sensorfw & Qt is not just UI framework! or Without sensors, there's no IoT

Like it says on the Intel IoT developer site, "Without sensors, there's no IoT".

Because I am the maintainer of QtSensors, I like to inquire about  people's use of sensors and if they use QtSensors. Over the years, I have heard quite often something like, 'Qt is thought of as a UI framework'. *sigh*
 
But Qt is more than just a UI framework and it's use is not dependent on widgets or declarative wizardry. It is used in quite a few middleware components without UI elements. One of those middleware frameworks is Sensor Framework.

Sensor framework is a daemon that uses a plugin system written using Qt for reading various sensors such as accelerometer or light sensors. It was originally developed by Nokia for Harmattan and ran on the N9. It was also used in MeeGo and later included in the Mer Project and on Jolla phones and the ill fated tablet. So it has been released onto a few commercial products.

We looked at it when I was working at Nokia on the project that I still cannot name, but we had decided we would come up with our own solution. Looking back, this was the wrong decision, we should have taken the already proven sensor framework and ran with that. Why? Because it existed and works.

I started maintaining it when I was a privateer (contractor) developer for Jolla. No one else had touched it for some time so I grabbed the few not yet merged bug fixes and added support for libhybris/android libhardware adaptors.

Sensor Framework has support for multiple clients with down sampling for different data rates. It uses dbus for control lines (to start and stop, etc) but sends data through a socket. It also has a working backend in QtSensors.

I noticed that Ubuntu's Unity does nothing to respond when I put this into "tablet mode". I have to manually open the virtual keyboard among other things.

So I thought I could use sensorfw on my Dell 2 in 1. It's one of those converged laptop/tablet devices. It has a few sensors - accelerometer, gyroscope, magnetometer, and lid sensors. One problem... sensorfw does not support lid sensors, or a few other sensors that are around today in IoT (which I will add a bit later). Lid "sensor" might be a bit of a misnomer, as they could be switches but I'd like to think it is more like a hal effect sensor that uses magnets. In any case there are event nodes to use.

First one I chose is to add the lid sensor - to detect when this machine is put into tablet mode, so the UI can better deal with it.

I also noticed that this kernel has support for iio sensor interface for the accel and gyro. Sensorfw only supports sysfs, evdev and hybris interfaces, so I also wanted to add support for that.

I worked on adding iio support first. Well... really just wrote a sensor adaptor plugin. My plugin supports accelerometer, gyroscope and magnetometer, which this device seems to have. I will expand this to support other sensors later, as well as clean it up a bit.

Thanks to QtSensors sensor framework backend, I can make a UI app change with the orientation and lid changes. Better yet, I can create a game that uses accelerometer data like a marble maze game. Or I can upload the data to one of those Node.js data visualization web apps.

And since sensor framework is opensource, others can as well.

snappy sensors

Sensors are an important part of IoT. Phones, robots and drones all have a slurry of sensors. Sensor chips are everywhere, doing all kinds of jobs to help and entertain us. Modern games and game consoles can thank sensors for some wonderfully active games.

Since I became involved with sensors and wrote QtSensorGestures as part of the QtSensors team at Nokia, sensors have only gotten cheaper and more prolific.

I used Ubuntu Server, snappy, a raspberry pi 3, and the senseHAT sensor board to create a senseHAT sensors snap. Of course, this currently only runs in devmode on raspberry pi3 (and pi2 as well) .

To future proof this, I wanted to get sensor data all the way up to QtSensors, for future QML access.

I now work at Canonical. Snappy is new and still in heavy development so I did run into a few issues. First up was QFactoryLoader which finds and loads plugins, was not looking in the correct spot. For some reason, it uses $SNAP/usr/bin as it's QT_PLUGIN_PATH. I got around this for now by using a wrapper script and setting QT_PLUGIN_PATH to $SNAP/usr/lib/arm-linux-gnueabihf/qt5/plugins

Second issue was that QSensorManager could not see it's configuration file in /etc/xdg/QtProject which is not accessible to a snap. So I used the wrapper script to set up  XDG_CONFIG_DIRS as $SNAP/etc/xdg

[NOTE] I just discovered there is a part named "qt5conf" that can be used to setup Qt's env vars by using the included command qt5-launch  to run your snap's commands.

Since there is no libhybris in Ubuntu Core, I had to decide what QtSensor backend to use. I could have used sensorfw, or maybe iio-sensor-proxy but RTIMULib already worked for senseHAT. It was easier to write a QtSensors plugin that used RTIMULib, as opposed to adding it into sensorfw. iio-sensor-proxy is more for laptop like machines and lacks many sensors.
RTIMULib uses a configuration file that needs to be in a writable area, to hold additional device specific calibration data. Luckily, one of it's functions takes a directory path to look in. Since I was creating the plugin, I made it use a new variable SENSEHAT_CONFIG_DIR so I could then set that up in the wrapper script.

This also runs in confinement without devmode, but involves a simple sensors snapd interface.
One of the issues I can already see with this is that there are a myriad ways of accessing the sensors. Different kernel interfaces - iio,  sysfs, evdev, different middleware - android SensorManager/hybris, libhardware/hybris, sensorfw and others either I cannot speak of or do not know about.

Once the snap goes through a review, it will live here https://code.launchpad.net/~snappy-hwe-team/snappy-hwe-snaps/+git/sensehat, but for now, there is working code is at my sensehat repo.

Next up to snapify, the Matrix Creator sensor array! Perhaps I can use my sensorfw snap or iio-sensor-proxy snap for that.