[OpenTRV-interest] Potential bug with Remote Call For Heat

[Damon Hart-Davis]

Hi,

In JIRA as TODO-520:

First fix attempt:

      // Potentially accept as call for heat only if command is 0x26 (38)
      // and the valve is open enough for some water flow to be likely
      // and the housecode is accepted.
      if(0x26 == command.command)
        {
        // Initial fix for TODO-520: Bad comparison screening incoming calls for heat at boiler hub.
        const uint8_t mvro = NominalRadValve.getMinValvePcReallyOpen();
        if((command.extension > (mvro << 1)) && // Quick approximation as filter with some false positives.
           (command.extension >= ((255 * (int)mvro) / 100)) && // More accurate test.
           (FHT8VHubAcceptedHouseCode(command.hc1, command.hc2))) // Accept if house code not filtered out.
          {
…


> On 10 May 2015, at 07:49, gary.gladman at talktalk.net wrote:
> 
> Hi
> 
> I have been monitoring RCfH and noticed that the boiler would continue though the valve was below the Minimum Valve PC Really Open (10% - default).
> 
> I noticed the following code and think it might be the cause ...
> 
> OpenTRV\Arduino\V0p2_Main\FHT8V_Wireless_Rad_Valve.cpp:
>       
>       // Potentially accept as call for heat only if command is 0x26 (38) and value open enough as used by OpenTRV to TX.
>       if((0x26 == command.command) && (command.extension >= NominalRadValve.getMinValvePcReallyOpen()))
> 
> My understanding is that in the FHT8V protocol the command extension is in the range 0..255 whereas Minimum Valve PC Really Open is loosely 0..100 therefore 10(%) is compared against extension 10  which as a percentage means (10*100/255)  3% hence the boiler is being shut off significantly later than expected and with valves more closed than intended. 
> 
> Regards Gary
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