Support for HTU21D

[GoogleCodeExporter]

WebIOPi version used?
=> 0.7.0

Python version used?
=> 3

Distro used? (WebIOPi has only been tested on Raspbian Wheezy)
=> Raspbian Wheezy

Raspberry Pi board revision? (1 or 2)
=> 2

Hello,
I intend to use a combined temperature-humidity sensor, named HTU21D (see: 
https://www.sparkfun.com/products/12064). I managed to get it working, and I 
made a driver, based on hytXXX.py from repository. Actually my next step is to 
make an integration test into webiopi itself, but I don't know how to proceed:
How can I register my driver, how where should I put it? 
I suppose I will need to add it to the DRIVERS dictionary in 
python/webiopi/devices/sensor/__init__.py and I need to put my driver in that 
folder, but that's only the source, it won't affect the installed version... 

Of course, if it's working as expected, I will submit to share it with the 
community.

Oh, and you all made a great job with this framework!

Thank you

Original issue reported on code.google.com by zoltan.z...@gmail.com on 1 Apr 2014 at 8:39

[GoogleCodeExporter]

I have successfully done with integration test. See attached driver. Feel free 
to include it in the next version.

Original comment by zoltan.z...@gmail.com on 1 Apr 2014 at 9:15

Attachments:

• htu21d.py

[GoogleCodeExporter]

Hi,

if you want to check the technical WebIOPi interation, follow these steps:

- Delete lines 1-2 and 131-136

- Change the I2C init calls to the following as I2C address of the chip cant't 
be changed

....
    def __init__(self):
        I2C.__init__(self, 0x40)

- the last two lines of .../sensors/__init__.py should be changed to:

DRIVERS["vcnl4000"] = ["VCNL4000"],
DRIVERS["htu21d"] = ["HTU21D"]

- put your driver into the directory .../sensors

- cd to the "root" directory of your WebIOPi installation and exceute

sudo ./setup.sh skip-apt

to update the Python packages

- add this line to a WebIOPi config file in the [DEVICES] section

myhtu = HTU21D

- stop the WebIOPi daemon if it is running
- start WebIOPi in interactive + debug mode mode using the config file from 
above

sudo webiopi -d -c pathToYourConfigFile

and watch the console outputs if errors occur. If no errors occur, point a 
browser to the WebIOPi device monitor and look if your device shows up with the 
name from the config file and shows a temp and humidity value

DONE

Two final remarks:

1. You mention and credit the original source of the driver. I looked there but 
at the GitHub site there is no official hint about the licensing of that code. 
While this may be a bit paranoid, but it would be better if there were some 
official statement about the licensing, maybe you contact the original 
developer and ask him. Just being public does not formally mean that everyone 
can reuse it ... be warned.

2. Its completely up to Eric as the owner of WebIOPi if he wants (and if he 
does, at what time it will be) to integrate your driver or not, I just gave you 
some hints how to prepare and do it technically.

Thanks for your efforts.

Andreas

Original comment by andreas....@googlemail.com on 2 Apr 2014 at 11:14

[GoogleCodeExporter]

Thank you for your comments.
I will follow your suggestions.
I will contact Jay Wineinger, but as most of the relevant part of the code was 
rewritten (you can compare them) during adaptation to WebIOPi, I wouldn't call 
it "a reuse", nor a copy. I have considered myself your thoughts, but I decided 
to include him as credit. Still, this is legal stuff... :)

Original comment by zoltan.z...@gmail.com on 2 Apr 2014 at 11:43

[GoogleCodeExporter]

I got Jay's written permission.

Original comment by zoltan.z...@gmail.com on 2 Apr 2014 at 12:59

[GoogleCodeExporter]

Small mistake, there was a comma too much, should be

DRIVERS["vcnl4000"] = ["VCNL4000"]
DRIVERS["htu21d"] = ["HTU21D"]

I want to update this to avoid confusing others that may read my feedback above.

Original comment by andreas....@googlemail.com on 11 Apr 2014 at 11:46

[GoogleCodeExporter]

Here is the final version. I have compared the result to measurements made with 
a dedicated devices, and they are good. Still, if someone needs precision, 
calibration has to be done for the individual sensors, and correction might 
also be used.

Original comment by zoltan.z...@gmail.com on 14 Apr 2014 at 6:01

Attachments:

• htu21d.py

[GoogleCodeExporter]

Thanks for the driver some additional improvement possibilities ... (don't take 
me wrong, this just has to do with coding style, but not with functionality, 
but unique coding syles make code reading for others simpler and we are here in 
open source, so reading code of others is one of the basics, so its like making 
something that is already good, fully perfect :-))

- Method names of WebIOPi drivers are in camelCase, so get_rel_humidity() 
should become getRelHumidity()
- Methods that are only to be called locally within a class (hierarchy) but not 
from outside should be surrounded by __. This is also good Python coding 
convention. To have a rule for this, all methods of devices that make sense to 
be called e.g. from a WebIOPi custom script should be without the __, all 
others should have them. In your case, it looks like all methods are locally, 
maybe reset() could be a candidate to be called from outside but you call it 
each time you calculate a value so this may be unnecessary
- You have some declarations and methods to set the resolution but it looks its 
never used for now, how is this thought to be used? Maybe an init-parameter to 
set the resolution via config-file may make sense? In this case, the method 
setResolution could be also a external candidate. However, it might have to be 
changed because it uses and index within the internal object RESOLUTIONS 

Andreas

Original comment by andreas....@googlemail.com on 16 Apr 2014 at 11:12