reliably on the P1 splitter
Your observation confirms this:
Ratio charger (via wireless sensor box)
Reads P1 data read-only
Does not request data, does not reset the port
Has predictable, low-impact timing

Result: stable operation, correct solar charging behavior

This is exactly the kind of device the HomeWizard splitter can handle well.

3. Domoticz P1 integration is the destabilizing factor
As soon as Domoticz P1 is connected:
Short time later → P1 communication failure
Ratio / HomeWizard chain becomes unstable
Sometimes works for hours or days, then fails
This strongly indicates that Domoticz:
Actively opens/closes the serial connection
Possibly toggles DTR / RTS
Parses DSMR aggressively
May not fully respect DSMR timing or voltage constraints

The splitter cannot isolate Domoticz’s behavior from the other device.

4. Why it sometimes works “for a week”
This is important — and misleading if you don’t know why.
Likely explanation:
Timing coincidentally lines up
No reconnects/restarts
No CRC or framing errors during that period
But:
The setup is marginal
One reconnect, Domoticz restart, or timing hiccup is enough
Failure is inevitable, not accidental

A week of uptime does not mean the setup is sound.

5. Root cause (summary)
The real issue is:
Two active P1 consumers on one passive splitter
Specifically:
Ratio = passive listener → OK
Domoticz = active serial client → NOT OK
HomeWizard splitter = no isolation → conflict
Final verdict
HomeWizard P1 splitter + Domoticz + Ratio Solar

Structurally unreliable

HomeWizard P1 splitter + Ratio Solar only
Stable and supported
HomeWizard P1 splitter + Domoticz only
Usually works, but still depends on meter and cable quality

Recommended solutions (ranked)
Best solution
One real P1 master → distribute data in software
Use Home Assistant / ESP / P1 reader as single P1 master
Forward data via:
MQTT
HTTP
Modbus TCP
Let Domoticz & Ratio consume derived data

Hardware-safe option
Active P1 buffer / isolator
ESP32 with optocoupler
Commercial buffered P1 splitters (rare, but real)
Not recommended
More passive splitters
USB-TTL Y-cables
Hoping Domoticz “behaves nicer”

[willemd]

How is your setup powered? Maybe signal gets low because of nr ofdevices.

[FireWizard]

Hello @BartSr,

Did you check the connections to/from the P1 splitter?

The output of your P1 port on the smart kWh meter should be connected to the input (most left RJ-12 port) of the P1 splitter!
The other 3 ports are outputs for Domoticz and your EV's sensorboxes.

I have a similar setup. I recommend also to power the splitter with the external (supplied) power supply.

Regards

[BartSr]

@willemd
Splitter is supplied from dsmr meter with,as advised ,a well qualified external power supply.
@FireWizard
Yes, allthough not very clear indicated the leftmost connection is for connection with dsmr meter. Both splitter as well as EV sensor box are equipped with external power supply too.

[RonkA]

Don't know if it really matters but are the power-supply's for the p1 all on the same phase?

[willemd]

If everything else fails and you can't find a solution, you could try to replace the current wired Domoticz P1 with a Homewizard P1 that can be read by Domoticz via Wifi.

[BartSr]

@Willemd
This sounds like a solution.
But prior to that solution I will try a ser2net 'interface'.

[FireWizard]

Hello @BartSr

@willemd said:

If everything else fails and you can't find a solution, you could try to replace the current wired Domoticz P1 with a Homewizard P1 that can be read by Domoticz via Wifi.

But how do you intend to connect your EV sensorboxes?

You said previously

For years domoticz is stable running.

That means, that before you installed the HomeWizard P1 splitter between the P1 port of your kWh meter and Domoticz, your connection was okay. Right?

Probably you inserted the RJ-12 connector, that has been installed in your P1 port previously, in your P1 splitter device.
It is inserted in the most left port on the device, as you said.

Do you see a flashing white LED above the most left port? In case of a DSMR5 is flashes every second. DSMR4 or lower, it will flash every 10 seconds.

If not, your connection between the P1 port on the kWh meter and the splitter is faulty. Cable? Connectors?

If it is flashing, do you see white flashing LED's on the connected other ports of the splitter?
They should flash just after the most left port flashes.

Your green "Power" LED is steady?

If they flash, disconnect your EV sensor boxes from the splitter.

Then Domoticz should work properly. You can also check with a terminal program, that you receive correct P1 telegrams.

Try and check this first.

Regards

[willemd]

Hello @BartSr

@willemd said:

If everything else fails and you can't find a solution, you could try to replace the current wired Domoticz P1 with a Homewizard P1 that can be read by Domoticz via Wifi.

But how do you intend to connect your EV sensorboxes?

I assume he will still need to use the P1-splitter to provide data to the three devices. I only suggested this if he cannot analyse or solve the problem further. I agree I would also check the splitter first, then one by one connect the devices, in different sequences, to try to pinpoint the issue. Try to readout each device and see what it shows.

[FireWizard]

Hi, @willemd,

I believe, that it is a hardware issue. I own a similar setup, where I use a port for Domoticz and another for load balancing of my EV charger.

So, as you said, at the end @BartSr still needs a splitter.
Another option is to read the the P1 telegram and to push it to MQTT.

But still there exist the possibility that the EV sensor-boxes ( which I do not know) produce something that disturb the functioning of Domoticz or the splitter.

My first test would be (except of the already suggested checks of the LED's) to make it work with Domoticz only, as that is known to work.
So only 1 port connected to the splitter and then one by one add the others.

@waltervl said already

The P1 splitter is the probable root cause.

Regards

[willemd]

Based on the info given I cannot conclude that P1 splitter is the root cause. This is because he changed three elements in one go, i.e. he added the splitter and the 2 EV sensor boxes at the same time. Therefore he needs to take a step by step approach to pin it down.

[FireWizard]

Hello @willemd,

Agreed

[BartSr]

@Willemd
Maybe I was not clear enough.
Running Domoticz, connected to smart P1 meter worked fine for years.
EV chargers (2off) have been installed. They are using just one sensorbox (make ratio) . Sensorbox communicates to both chargers by bluetooth.
To multiply the P1 signal the homewizzard splitter is used incl. external power supply.
On Homewizard green LED is steady. whereas White LEDs blink in 1 sec. frequeny.
Homewizard has already been replaced for another (new) one.
Supplier of EV-equipment incl. Homewizard has been informed and I'm awaiting their response.
Meanwhile (as I like to continue logging P1 value using domoticz) I willl try to use an raspberry pi with ser2net installed. Same config I am using at house as distance between smart P1 meter and domoticz is to long.
As soon as more news is there I will revert with the update. Next Tuesday I'm at location so can give it a try.

[willemd]

So the Ev charges are not connected to the splitter? You have only the sensorbox and Domoticz P1 plugged into the splitter?

[BartSr]

@willemd
That's correct.

[zicht]

Maybe also check if your energy provider still is getting readings ? Should be on your energy overview to see the counters on last month switch

[FireWizard]

Reconnect the P1 smart meter again directly to Domoticz, so that the old situation is restored, as it was before the addition of the splitter. Does it work again? If not, disconnect Domoticz and check with a terminal program.

Regards