New Accelerometer Supplier Could Be Causing Incorrect iPhone 5s Level and Compass MeasurementsA 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. 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.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. Recent Mac and iOS Blog Stories • Samsung's Request to Delay Investigation of Apple-Nokia Patent License Leaks Denied • Olloclip Releases New Clip-On iPhone Photo Lens with Refined 4-in-1 Capability • Pandora CFO Sees iTunes Radio as 'Credible Threat', Calls iTunes 'Detrimental' to Music Industry • TweetDeck Updated With Docked Tweet Panel, Inline Reply Feature • Square Debuts Square Cash Service, iPhone App • Apple Releases New Java 6 Updates With Enhanced Security, Uninstalls Apple-Provided Java Applet Plug-in • Google Maps Update Improves Navigation, Adds Arabic and Hebrew Support • T-Mobile to End Grandfathered Plans, Implement New Rates
http://www.macrumors.com/2013/10/16/new-accelerometer-supplier-could-be-causing-incorrect-iphone-5s-level-and-compass-measurements/
