New Accelerometer Supplier Could Be Causing Incorrect iPhone 5s Level and Compass Measurements

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A new supplier for the accelerometer part in the iPhone 5s could be causing incorrect level and compass measurements in the new device, an issue that was first noticed earlier this month.

RealityCap CEO Eagle Jones read into the Chipworks teardown of the iPhone 5s (via Gizmodo) and noticed that the phone uses the Bosch Sensortech BMA220 as its accelerometer. The iPhone 5, for example, used an accelerometer from STMicroelectronics.

incorrectlevel.png
iPhone 5s and level, courtesy Gizmodo​
Both devices have similar consistency in measurement, but the Bosch device has a larger measurement 'bias'. The end result, as Jones notes, is that the new accelerometer has a different 'zero-g offset' which would need to be compensated for in software.
The second key spec for accelerometers is the zero-g offset, or bias. This indicates the range for a roughly constant offset that will be added to every output sample of data due to manufacturing variance. This can also change over time due to mechanical stress or temperature variation. This is where we find the problem: the typical bias for the ST part is +/- 20mg, while the Bosch part lists +/-95mg. This almost 5x greater offset range is confirmed by our measurements, and is absolutely consistent with the failures being reported by users and the media. Specifically, a +/- 20mg offset range would translate to around a +/-1 degree accuracy range in tilt detection, and a +/-95mg offset translates to +/-5 degrees in tilt.
Click to expand...
He goes on to note that developers can compensate for the increased offset because it is unlikely to change significantly from one measurement to another, though Apple could do a system-wide fix at the OS level to ensure accurate measurements in the future.

Article Link: New Accelerometer Supplier Could Be Causing Incorrect iPhone 5s Level and Compass Measurements
 
Article Link
https://www.macrumors.com/2013/10/16/new-accelerometer-supplier-could-be-causing-incorrect-iphone-5s-level-and-compass-measurements/
Not sure how this type of things gets by testing, just since it seems to be a problem that affects nearly every new iPhone 5s. Since it's a new part, you would think there would even be more testing than usual.
 
The problem exists with the iPhone 5 and iOS 7 also!
Compass and level are not accurate !!!!!
Making them worthless.
 
It's amazing how someone can figure out what the problem is in a few weeks, while all of Apple engineering let this one get by them. Developers should not have to "compensate" their apps because of poor Apple QC.
 
This is exactly why it shouldn't just be compensated by the same amount in every device with an update, but rather a simple "calibrate" button should be added that prompts you to use a real level and calibrate the device. Since, as they said, the bias changes over time, you probably want to recalibrate it from time to time, so it's a useful feature to add.

Every scale, measurement device, etc… even the most professional ones all have the ability to be calibrated. No one's expecting the iPhone to be accurate for this type of thing, which is one more reason to add a calibration feature.
 
If anybody has this problem please try to open your compass app en see if the middle cross is out of alignment...

Cant test this my self.
 
KPOM said:
Is there any new information here that isn't on the 70+ page thread in the iPhone forum?
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Maybe raise awareness?

Maybe other websites will echo this story?

Maybe it will cause a big enough ripple to make Apple say something about it?
 
KPOM said:
Is there any new information here that isn't on the 70+ page thread in the iPhone forum?
Click to expand...

I don't know, but if not... as someone who doesn't want to have to read through 70+ pages of comments in a forum to get this information, I'm glad to have a summary presented here.
 
It certainly is nice to know that this should be an easy software fix. Would've been really disappointing for people to know that they are just stuck with unfixable faulty hardware in their brand new phone.

Apple should be able to implement something at the system level, perhaps a tweak of the API such that devs don't have to worry about adjusting their code, right?
 
Well this proves its a hardware issue, caused by what seems to be Apple switching sensors due to size contstraints. (Another article posted that this Bosch sensor is smaller.) Now the question is can Apple come up with a permanent software fix. I really don't want to have to calibrate every single time I use the level, play a game, take a pano photo, etc......
 
Ivan0310 said:
It certainly is nice to know that this should be an easy software fix. Would've been really disappointing for people to know that they are just stuck with unfixable faulty hardware in their brand new phone.

Apple should be able to implement something at the system level, perhaps a tweak of the API such that devs don't have to worry about adjusting their code, right?
Click to expand...

Well they wont change the hardware supplier for the accelerometer so it will have to be a firmware change. It would be nice to know when
 
Ivan0310 said:
It certainly is nice to know that this should be an easy software fix. Would've been really disappointing for people to know that they are just stuck with unfixable faulty hardware in their brand new phone.

Apple should be able to implement something at the system level, perhaps a tweak of the API such that devs don't have to worry about adjusting their code, right?
Click to expand...

It sucks this problem exists in the first place, but I agree... this is good news, if true.
 
Here's an idea for the new SVP of Retail.

Set up a table at all Apple Stores worldwide. Have the surface of the table calibrated to be dead flat in all directions.

Send out an email suggesting that interested users can come in and calibrate their iPhones against a known flat surface.

And while you're there, you can pick up a new iPad and a Macbook Air.

ft
 
This story made me go in and check the level out on my iPhone 5 running 7.0.2.

Here's what I found: setting the phone on what I believe to be my perfectly level desk, it read "-1 degree". I tried multiple times and got the same result each time.

However, if I tilted the phone ever so slightly so that it read 0 degrees and then let go of the phone and set it back down on my desk untouched, the display continued to read 0 degrees. I repeated this process several times and the result was always the same.

Seems to me like buggy software unless the accelerometer in my iPhone 5 has been messed up since day one. Either way, for the stuff I use a level for, being one degree off won't matter at all (although I saw the earlier stories about 5s's being several degrees off).
 
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