On Fri, 27 May 2005, Dave Tweed wrote: > Wouter van Ooijen wrote: >>>> 2 You think strobing a 7-seg is time critical? >>> >>> Indeed. You think it is not? >> >> Indeed. There are somne timing-related aspects that might matter, but it >> does not matter whether the refreshing is done at 200 Hz or 10 kHz. > > No, the specific refresh rate doesn't matter (much), but the duty cycle > has to be dead on. And the refresh rate must be stable, because any > changes in frequency cause momentary changes in duty cycle as well. Do you think that the user will be able to see a 3% light output change, caused by a 3% duty cycle variation ? With 1 usec Tcyc and 200 Hz refresh 3% will be 3% of 1250 Tcyc, or 37 cycles. That is enough leeway that most times one need not write isochronous code. Peter -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist