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Configuring AD9361 for use with reference oscillator instead of crystal

Question asked by njp on Jun 20, 2014
Latest reply on Jun 24, 2014 by tlili



We've recently made our own board using the AD9361,  Previously, we were working with the FMCOMMS2 and Zedboard.  On our custom board, we use a 40MHz reference oscillator connected to pin XTAL_N (M12) and XTAL_P (M11) is left open per the AD9361 datasheet.


When porting our Zedboard software/firmware to our board, I forgot to set "adi,xo-disable-use-ext-refclk-enable" in the devicetree (as it was commented out for the Zedboard DTS).  Thing is, even without xo-disable-use-ext-refclk-enable set, I could still configure the RFIC from Linux and get IQ data from the chip.


I rebuilt the devicetree with xo-disable-use-ext-refclk-enable set, and I'm actually seeing no difference in the behavior of the AD9361 (i.e. IQ looks the same).


So, what is "xo-disable-use-ext-refclk-enable" doing?  The reason I ask is that we're seeing some spurs of the 40MHz clock and we're trying to hunt it down.  The spurs of course could be a result of many things, but I'd still think xo-disable-use-ext-refclk-enable should have some effect on the IQ data we collect.




Edit: I should add that I'm using the AD Linux kernel from around the beginning of May.  It's still Linux 3.13.