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I am working with an LSM9DS1 9DOF IMU and was wondering about some of the choices about operating the magnetometer. This is my first time working with an IMU, so I am having some trouble understanding some of the data sheet with it.

One of the registers (in CTRL_REG3_M) says the system operating mode can be continuous conversion, single conversion, or power down mode. I don't know what the difference between continuous and single conversion mode. I believe this has to do with how the ADC operates, but some insight into the significance of this would be great.

Another register (CTRL_REG5_M) has something that seems similar called block data update. Does this mean that in one case, when I read the output it will update the output register, but in the other the output updates continuously, whether being read or not?

My goal is to sample the magnetometer the magnetometer either at its maximum output ODR of 80Hz, or perhaps faster so that my data rate for the magnetic field corresponds to the data acquired from the accelerometer, which I have set 119 Hz. But I was wondering if these two settings above would have any implications for handing this procedure.

Thanks for the help!

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  • \$\begingroup\$ If you explain the design where you intend to use this part, it will give more context to the answers and you will get better help. \$\endgroup\$ Commented May 31, 2016 at 12:50
  • \$\begingroup\$ @SeanHoulihane Thanks for the suggestion, I added some details about what I want to do. \$\endgroup\$
    – Alex K
    Commented May 31, 2016 at 14:06

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It's all in the name:

  • Continuous - the device does conversions repeatedly and automatically at some defined rate.
  • Single - the device only does a conversion when you instruct it to. This means if you want one sample, you simply ask for one. If you want ten samples, you have to ask for a sample ten times.
  • Power Down - the device is powered down. It does no conversions and the power consumption is reduced. This is a low power/sleep state.
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  • \$\begingroup\$ Thanks for the help, I see the basic idea now :) So does this mean that in power down mode, the ADC is off, but the magnetic sensor itself could still be consuming energy? And for the single conversion mode, is there a way to determine the maximum rate that data can be requested? For continuous mode, would it be possible to pull the same data from the output register twice before it updates? \$\endgroup\$
    – Alex K
    Commented May 31, 2016 at 14:12

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