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Re: Advice of best xAP structure for OWL Electricity Monitor
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Hi Marcus....
First of all how and what you present is really your choice so the
encoded data and displaytext= is fine if that's how you want to do it.
You could of course split it across several endpoints as well if you
prefer.
Although not very tidy you could add your own parameters within the
BSC message should you wish , perhaps presenting your extra information
as data= or even a series of parameters, or as you say you can create
your own schema to present more info in one message. The latter is
perhaps better.
I wouldn't worry too much about the packet length as you have a lot
of headway in a UDP packet, you can even delimit decimal values if you
wish text=1,2,3,45,666 but I'm thinking it maybe better to present
each as an individual parameter in the body.
Amps=1.23
Volts=235
etc
One thing you should change for the BSC schema is to create an
endpoint (sub address) and don't use the main application address (which
ends in 00). So change the end digit of the UID and create a sub
address .. something like..
UID=FF111101
source=MJW.U-Mon.MW_Laptop:KWHr
Now if you later want to add more info presented in different BSC
messages you can just create more sub addresses and change the UID.
Remember BSC is a two way schema so you must receive and respond
(with a xapBSC.info) to a xAPBSC.query message targeted at your endpoint
(and any wildcarded variant of it's address).
I note there is no hop= parameter in the header (it's mandatory) ,
but I'm thinking that might just be an omission in the posting
Using your own schema to create a way of querying a database is
absolutely allowable - you can use xAP just as you wish. Actually this
same requirement comes up quite frequently in weather applications -
high/low figures over minute/hour/day/month/year etc. Before you ask
...there is no standard schema for this query approach.
You could also create several BSC reporting end nodes for the same
info (KWHr) but over the different periods you wish to use eg a 2 minute
node with the peak or average consumption. A little untidy but workable.
source=MJW.U-Mon.MW_Laptop:KWHr.2min.peak
source=MJW.U-Mon.MW_Laptop:KWHr.2min.average
source=MJW.U-Mon.MW_Laptop:KWHr.30min.peak
source=MJW.U-Mon.MW_Laptop:KWHr.30min.average
I'll add MJW to the list of xAP vendor ID's.
Cheers Kevin
On 01/04/2011 16:32, Marcus Warrington wrote:
>
> I've just knocked up a little program to extract the current
> electricity usage (KWh/Amps) from a USB OWL Connect I purchased on
Ebay.
>
> I ended up paying about £7 for the OWL Connect receiver , but
> apparently Tesco were selling these off a few months ago for less than
> a fiver !
>
> I've successfully retrieved the usage information in real time (every
> 6 seconds) but am unsure of the best way or presenting this onto the
> xAP network. Currently the program is obtaining the information and if
> its changed then sending the usage value in a "standard" BSC
event
> format. If nothing changed for 60seconds then its sends an info
> message. I'm using the xAP dll from the mi4 website to handle the xAP
> side of things.
>
> At the moment I'm encoding the usage as a "stream" in Hex
format in
> the "text" key, and presenting it in a human readable form
in the
> displaytext key.
>
> e.g.
>
> {
> v=12
> uid=FF111100
> class=xAPBSC.event
> source=MJW.U-Mon.MW_Laptop
> }
> input.state
> {
> State=on
> text=DC1F447B1F41F4083
> displaytext= 1.18 KWh (0.5 Amps)
> }
>
> The text encoding format I've chosen is hex encoded to keep the down
> the size of the packet and consists of;
>
> 2 chars for supply voltage (DC=220)
>
> 3 chars for Current usage in Amps (1F4 = 500 = /100 = .5amps)
>
> From these 2 pieces of information the client can calculate the KWh
usage.
>
> The next 3 chars are for the currently defined electricity cost i.e.
