I'm considering preordering a Goliath expansion board but I have a few
questions regarding parts of its functionality.
1) The battery charger: does this charge one set of batteries by drawing
power from another source of batteries, or does it source its power
2) 3-d accelerometer: in what form is the accelerometer information
obtained? Is it obtained as three X, Y, Z numeric values which are
constantly updated? Is it possible to derive information about speed
from the accelerometer output? Possibly through integration techniques?
I know this is a relatively new piece of hardware, so any speculative
opinions would be most welcome.
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On Jul 22, 2007, at 10:14 PM, Ali, Imran wrote:
> 1) The battery charger: does this charge one set of batteries by
> power from another source of batteries, or does it source its power
The battery charger is powered from the power socket.
> 2) 3-d accelerometer: in what form is the accelerometer information
> obtained? Is it obtained as three X, Y, Z numeric values which are
> constantly updated? Is it possible to derive information about speed
> from the accelerometer output? Possibly through integration
The part is LIS3LV02DQ -- datasheet is here: <http://www.st.com/
The part indicates when it has a new data sample, which can be
programmed to happen at between 40Hz and 2560Hz. You can then read
the data value(s) from it via I2C -- I wouldn't be surprised if an
I2C chip driver for the thing were written pretty quickly, which
would provide a more convenient userspace interface. You should be
able to approximate distance by integration, but you'll drift over
time from true position unless you correct. But over short
distances, and combined with the GPS option on the board, you should
be able to get very nice relative position estimates.
> I know this is a relatively new piece of hardware, so any speculative
> opinions would be most welcome.
The accelerometer was wired wrong on the most recent prototype I had
(tied to the gumstix I2C bus, but forced into SPI mode rather than
I2C mode due to misreading of the datasheet, so I couldn't actually
talk to the chip. But it looks like it should be pretty neat.