[collectd] Modbus plugin seems to read garbage values

[Gerry Demaret]

I've been playing with the modbus plugin to read the values from a
Schneider Electric PowerLogic EGX100. I'm using Debian testing which
has collectd 5.1.

First tries resulted in segmentation faults when I would enable the
modbus plugin. Some searches later, I found other people having the
same problem and ended up applying their patches to src/modbus.c.
Just in case, my modbus.c file can be found here:

   http://gerry.safehex.be/tmp/modbus.c-patch

I recompiled the package and it no longer segfaults, but it still
doesn't work properly.

The values in the rrd files seem to be completely wrong, it says I'm
using -17.9A and my power consumption is 9GWh. Since there isn't much
to configure in collectd, I don't know what the problem might be. Does
anyone have a pointer as to what I should look into?

This is the relevant part of my config:

> LoadPlugin modbus
>
> <Plugin modbus>
> 	<Data "current-phase1">
> 		RegisterBase 3000
> 		RegisterType float
> 		Type current
> 		Instance "phase1"
> 	</Data>
>
> 	<Data "current-phase2">
> 		RegisterBase 3002
> 		RegisterType float
> 		Type current
> 		Instance "phase2"
> 	</Data>
>
> 	<Data "current-phase3">
> 		RegisterBase 3004
> 		RegisterType float
> 		Type current
> 		Instance "phase3"
> 	</Data>
>
> 	<Data "voltage-l1">
> 		RegisterBase 3028
> 		RegisterType float
> 		Type voltage
> 		Instance "voltagel1"
> 	</Data>
>
> 	<Data "voltage-l2">
> 		RegisterBase 3030
> 		RegisterType float
> 		Type voltage
> 		Instance "voltagel2"
> 	</Data>
>
> 	<Data "voltage-l3">
> 		RegisterBase 3032
> 		RegisterType float
> 		Type voltage
> 		Instance "voltagel3"
> 	</Data>
>
> 	<Data "power-totalactive">
> 		RegisterBase 3060
> 		RegisterType float
> 		Type power
> 		Instance "totalactive"
> 	</Data>
>
> 	<Data "power-totalreactive">
> 		RegisterBase 3068
> 		RegisterType float
> 		Type power
> 		Instance "totalreactive"
> 	</Data>
>
> 	<Data "power-totalapparent">
> 		RegisterBase 3076
> 		RegisterType float
> 		Type power
> 		Instance "totalapparent"
> 	</Data>
>
> 	<Host "hq.tigron.net">
> 		Address "10.2.0.99"
> 		Port "502"
> 		Interval 10
>
> 		<Slave 2>
> 			Collect "frequency"
> 			Collect "current-phase1"
> 			Collect "current-phase2"
> 			Collect "current-phase3"
> 			Collect "voltage-l1"
> 			Collect "voltage-l2"
> 			Collect "voltage-l3"
> 			Collect "power-totalactive"
> 			Collect "power-totalreactive"
> 			Collect "power-totalapparent"
> 		</Slave>
> 	</Host>
> </Plugin>

Thanks,

Gerry.