> 47B = 1147 = 11.47pence per KWh
>
> The next 3 are the minimum Amps used figure (still not sure exactly
> what the OWL is actually reporting with this)
>
> The next 3 are the maximum Amps used figure (still not sure exactly
> what the OWL is actually reporting with this)
>
> The next 2 chars are the Green House Gas figure (008)
>
> And the final single character represents the trend,0=unknown,
> 1=downward,2=neutral,3=upward
>
> I'm also thinking of implementing a custom packet structure instead of
> BSC that will provide more information, such as the last two minutes
> worth of figures or even a query structure to allow a date range
> selection to be return (maybe then used for graphing etc?). I'm not
> sure if this would be considered an abuse the xAP protocol, since its
> actually being used simply to transferring data from a database.
>
> So the question is.... is what I'm doing OK or does anyone think I
> should be doing it differently either for efficiency or best practice
> reasons ?
>
> I'm slightly unsure of the hex encoding since it would only be
> slightly longer to encode in decimal but would be much easier for the
> client to handle (i.e. no Hex to decimal conversion)
>
> Also do I need to register "MJW" as an official xAP vendor
name?
>
> Regards
>
> *Marcus *
>
>
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Hi Marcus.... <br>
<br>
First of all how and what you present is
really your choice so
the encoded data and displaytext= is fine if that's how you want to
do it. You could of course split it across several
endpoints as
well if you prefer.<br>
<br>
Although not very tidy you could add your own
parameters within
the BSC message should you wish , perhaps presenting your extra
information as data= or even a series of parameters, or as you say
you can create your own schema to present more info in one message.
The latter is perhaps better.<br>
<br>
I wouldn't worry too much about the packet
length as you have a
lot of headway in a UDP packet, you can even delimit decimal values
if you wish text=1,2,3,45,666 but I'm thinking it maybe
better to
present each as an individual parameter in the body.<br>
<br>
Amps=1.23<br>
Volts=235<br>
etc<br>
<br>
<br>
One thing you should change for the BSC
schema is to create an
endpoint (sub address) and don't use the main application address
(which ends in 00). So change the end digit of the UID and create
a
sub address .. something like..<br>
<br>
<span style="font-size: 12pt;">UID=FF111101<br>
source=MJW.U-Mon.MW_Laptop:KWHr<br>
<br>
Now if you later want to add more info presented in different
BSC messages you can just create more sub addresses and change the
UID.<br>
<br>
Remember BSC is a two way schema so you must receive and respond
(with a xapBSC.info) to a xAPBSC.query message targeted at your
endpoint (and any wildcarded variant of it's address).<br>
<br>
I note there is no hop= parameter in the header (it's mandatory)
, but I'm thinking that might just be an omission in the
posting<br>
<br>
Using your own schema to create a way of querying a database is
absolutely allowable - you can use xAP just as you wish. Actually
this same requirement comes up quite frequently in weather
applications - high/low figures over minute/hour/day/month/year
etc. Before you ask ...there is no standard
schema for this
query approach. <br>
<br>
You could also create several BSC reporting end nodes for the
same info (KWHr) but over the different periods you wish to use eg
a 2 minute node with the peak or average consumption. A little
untidy but workable.<br>
<br>
</span><span style="font-size:
12pt;">source=MJW.U-Mon.MW_Laptop:KWHr.2min.peak<br>
</span><span style="font-size:
12pt;">source=MJW.U-Mon.MW_Laptop:KWHr.2min.</span>average<br>
<span style="font-size:
12pt;">source=MJW.U-Mon.MW_Laptop:KWHr.30min.peak<br>
</span><span style="font-size:
12pt;">source=MJW.U-Mon.MW_Laptop:KWHr.30min.</span>average<br>
<span style="font-size: 12pt;"><br>
I'll add MJW to the list of xAP vendor ID's.<br>
<br>
<br>
Cheers Kevin<br>
<br>
</span> On 01/04/2011 16:32, Marcus Warrington wrote:
<blockquote
cite="mid:38DB8F60848A594CBF1B5BE0732099781B173C52@xxxxxxx"
type="cite">
<span style="display: none;"> </span>
<div id="ygrp-text">
<p>
</p>
<div class="WordSection1">
<p class="MsoNormal"><span>I’ve just
knocked up a little
program to extract the current electricity usage
(KWh/Amps) from a USB OWL Connect I purchased on
Ebay.<o></o></span></p>
<p class="MsoNormal"><span>I ended up paying about
£7 for
the OWL Connect receiver , but apparently Tesco were
selling these off a few months ago for less than a
fiver !<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p class="MsoNormal"><span>I’ve
successfully retrieved the
usage information in real time (every 6 seconds) but
am unsure of the best way or presenting this onto the
xAP network. Currently the program is obtaining the
information and if its changed then sending the usage
value in a “standard” BSC event format. If nothing
changed for 60seconds then its sends an info message.
