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ADIS16475 Direct Sync Mode and Pulse Sync Mode

In the description of Direct Sync Mode and Pulse Sync Mode on pages 26 and 27 of the ADIS16475 datasheet, the text only refers to "accelerometer samples"; the gyro is not mentioned. My question is: when does the gyro data acquisition take place? Can this also be set using an external clock? Will it occur at the same time as for the accelerometer?

Could you also clarify the sentence "Using pulse sync mode also lowers the bandwidth on the inertial sensors to 370Hz."? Is this because the maximum accelerometer sampling rate in pulse sync is equal to the output data rate (at most 2 kHz), while the maximum sampling rate in Direct Sync is twice the output data rate (so sampling at 4 kHz for the maximum output rate at 2 kHz), since the samples are averaged?

PS. Are there any libraries available for the ADIS16475?



added PS
[edited by: Mr.T at 12:05 AM (GMT -5) on 21 Nov 2018]
  • Hi Mr.T

    Did you get any feedback on this post that you can share?

    I'm having the exact same question...

    Thx

  • Hello Mr. T! 

    I am very sorry about missing this!  We are in the process of expanding our team, which is going to help address this gap, but in the short term, we are stretched pretty thin right now. I have some information, which will help.  I will answer each question in separate answers....

    NevadaMark

  • QUESTION: 

    In the description of Direct Sync Mode and Pulse Sync Mode on pages 26 and 27 of the ADIS16475 datasheet, the text only refers to "accelerometer samples"; the gyro is not mentioned. My question is: when does the gyro data acquisition take place? Can this also be set using an external clock? Will it occur at the same time as for the accelerometer?

    ANSWER: 

    Direct control of gyroscope sampling is not possible with this product.  Sorry about that. 

  • Dear Mr. T,

    The ADIS1647x family read the gyros at approximately 2 kHz asynchronous to the actual gyro output update rate of about 4 kHz.

    The external sync replaces the 2 kHz clock internal to the IMU and that clock only influences when the gyros are read. Since the clocks are independent, the gyro update and the external/internal clocks walk relative to each other. As a result, the reading of the gyroscope's samples can be offset anywhere from 0 to ~250us from the gyro's internal data sampling clock.

    The timestamp is only used in the PPS external sync mode, and would not be useful in the regular external sync mode.

    -Paul Kern