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I am working on a project where I want to get very accurate data from an accelerometer. I plan on sending my data over bluetooth to be interpreted by a computer.

I am assuming that bluetooth will have some unknown delays that come from things such as how Windows handles the data.

So, since the accelerometer data is time depended, would I be benefited by using a clock that can easily create time in some even divisor of seconds? Or possibly add a RTC? I would then be able to "time-stamp" my data before sending it over bluetooth.

Is this worth it or am I just over thinking how accurate I can actually get my data to be?

Clarification:

I will be pulling in data based off of a timer interrupt. I am wondering if my timer needs to be something like 0.5ms. I would go ahead and "time-stamp" the messages I am sending so I know if I loose a message for some reason.

Also, I am using a digital accelerometer, so I am not doing an ADC, instead I am getting the measurements over I2C.

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  • \$\begingroup\$ With bad time between messages it will mess up your filtering. Jitter is the end of all excellently designed digital filters. \$\endgroup\$ – Kortuk Dec 19 '10 at 18:46
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It sounds like your measurements are already on an even interval controlled by your device, so you could simply add a serial number to each measurement or block of measurements to ensure that you don't lose one. This could be as simple as a single byte, which would have lower overhead than a full time stamp.

While a dedicated RTC could provide very accurate time stamps, it would not necessarily make the timing of your measurements any more accurate unless you drive those samples off an interrupt from the RTC. What matters from a filtering standpoint is how low the jitter is on the sampling of the signal, not on receiving the data.

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  • \$\begingroup\$ Thanks! For some reason I wasn't thinking about this in the right mindset. \$\endgroup\$ – Kellenjb Dec 19 '10 at 21:34

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