accelerometer driver

Andy Green andy at
Fri Aug 29 08:05:39 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| Harald,
| I have heard a lot of mysteries around the accelerometers.
| Are they very sensitive or not? How sensitive? Are they calibrated
| somewhere?

They are calibrated at factory, there is EEPROM in them IIRC that is
loaded at powerup containing the device-specific calibration coefficients.

| In the factory we saw big variations of values they produced, when lying
| flat on a table. Nobody could really understand why.
| Do we need 2 accelerometers, if they are already 3D? We are planning to
| take one out in future products... What do you think?
| Until today there are bugs in the driver talking to both at the same
| time I think, in other words even if there is some advantage to having
| two, they are not working right yet...

I don't know anything about advantage of having two, but I think talking
~ to them on shared bus is working OK now, at least it is here, something
else affects communication.

Analogue ones are not that great anyway as I said we have to run them
all the time instead of using the threshold quench stuff.  As Harald
said noise from routing would definitely make trouble on analogue
version of LIS302 (ALB), it has 32K output impedence already, so they
would have to be buffered with opamp at the device before the long
routing.  But with that and considering unusually low bandwidth on them
so a capacitor at the ADC input to filter them too is possible, it would
be OK I think.

But agreed there's no point, the smart ones with integrated ADC should
be better.

- -Andy
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