I’m using the xAP dll from the mi4 website to handle
the xAP side of things.<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p class="MsoNormal"><span>At the moment
I’m encoding the
usage as a “stream” in Hex format in the
“text” key,
and presenting it in a human readable form in the
displaytext key.<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p
class="MsoNormal"><span>e.g.<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p class="MsoNormal">
<span style="font-size: 12pt;">{<br>
v=12 <br>
uid=FF111100 <br>
class=xAPBSC.event <br>
source=MJW.U-Mon.MW_Laptop <br>
} <br>
input.state<br>
{<br>
</span><span style="font-size:
12pt;"> State=on<br>
text=DC1F447B1F41F4083<br>
displaytext= 1.18 KWh (0.5 Amps)<br>
} <br>
</span><span><br>
The text encoding format I’ve chosen is hex encoded to
keep the down the size of the packet and consists of;<br>
<br>
<o></o></span></p>
<p class="MsoNormal"><span>2 chars for supply voltage
(DC=220)<o></o></span></p>
<p class="MsoNormal"><span>3 chars for Current usage
in
Amps (1F4 = 500 = /100 = .5amps)<br>
<br>
<o></o></span></p>
<p class="MsoNormal"><span>From these 2 pieces of
information the client can calculate the KWh usage.<br>
<br>
The next 3 chars are for the currently defined
electricity cost i.e. 47B = 1147 = 11.47pence per
KWh<o></o></span></p>
<p class="MsoNormal"><span>The next 3 are the minimum
Amps
used figure (still not sure exactly what the OWL is
actually reporting with this)<o></o></span></p>
<p class="MsoNormal"><span>The next 3 are the maximum
Amps
used figure (still not sure exactly what the OWL is
actually reporting with this)<o></o></span></p>
<p class="MsoNormal"><span>The next 2 chars are the
Green
House Gas figure (008)<o></o></span></p>
<p class="MsoNormal"><span>And the final single
character
represents the trend,0=unknown,
1=downward,2=neutral,3=upward<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p class="MsoNormal"><span>I’m also
thinking of
implementing a custom packet structure instead of BSC
that will provide more information, such as the last
two minutes worth of figures or even a query structure
to allow a date range selection to be return (maybe
then used for graphing etc?). I’m not sure if this
would be considered an abuse the xAP protocol, since
its actually being used simply to transferring data
from a database.<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p class="MsoNormal"><span>So the question
is…. is what
I’m doing OK or does anyone think I should be doing it
differently either for efficiency or best practice
reasons ?<o></o></span></p>
<p class="MsoNormal"><span>I’m slightly
unsure of the hex
encoding since it would only be slightly longer to
encode in decimal but would be much easier for the
client to handle (i.e. no Hex to decimal conversion)<br>
<br>
<o></o></span></p>
<p class="MsoNormal"><span>Also do I need to register
“MJW” as an official xAP vendor
name?<o></o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p
class="MsoNormal"><span><o> </o></span></p>
<p
class="MsoNormal"><span>Regards<o></o></span></p>
<p class="MsoNormal"><span
lang="EN-US"><o> </o></span></p>
<p class="MsoNormal"><b><span
style="font-size: 10pt;
color: rgb(84, 141, 212);">Marcus
</span></b><o></o></p>
<p
class="MsoNormal"><o> </o></p>
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