I was planning on using an L3G4200D gyroscope in a project to align manufacturing rollers. I've been looking at the datasheet and it says that the clock rate is 10 MHz but it also has something about a "Output Data Rate" and it can be set to 100, 200, 400, and 800 Hz. That's way lower than the supposed clock rate so I was hoping someone could clear this up. I also don't understand what they mean when they say "Cut-Off" along with the ODR.

This is the product page, it has a link to download the datasheet (PDF) http://www.st.com/web/en/catalog/sense_power/FM89/SC1288/PF250373

The ODR is on page 29. The clock rate info is on page 12.

Note: We are using the SPI interface. (Almost forgot to mention that).

  • \$\begingroup\$ You are aware that is this a rate gyro and not a gyro? i.e. it gives the angular velocity not the absolute rotational position that I assume a roller alignment system might need. \$\endgroup\$ – placeholder Oct 9 '13 at 2:45

The "Output Data Rate" is not the bit rate of the interface, but rather the rate at which it samples the values being measured. If you set the Output Data Rate to 800 Hz, you will read out a packet of data every 1.25 ms using a SPI data rate of 10 MHz.

The cutoff frequency for the low-pass (antialias) filter associated with the sampling process is tied to the Output Data Rate.


10 MHz refers to the max SPI clock rate you can use, not the rate of any on board clock.


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