I'm trying to track down a power consumption issue. I know that something out there is using sensors while the device is quietly lying on its back with the screen blank, but I can't tell what.
Is there a way to find out what process is using sensors? (Gravity, in this case.)
Related
Well i have successfully obtained the light value, however, it is EXTREMELY delayed. Approx 3~5 seconds even when using .SENSOR_DELAYED_FASTEST also even when entering 0 as the rate. Its so slow. I have the program check light sensor values upon screen on then change brightness accordingly HOPING it would solve the horrible automatic brightness delay. but after messing around with it, it seems to me that this is simply a flaw in android. It simply cannot update fast enough. I have used getDefaultSensor() but according to android documention this value can be delayed/filtered, but upon reading another post on stackoverflow the getSensorList() and getDefaultSensor() return the same values and that getSensorList() is no different than getDefaultSensor()
The reason for my question is: Is this correct? Is android simply a fail at updating immediatly? its funny cause my Windows MOBILE(not phone) can update immediatly and i loved it. but with all android devices ive seen its the same thing. so is this just a flaw in androids programming? Is there a way for me as an app dev to fix this? or do we have to live with it?
As I know you cannot get it faster. Please take a look on this question and answer: https://stackoverflow.com/a/5060690/1381641
I don't have the solution for your problem, but I do have an explanation for it. The Ambient light sensor has a delay because of the integration time downloads Sensor Box for android from the Playstore.
You will get the hardware ID of your ambient light sensor, then google search it, and you will get a PDF with technical details about that specific model number. Every Android or IOS phone does NOT use the same hardware.
In that PDF, you will get an integration time. It exists to keep the brightness control stable and delayed as well as sensible. If it is low, and you are in a disco your brightness level will keep on flickering. The same for outside, sometimes some shadows make it go up and down if the integration time is low. It will flicker more and will not be stable.
This will also cause harm to the backlight, so instead of taking single values they compile down the values of a big time interval. My integration time was 400ms. This value is sent to the processor, and then the decision is taken.
You could change this value. It is easy, AMD hard boh depends on your expertise like to update this you have to program the ALS unit by opening the phone, connecting a programmer to it, and connecting the pins in the right way. Then sending an 8 bit signal as mentioned in the PDF (if model is programmable).
I'm working with android sensor data. My application use
SensorManager.getRotationMatrixFromVector(
mRotationMatrix , event.values);
and it has been working well until this morning, when the rotation matrix started to send a lot of noise data (Change N to W in a second).
It's not a problem with my code, because on friday was working and no changes have been done. I have used a compass app from the market, and the compass is giving random data.
I have tested my app on another tablet, and it is working well.
Does someone know why is this happening? A problem with the sensor? Does it need a calibration?
I've worked quite a lot with these electronic compasses on mobile phones and its quite possible that there is nothing wrong with your code or sensor.
Instead it could very well be a problem with your environment. There are magnetic fields interfering with the earth's magnetic fields all the time. From electrical equipment interference to the metal structure holding up a building. At the end of the day a compass is just a magnet. If you stand beside a large lump of metal the compass will be attracted to it and point to it rather than the magnetic north pole.
Try this:
Install GPS status
then turn off all filtering (settings... gps & sensors...sensor filtering... no filtering).
Do the calibration (figure of 8 wavy stuff) and then move the phone around your desk.. near monitors, cables, etc. You'll see it go crazy. The information is completely unreliable. I found in the past that moving the phone a few inches to the right completely changed its reading. The same happens with a real compass. Strictly speaking there is no "problem". The device's compass is assigning itself with the strongest magnetic field. Even the magnetic content of nearby rocks can interfere with the compass.
As a further test I've just placed a real (orienteering) compass over my phone which has a compass app installed. The real compass is now pointing everywhere but magnetic North. The two devices are interfering with each other.
So my advice is.. go somewhere in the open, like a park or field, away from any potential interference and power lines, (if you have one bring a real compass to check that the GPS status app is pointing the right way), and see if your compass works as you'd expect.
Extra: The answer from #resus is also important when calibrating. Rotate the phone a few times in each axis. Looks silly but it does calibrate it properly.
Extra 2: Would it be possible/practical to use the compass bearing of your GPS? It would require that the device be moving (walking speed should be fine) but you would not need to worry about any interference. It should give an accurate reading provided your GPS signal is good.
Extra 3: Another thought just occurred to me.. You could try apply a low pass filter to the sensor. This means that the sudden changes in the sensor reading are filtered out .. have a look at this answer. And if that doesn't do a good job there are lots of algorithms on the web for you to choose from.
