Will it be possible to feed in a reference clock to the ADALM-PLUTO?

I'm interested in whether it would be possible to use the ADALM-PLUTO time-of-arrival localization. This requires a very stable clock. I wonder whether it will be possible to feed in an external reference clock? In the revision-B schematics, it looks like there is no connector or jumper to switch from the built-in 40MHz oscillator to an external clock.

Also, if I do feed the clock from an external source (even if this involves removing the 40MHz oscillator), how difficult will it be to switch from 40MHz to 10Mhz? I see that the AD9363 does support 10MHz clocks, but will it is reasonably easy to configure the firmware for this clock frequency?

Thanks, Sivan Toledo, Tel-Aviv University

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    •  Analog Employees 
    on Mar 11, 2017 3:30 AM

    Sivan:

    Yes - you should be able to lift off the current oscillator, and use an external clock. There is a hole in the PCB specifically for this purpose. All you need to do is lift C123, and put a 1.3V p-p clock into that node.

    Since we have a 1.8V oscillator, we are using C123/C124 as an AC divider to get things down to 1.3V p-p. The internal capacitance of the pin means we don't actually need to stuff C124 to achieve this.

    The Input Frequency Range for the reference clock is from 10 - 80 MHz. That is spec'ed in the datasheet. After that, it should be a simple matter of updating the device tree to tell the Linux driver you are using something different than 40MHz.

    -Robin

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  • 0
    •  Analog Employees 
    on Mar 11, 2017 3:30 AM

    Sivan:

    Yes - you should be able to lift off the current oscillator, and use an external clock. There is a hole in the PCB specifically for this purpose. All you need to do is lift C123, and put a 1.3V p-p clock into that node.

    Since we have a 1.8V oscillator, we are using C123/C124 as an AC divider to get things down to 1.3V p-p. The internal capacitance of the pin means we don't actually need to stuff C124 to achieve this.

    The Input Frequency Range for the reference clock is from 10 - 80 MHz. That is spec'ed in the datasheet. After that, it should be a simple matter of updating the device tree to tell the Linux driver you are using something different than 40MHz.

    -Robin

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