Fix warning about always empty value

[RobBuijs]

P1 on my slimme meter is always complaining

[P1] warning: 1-0:99.97.0: ignoring unknown value ()

With this simple patch it isn't anymore.

[ebaauw]

Sorry, that’s like taking the the warning light.

What does this value mean? Is there any unit associated with it? What DSMR version does your meter support?

[RobBuijs]

Haha, valid points.

OBIS Reference "1-0:99.97.0.255" has value "Power Failure Event Log (long power failures)". Not sure how to figure out the DSMR version. It's a new slimme meter, placed a couple of weeks ago. Could also explain why the field is empty - no power failures yet.

It's a bit verbose, but this is a sample telegram.

ISK5\2M550E-1013
1-3:0.2.8(50)
0-0:1.0.0(201126123723W)
0-0:96.1.1(4530303533303037353134323331343139)
1-0:1.8.1(000056.179*kWh)
1-0:1.8.2(000083.425*kWh)
1-0:2.8.1(000000.000*kWh)
1-0:2.8.2(000000.000*kWh)
0-0:96.14.0(0002)
1-0:1.7.0(00.759*kW)
1-0:2.7.0(00.000*kW)
0-0:96.7.21(00008)
0-0:96.7.9(00002)
1-0:99.97.0()
1-0:32.32.0(00003)
1-0:32.36.0(00001)
0-0:96.13.0()
1-0:32.7.0(239.4*V)
1-0:31.7.0(003*A)
1-0:21.7.0(00.742*kW)
1-0:22.7.0(00.000*kW)
!85C4

[ebaauw]

Not sure how to figure out the DSMR version 1-3:0.2.8(50)

That’s DSMR v5.0. Same version as the meter they installed in my home.

OBIS Reference "1-0:99.97.0.255" has value "Power Failure Event Log (long power failures)".

Indeed, Homerbridge P1 already supports that. https://github.com/ebaauw/homebridge-p1/blob/af6ab812da0bbadfaf044ac4e7645e2a392b07d3/lib/P1Client.js#L180

1-0:99.97.0()

However, I haven't seen an empty value before. I think it should report at least (0) to indicate the number of power failures. "My" meter reports:

1-0:99.97.0(0)(0-0:96.7.19)

From another user, I got:

1-0:99.97.0(2)(0-0:96.7.19)(180327064111S)(0000000180*s)(190108105923W)(0000002603*s)

Looking at the code, it doesn't like a completely empty value, treating it as unknown. Commit below should fix this.

[RobBuijs]

Yes, That's much cleaner. And it works fine.

I'm curious what my meter will report if there is a power event failure. Can't simulate (or cause) one, so I'll have to wait for that.