Beware: the line is *toggled* every 10 clock pulses, so a period is 20 pulses or 1 MHz :)
On Fri, Jul 9, 2010 at 3:54 PM, Drasko DRASKOVIC <[email protected] > wrote: > On Fri, Jul 9, 2010 at 3:42 PM, Luisa <[email protected]> wrote: > > Hi Sebastien, > > > > It seems I have to wait for a week or so till the crystal arrives. > > Though I'm also sure one can get advantage on the hardware usart to > > get things done and it's the way to go. > > > > However, been testing this "by hand" now that I had some spare time at > > 1Mhz, with no success so far (I've got the impression I won't have it > > either when the crystal arrives and I setup the hardware accordingly, > > because of the problem here being some other that I can't see). > > > > What I'm doing now, with a 20Mhz clock on the chip, instead of the > > original 18Mhz one: > > > > * I setup the card's clock line to toggle each 10 cycles, hence giving > > me a full-swing 1Mhz signal on the output pin, though I don't yet let > > it toggle. > > 20Mhz / 10 = 2Mhz, not 1Mhz. Though the cart should work fine for all > frequencies between 1Mhz and 5Mhz, > I suggest you to use 1Mhz for the beginnig. > > > > > * I activate the contacts appropiately, including the card's clock line. > > > > * Just after I activate the contacts, no interrupts or whatsoever, I > > just fall into a loop where I sample 80 bits on the i/o line each +/- > > 372 uS (have also tried with more and less, though this time the card > > actually sends bytes as expected, each +/- 372uS). > > If you are clocking your card with 2Mhz, you should not sample at 372uS. > Again, the formule is : initial ETU = 372 / Fcard_clock. > > For 1Mhz, initital ETU = 372 uS. > For 2Mhz, initial ETu = 372 / 2 = 186 uS. > > BR, > Drasko > _______________________________________________ > Muscle mailing list > [email protected] > http://lists.drizzle.com/mailman/listinfo/muscle >
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