Hi Drasko, On 7/7/10, Drasko DRASKOVIC <[email protected]> wrote: > On Thu, Jul 8, 2010 at 12:02 AM, Sébastien Lorquet <[email protected]> > wrote: >> Totally agree. Looks like your atmel is OK provided you just add a 3.57 >> crystal clock. You can still make a bitbanged uart if you wish, and use an >> irq as a timer. > > I agree also on this. Moreover, Atmel is already used in similar project : > http://www.adafruit.com/index.php?main_page=product_info&products_id=101 > http://www.ladyada.net/make/simreader/index.html >
Yes I've seen it, though it does it by software mostly, will try to catch what's going on with the hardware, haven't look at it in deep yet, but sure it will, thanks. > So, maybe this project pages will give Luisa some hints... > > Btw, can not the internal Atmel uC clock be divided somehow and let > out via some GPIO or other pin ? Why need for external crystal ? I do > not know much, just asking... > Yes, that's exactly what I tried today. One can output a signal on certain pins by hardware, without it generatig a software interrupt, but I didn't have any success yet, same results. I think the problem lies on the output signal and the interrupt (the one which samples the i/o line not being in synch). Hence why the need for a clock, one setups usart and recieves just what the card sends (the transciever does handle start and stop bits, etc). Not sure yet how to synch with the external clock with usart either, but I'm pretty sure that by going the usart way, the stop bits needed when one wants the card to repeat las byte are not going to be easily accessible, but we'll see. > >> As a side note, to sample the IO line, ISO7816 requires to read the line >> at >> the middle of the bit. You're not required to average more than one read. >> Just have your irq run a twice the bitrate so that you can read the bit in >> the middle, and toggle the IO line at the right moment for sending. > > I agree also on this - sampling one value on I/O line in the middle of > the ETU should be quite sufficient. > > Luisa, > good luck and keep us informed on your interesting project. Thanks, will! > > BR, > Drasko > > _______________________________________________ > Muscle mailing list > [email protected] > http://lists.drizzle.com/mailman/listinfo/muscle > _______________________________________________ Muscle mailing list [email protected] http://lists.drizzle.com/mailman/listinfo/muscle
