andy pugh wrote: > On 15 July 2012 14:45, Gene Heskett <ghesk...@wdtv.com> wrote: > > >> But the internal calculations for velocity etc are done at the servo >> threads granularity of nominally 1 millisecond. So there is no chance of >> the figures being accurate when the count may be up to a millisecond old. >> > > The counts shouldn't be more than a thread-dither old (10uS or so). > The calculation function reads the latest count from the base thread > functions (possibly a base-thread old). > > The FPGA in the Pico card being discussed here ought to make an even > better job at being up-to-date. > The Pico Systems USC does not have this feature (timestamping of encoder count arrival). The UPC does. The position CAN be thought of as "stale" as the encoder gives no info between counts. So, if it crossed the boundary to a new position a while ago, you have no way to know how close it is to crossing the next boundary.
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