If you definitely haven't changed anything in your code, and it still works fine on other devices, it would suggest a problem with that particular device.
While your app is running (i.e. the compass is in use), you should be able to wave it in a figure of 8 in order to automatically recalibrate the compass. You should also make sure you aren't standing next to any large lumps of metal etc. that might interfere with readings.
You can override the onAccuracyChanged() method of SensorEventListener to flash up a message to the user when the compass requires recalibration (probably when accuracy drops to SENSOR_STATUS_ACCURACY_LOW).
In my experience of playing with the compass on android phones, they can be pretty unreliable...
If your application work on another tablet and other compass application do not work on your device, this is probably due to a bad calibration.
As said in the post above, to make the calibration, wave your device in a figure of 8. I just want to add that you should do it for EACH axis. This should fix your problem.
If it is not a calibration error, as some people have already answered, it is possible that the compass had gone through a magnetic field and now it is desmagnetized, so it is not working properly.
Where do you usually keep the tablet? Could it be that it was near big servers or magnets?
You should check the compass just in case, talk to to android's tech support.
Hope it helps.
I think the question was if calibration could be done without sending any data to compass. Because not everybody says that the compass is calibrated as shown in this video: https://support.google.com/maps/answer/6145351?hl=en and obviously you can not do anything else than advise the user to calibrate before using the program or when you get too much changes.
For example going left and right 90 degrees in about 25 ms.
Anyway I think it's good to give some seconds to the app before start taking data, because it gives some unstable values (too high and low in short time without movement) at the app loading moment.
Just let the handler onSensorChanged() coded with a conditional, and start a thread on the onCreate() handler, which will set a boolean to true, after some seconds.
Then you start to capture data on the onSensorChanged() handler.
Also this thread can help to detect the sensor accuracy, and then you can popup: In Android can I programmatically detect that the compass is not yet calibrated?
I know because I am building a robot using the compass of the smartphone, and I'm having this experience. So, if you are making a robot, make sure to give an spaced place between electronics and hardware to the smartphone, but remember that it's on any compass: electromagnetic fields can be altered by metals so heavily.
Nowadays I have the luck of developing a robot with an HMC-5983 and an MPU-6050, which can be calibrated by using its libraries with Arduino.
That code is compatible/portable to other uController but for not also so easy for smartphones, I guess that the offsets needed for calibrating the compass, the gyro and the accelerometer are inside some internals of Android, not available in the SDK.
I answered before thinking that maybe calibration was only for some devices, but realized that must be as I said before.
So, if playing with robots its possible, I mean it's also easy, but when using an smartphone maybe some custom firmware as CyanogenMod would bring the possibility of investigating the way of setting that offsets, but more important to run some program ported from sketch (following its concept only) to get them first ...
So, good luck ! What is also true, is that in both devices (smartphone and my robot) it's need to move them for them to get working well, as I showed you in the video of latest answer, also helpful on robots.
Good luck and a lot of fun with those things, are very powerful.
I am currently working on an app that utilizes the light sensors to perform a task in my service. I used the examples from this site as my base:
Android Light Sensor
The sensors work perfectly when my tablet is plugged into the computer to debug. However, if I run the same code without it being plugged in, the response is super slow, and some times never triggers at all.
Can anyone suggest why the performance is hindered when the device is by itself?
EDIT:
I SHOULD HAVE NOTED THAT I AM TRYING TO READ THE SENSOR WITH THE DEVICE OFF. I FOUND THAT THE PROBLEM WAS THAT THE SENSOR WAS SHUTTING DOWN WHEN THE DEVICE SLEPT. PLEASE SEE MY ANSWER BELOW.
Thanks,
josh
Sometimes this is just a device issue, many have been reported as acting slow to light/proximity sensors. As far as the anomaly of the sensors responding normally when it is plugged in; maybe your device sensors simply respond faster when there is a power source.
I'd say look through your options with changing the rate
In:
https://developer.android.com/reference/android/hardware/SensorManager.html
rate rate of events. This is only a hint to the system. events may be received faster or slower than the specified rate. Usually events
are received faster. The value must be one of SENSOR_DELAY_NORMAL,
SENSOR_DELAY_UI, SENSOR_DELAY_GAME, or SENSOR_DELAY_FASTEST.
So I would imagine adding SENSOR_DELAY_FASTEST may help you.
Also, I refer you to Android SENSOR_DELAY_FASTEST isn't fast enough post.
I found that the cause of the trouble was the device shutting the CPU down, which resulted in delay or non-reading of the light sensor.
