Hi,
I’m running PDOA algorithm on our own custom board.
I wonder where is the Macro AVG_TRIM_PER_PPHM which is defined in tag.c line 95 came from ? Labortary? Is there a way that I could measure it?
Thanks,
Regards.
Hi,
I’m running PDOA algorithm on our own custom board.
I wonder where is the Macro AVG_TRIM_PER_PPHM which is defined in tag.c line 95 came from ? Labortary? Is there a way that I could measure it?
Thanks,
Regards.
Hi
For reference, the AVG_TRIM_PER_PPHM value means “the amount of frequency shift in Parts Per Honderd Million for a single unit change of the FS_XTAL crystal trim register”.
This value depends on the hardware, mainly the 38.4MHz crystal and crystal load capacitors.
See example 02f, “RX with crystal trim”, in the DW1000 API examples for more information on how it is used to automatically trim the crystal offset.
You can find this value for your product by:
Note that this value is an average. The actual change of the center frequency based relative to the trim capacitance is not 100% linear. The linearity also depends on the chosen crystal and load capacitance. On our modules we chose the load capacitors to have a trimming range suitable for the entire working temperature range and to have “good enough” linearity.