Plugwise and Linux
Posted: Sun Dec 07, 2008 11:27 pm
As promised, the stuff required for the power measurement.
<b>Calibration</b>
Each plugwise plug has some calibration information. This information can be found in the plugwise access database (PlugwiseData.mdb)
The values containing calibration information are the following:
- OffRuis
- OffTot
- GainA
- GainB
You can also query the information from the plug itself using the stick.
Let's analyze a calibration request:
The first 4 characters represent the function code, in this case it's the "0026" command for the calibration request.
The next characters represent the mac address of the plug, in this case "00A1100003111AB"
The last 4 characters are the CRC16 code, for an explanation of this see my earlier post.
Let's analyze the calibration response:
Note: the spaces have been included for readability.
The first 4 characters represent the function code, in this case calibration response.
The next string is the mac address.
Now for the interesting part:
- 3F78BD69 represents the GainA value hexadecimal.
- B6FF0876 represents the GainB value hexadecimal.
- 3CA99962 represents the OffTot value hexadecimal.
- 00000000 represents the OffRuis value hexadecimal.
- The last code is (i think) a CRC16 code again, not sure about this one.
I use a function like this in python to convert the hexadecimal values to a "human readable" float or double:
The calibration information is used for a correct reading of the watt usage.
<b>Power information</b>
Power information is read by using the following command:
It needs no explanation that the function code is "0012" the mac adress is the next string etc.
The powerinfo response looks like this:
The first two parts of this need no explanation.
The following explains the codes followed by that:
- 0030 pulse information of 8 seconds reading.
- 0030 pulse information of 1 second reading.
- 0001D62A yet unknown, still trying to figure out.
The pulse information is again hexadecimal. To convert it to a integer I use the following python code:
How to get the watt I hear you asking?
First the pulse information has to be corrected based on the calibration information of the plug, that's done using the following formula:
1.0 * (((pow(value + offruis, 2.0) * gain_b) + ((value + offruis) * gain_a)) + offtot)
Where value is the number of pulses in integer format. pow() is a python for the mathematical power.
If the pulse information has been corrected based upon the calibration information you can go to KWH using the following formula:
(pulses / 1) / 468.9385193
Where pulses is the number of pulses offcourse.
To go to watt you'll simply have to do multiply by 1000.
Long story, I hope it's clear enough.
About the source code:
I will release this as soon as I have some time to cleanup the code a bit (it's a really big mess right now)
--
Maarten Damen
www.maartendamen.com
<b>Calibration</b>
Each plugwise plug has some calibration information. This information can be found in the plugwise access database (PlugwiseData.mdb)
The values containing calibration information are the following:
- OffRuis
- OffTot
- GainA
- GainB
You can also query the information from the plug itself using the stick.
Let's analyze a calibration request:
Code: Select all
<ENQ><ENQ><ETX><ETX>002600A1100003111AB7071<CR><LF>The next characters represent the mac address of the plug, in this case "00A1100003111AB"
The last 4 characters are the CRC16 code, for an explanation of this see my earlier post.
Let's analyze the calibration response:
Code: Select all
<ENQ><ENQ><ETX><ETX>0027 00A1100003111AB 3F78BD69 B6FF0876 3CA99962 00000000 EE6D<CR><LF>The first 4 characters represent the function code, in this case calibration response.
The next string is the mac address.
Now for the interesting part:
- 3F78BD69 represents the GainA value hexadecimal.
- B6FF0876 represents the GainB value hexadecimal.
- 3CA99962 represents the OffTot value hexadecimal.
- 00000000 represents the OffRuis value hexadecimal.
- The last code is (i think) a CRC16 code again, not sure about this one.
I use a function like this in python to convert the hexadecimal values to a "human readable" float or double:
Code: Select all
def hexToFloat(self, hexstr):
intval = int(hexstr, 16)
bits = struct.pack('L', intval)
return struct.unpack('f', bits)[0]<b>Power information</b>
Power information is read by using the following command:
Code: Select all
<ENQ><ENQ><ETX><ETX>0012 00A1100003111AB AB43<CR><LF>The powerinfo response looks like this:
Code: Select all
<ENQ><ENQ><ETX><ETX>0013 00A1100003111AB 0030 0030 0001D62A 9863<CR><LF>The following explains the codes followed by that:
- 0030 pulse information of 8 seconds reading.
- 0030 pulse information of 1 second reading.
- 0001D62A yet unknown, still trying to figure out.
The pulse information is again hexadecimal. To convert it to a integer I use the following python code:
Code: Select all
def hexToInt(self, hexstr):
return int(hexstr, 16)First the pulse information has to be corrected based on the calibration information of the plug, that's done using the following formula:
1.0 * (((pow(value + offruis, 2.0) * gain_b) + ((value + offruis) * gain_a)) + offtot)
Where value is the number of pulses in integer format. pow() is a python for the mathematical power.
If the pulse information has been corrected based upon the calibration information you can go to KWH using the following formula:
(pulses / 1) / 468.9385193
Where pulses is the number of pulses offcourse.
To go to watt you'll simply have to do multiply by 1000.
Long story, I hope it's clear enough.
About the source code:
I will release this as soon as I have some time to cleanup the code a bit (it's a really big mess right now)
--
Maarten Damen
www.maartendamen.com
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