Adding a partial wake lock did fix the problem, but at the cost of high battery usage. If anyone has any suggestions as to how I can continue monitoring the light sensor with the device off without the Wake Lock I would greatly appreciate it.
I'm making an application that works as a compass..
I'm using the accelerometer and the magnetic field sensors to compute the azimuth angle through, sensor.getOrientation().
I'm searching for something that can improve the magnetic field sensor accuracy, since I'm getting it state of accuracy as UNRELIABLE!
Any one knows anything about this?I'm looking for something that can be either hardcoded or for instance just physically moving the phone until it gets calibrated!
This is not a final answer (I don't know anything for sure), but my understanding from online posts is that waving the phone around in a figure of 8 a few times while the compass is in use is supposed to trigger automatic recalibration. This is what the google maps app suggests, for example. I don't know whether this is dependent on application functionality (something in maps that detects the waving by accelerometer and triggers a recalibration), or something in the android stack, or something specific to per-phone implementations. Try it and see!
Eg discussion: http://androidforums.com/epic-4g-support-troubleshooting/217317-cant-get-compass-calibrate.html
This reference appears to suggest this per-axis / figure-8 rotation process is built-in functionality: http://m.eclipsim.com/gpsstatus/
And here another article that claims this is built-in functionality, and that you don't even need to be running a compass-consuming app for the recalibration to work: http://www.ichimusai.org/2009/06/20/how-to-calibrate-the-htc-magic-compass/
Just a few points
The figure 8 motion works sometimes and not others, I have no idea why, they really need to have some kind of code based way to check if the 8 motion worked (Assuming that the physical motion is actually required)
They also need a way to detect that calibration is required, I looked at the code for the accuracy output (the unreliable constant) and once they send it to you they will not send it again, so for instance if you calibrate but then come within a strong magnetic field it will not resend (not sure why they did that)
One not completely reliable way to detect ongoing issues is that you can also use the magnetic sensor output and do something like field=sqrt(x*x+y*y+z*z) and check that field falls between say 25 and 65 and then ask the user to calibrate if it does not.
The bottom line after testing 18 phones is that I would never depend on a Android based compass with the current crop of phones, accuracy would always be in question.
I have also found even if you are lucky and have a fairly reliable phone you can never be sure that it's calibrated without checking it against a real compass, which kind of defeats the purpose.
NOTE: On a lot of the mis-behaving phones we have found that the sensor writes a calibration file and a tmp file with the same name. If you delete those files and re-boot the phones the calibration file is recreated with zero'd values and the cold start and general calibration problems resolve themselves.
The bad news is that they are stored in /data/misc and require root privileges to get at (thanks Google & Sensor mfg!) so even though I suspect this would solve a lot of problems for a lot of developers it just is not viable from a marketplace app perspective.
I am developing for Android. I'm using Titanium Alloy as development tool with the Titanium Geolocation module.
I have only tested 2 devices [Galaxy Note and S4] against a commercial magnetic compass. Following a calibration process [tilt along the 3 axis] and using 2 different compass apps and the app I'm working on, the Android compass seems accurate enough for basic use ... correlation was good enough for my purpose anyway. I also found the device compass reading to be very sensitive to other magnetic and electrical field interference ... initial mistake I made was to use the compass feature whilst device was in a device protector with a magnetic closure facility [quite common on tabs] ... this interference is particularly strong. I thus need to suggest to users of my app to remove device protectors, keep device free of other electronics and then do standard calibration before initializing the app.
Another option is:
Go To sensors menu: #*0#*
Then if you see a red line in Magnetic Sensor section and a Need for Calibration you should recalibrate your compass.
How;
According those guys;
Turn the Samsung Galaxy Mini S5 around all of its axes until the red
line in the black circle changes color from red to blue. You can also
run through a motion that follows the shape of an 8. It may be that
several attempts are needed to calibrate the compass...
I need to perform power measurements for android applications. I tried "powertutor" and it gives the power consumption per every application. Yet, I don't know how accurate its readings are. Does anyone know how accurate it is?
Also, I have used the DDMS to profile the android application. I obtain the processes as memory info about it. Is there a way that i can know the power consumption per process in Android? (some rough estimation?) or is it impossible?
I really need to perform "power" profiling for android applications but I don't know how.
In my academic research for measuring power consumption on Android, we use a power supply hooked up to the phone's battery terminals that outputs the voltage and current to a PC. Measure without the app to get a baseline and then compare against measurements with the app running. It's not extremely accurate, but it's the best way we know how.