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Hello,

First of all, OpenTherm gateway is awesome!. I have an intergas Kompact boiler with an iSense thermostat.

The problem I have is that the DS18b20 sensor does not work when I use a longer cable (cat 5 utp) 5+- meters. I've tried to use a 4k7 and 2k2 resistor. Both work on an arduino but not on the OTGW. Is there a magical trick to this?

My other issue is that recently I had to change the vRef down to 1.042 after a lot of "Error 03". Today I had to change it back to 1.250 after the "Error 03" appeared again. Is there a known cause for this behaviour?

Regards,
William

I have wondered about that from the beginning, as you can see in the post where I first announced this feature. In over two years you're the first person to mention any issues.

The problem is that the gateway is just using a GPIO pin for the 1-wire bus, not a proper 1-wire interface. So the possible cable length was always going to be a lot less than the theoretical maximum for a 1-wire bus.

You may be able to achieve some improvements by terminating the cable to reduce reflections or use different wires of the CAT-5 cable. But that will give you another meter or 2 tops.

If you need much more than that, you will probably have to switch to a slew-rate controlled interface, built with some external components. That would also require changes to the firmware because then you'll need a separate input and output pin.


There should normally be several Vref settings that work. It's best to pick one in the middle of the working range. If you use one close to edge, the recent warm weather could have enough of an influence to shift things over the edge. But normally you shouldn't have to re-adjust Vref once you've found a setting that works. Maybe you have a flaky component or bad contact somewhere.

Have you been able to determine if the error was detected on the thermostat- or the boiler side? I.e.: Do you see the errors instead of T messages, or in response to T messages?

Thanks for the reply!

Ok I think the easiest way to fix the issue with DS18B20 is to relocate the OTGW. I'll update later on this.

The recent warm weather that was my theory however I thought it was stupid! but yeah, when it got hot the OTGW started with Error03 so I adjusted it down. Then last sunday it cooled down a lot and I had to turn it back to 1.250. I use a stripped CAT 5 pair for communication to the boiler and some 2 wire installation cable for the connection to the Thermostat. I think it lost communication with the boiler, I'll check the logs. The only strange thing was that at a certan point, the heater started heating? haven't been able to reproduce the issue just yet and momentarily I'm connecting a ser2net gateway so that I can monitor the OTGW continously.

Also I was wondering, is there a cli version of the otmonitor? My server is headless.

Regards,
William

w1ll14m wrote:Also I was wondering, is there a cli version of the otmonitor? My server is headless.

Well, there's: otmonitor --daemon