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Hi
I have the following setup:

Opentherm Wifi interface v2.0 from nodoshop
NodeMCU Firmware Version0.9.0+21bea01 (06-11-2021)
OTGW PIC Firmware Version5.1

I have a DS18b20 with a 4k7 resistor pulling the data line to 5v
The DS18b20 is on a 4m cable, with the pull-up at the PIC end

The nodoShop silkscreen does not show the GPIO, however the documentation states that it is the three pads below the PIC, closest to the CE mark
see photo here - https://ibb.co/tx2xHFf

In opentherm monitor I have set GPIO port A to 5v
GPIO port B to Temperature

I have checked that I am seeing 5v between the black and red wires, as expected

However opentherm monitor shows no external temperature. Anything obviously wrong?

I've replaced the sensor and pull up hardware entirely, with no change in symptoms.

Not sure how best to debug this....is there any way to confirm if the PIC is trying to read from the sensor?

The connections look correct. But is your thermostat actually requesting the outside temperature? If not, then the information is never reported by the OTGW and so OTmonitor can not display it.

If the sensor is working correctly, the output of the PS=1 command will include the measured outside temperature.

Ah! That could be the issue then!
I didn't realise that if the boiler was not requesting outside temperature it would not be reported to the otmonitor

Interestingly, running PS=1 reports a believable outside temperature tonight of about 7 degrees C....but my 1 wire sensor is actually inside currently, so is actually about 18

My boiler is a Vailant EcoTec Pro 24 with a VR33 openTherm board
The manual discusses external temperature compensation,

PS: 1
00000011/00000000,
90.00,
00000001/00000001,
0.00,
0.00,
0.00,
0/0,
18.00,
0.00,
1.50,
0.00,
0.00,
14.80,
66.00,
0.00,
7.89,
66.00,
0.00,
0,
65/35,
0/0,0.00,0.00,00000000/00000000,0,0,0,0,0,0,0,0,0,0

As I wrote, the thermostat has to request the outside temperature. The boiler is a slave in an opentherm setup. It doesn't have the ability to request anything.

That you get a wrong temperature is odd. Does the value ever change? Are all results incorrect?

Ah Ok, sorry I misread. In this instance the thermostat is a Drayton Wiser. I will ask them if they support this call in their heat hub.

The data looks much more sensible now in either case:

00000011/00001100,
90.00,
00000001/00000001,
0.00,
0.00,
0.00,
0/0,
18.00,
87.00,
1.40,
0.00,
0.00,
15.00,
79.00,
0.00,
15.19,
59.00,
0.00,0,0/0,0/0,0.00,0.00,00000000/00000000,0,0,0,0,0,0,0,0,0,0