Some of you following my micro-blogging on Twitter might already know about it: In the last few months I have been busy developing a new application. What initially just started out as a re-write of the user interface of Quasar Media Player has turned into a completely new application called QuasarMX. It is based on the very core of Quasar Media Player but stripped of all the legacy and third-party code. The completely new UI is based on Qt Quick / QML, a new technology which simplicity and elegance I fell in love with over the past year. For me QuasarMX also marks the start of two experiments:
1. How many platforms and operating systems can I port my app to?
2. Is there any commercial viability at all in publishing the software to various app stores (Nokia Ovi store, Android Market etc.) ?
The first experiment is important to me. Now that Nokia put the Qt project into open governance, the Qt community has the unique opportunity to extend primary platform support to Android, iOS and possibly even Windows Phone 7, thus extending the possible market cap and audience for mobile apps based on Qt dramatically. This experiment is largely about experiencing first hand what changes are required to get my application running on these platforms and as a matter of fact what needs to be done in projects like Necessitas (Qt on Android) to make that goal happen.
As for the second experiment I am actually just interested in getting to know the mechanics of the various app stores. I am pretty confident that there is little to no money to be made from yet another music player app. Yet, it is still interesting to see what happens, what works and what not, especially in regards to future apps.
In July Nokia accepted my application and invited me into the Qt Ambassador program. As part of this program Nokia loaned a N950 developer device to me, which I extensively used to develop and test the Harmattan UI for QuasarMX. The new user interface is very much inspired by the simplicity of the MeeGo Harmattan Swipe UI.
FHEM, the amazing home-automation server software, already has support for several sensors, meters and switches produced by ELV. In October 2010 I bought two meters, ESA1000WZ and ESA1000GAS for my house in the hope that FHEM would support them. Unfortunately it did not (at the time). I quickly found some hints that somebody, namely Gerd K., was working on adding support. So I contacted him and a day later received his module for testing. In the meantime eager in anticipation I was hacking away, duplicating the existing EM1000 extension and customizing it to read the raw strings coming from my Busware.de CUL 868 MHz USB adapter. While I got the power meter’s values (ESA1000WZ) figured out pretty quickly, it was a bit more involving to get correct readings from the gas meter (ESA1000GAS). Unfortunately Gerd’s code did not include support for the gas meter, so I emailed him my changes, but sadly never received feedback.
So today I am releasing my code on a works-for-me basis:
If you are using FHEM 5.0:
Copy 19_CUL_ESA.pm and all .gplot files to your FHEM directories.
Sadly adding autocreate support and extending the CUL module to understand the raw message strings requires patching. Check cul_esa-for-fhem-5.0.patch to patch the files. This was diffed against the Debian package of FHEM 5.0. The very same version of FHEM as tar.gz has some differences in the sourcecode and some files missing. I contacted the author of FHEM about this issue but he has not updated the packages yet. So if you run into issues here it is probably due to these differences.
Here are some notes in German I made while developing the module, mostly concerning the different behavior of the ESA1000GAS compared to the ESA1000WZ:
Der ESA1000GAS mit dem ESA1000Z-Messgerät verhält sich leider anders als das ESA1000WZ, sodaß ich wieder die Korrektur-Faktoren einbinden mußte.
Ich konnte nicht herausfinden, wozu der übermittelte Tick beim ESA1000Z dient. Zwar ändert sich dieser mit geänderter Zählerkonstante, allerdings ergibt der Wert im Zusammenhang mit den von der Einheit übermittelten Werten keinen Sinn, sodaß ich hier direkt mit der Zählerkonstante multipliziere, um die Kubikmeter zu erhalten, und dann zusätzlich noch mit dem Umrechnungsfaktor (bei der EWE ergibt sich dieser aus der Zustandszahl * Brennwert Hs) multipliziere, um die Kilowattstunden aus der Gasmenge zu erhalten.
Leider ändern sich damit die Parameter bei der Definition:
Ich habe ebenfalls noch einen Durchschnittswert in Kilowatt implementiert, sodaß man die Durchschnittleistung einigermaßen sinnvoll in einem Diagramm darstellen kann. Hier gab es allerdings bei meinem Drehstromzähler Probleme mit Unterabtastung, weil sich die Drehscheibe bei geringem Verbrauch zu langsam dreht, sodaß das Meßgerät zwischendurch schon Nullwerte zurückmeldet, weil kein Impuls eingegangen ist. Dafür habe ich einen entsprechenden Schwellenwert bei der Berechnung des Durchschnittswertes implementiert. Nicht schön, funktioniert aber für meine Zwecke.