Accelerometers
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These are theoretical values. In real life your mileage will vary. | These are theoretical values. In real life your mileage will vary. | ||
| + | == Using the data == | ||
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| + | The ''X'' and ''Y'' values can be used to calculate<ref>Tom Pycke, ''[http://tom.pycke.be/mav/69/accelerometer-to-attitude Accelerometer to pitch and roll]</ref>'' the roll (that is, clockwise rotation) using the ''atan2'' function: | ||
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| + | angle_in_radians = '''atan2'''(''x'', ''y'') | ||
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| + | Similar, ''Y'' and ''Z'' can be used to calculate the pitch. | ||
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| + | == References == | ||
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| + | <small> | ||
| + | <references/> | ||
| + | </small> | ||
[[Category:Development]][[Category:Fremantle]] | [[Category:Development]][[Category:Fremantle]] | ||
Revision as of 21:51, 6 July 2009
Fremantle offers the possibility to play with accelerometers. There is a plan to offer a proper interface for accelerometers in Maemo, but if you want to try out before there are a couple of ways to do it.
See also the related thread in talk.maemo.org.
Contents |
D-Bus
Thomas Thurman (marnanel) has put together a simple demo of an application using accelerometers using the D-Bus interface. You can find sources and .deb up at http://people.collabora.co.uk/~tthurman/sandcastle/
sysfs
Another way is to use the sysfs file information.
/sys/class/i2c-adapter/i2c-3/3-001d/coord
When reading that file you get 3 values X, Y and Z. Values are in mG (milli G). 1000 = 1 G
- On the table face up values are 0, 0, -1000 (face down would read 0, 0, 1000)
- On the table on botton side (landscape): 0, -1000, 0
- On the table on right side (portrait): -1000, 0, 0
- In any other position any mix of those 3 values.
These are theoretical values. In real life your mileage will vary.
Using the data
The X and Y values can be used to calculate[1] the roll (that is, clockwise rotation) using the atan2 function:
angle_in_radians = atan2(x, y)
Similar, Y and Z can be used to calculate the pitch.
References
- ↑ Tom Pycke, Accelerometer to pitch and roll