Marko Mäkelä wrote: > Therefore, we can use 8 samples for data and 1 or 2 samples for "stop > bits", to allow for storing the byte and for resynchronization. The raw > speed would still be 4410 or even 4900 bytes per second, although I think > that the latter (doing only with one stop bit) would require scattering > the pointer incrementation and comparison operations in the unrolled > byte-receive loop, which is a somewhat non-trivial task. Had these > conferences I'm participating in been more boring, I'd probably already > have such a routine. :-) Using one stop bit could cause problems when there's a (long) series of $FF-data. CD-players (like every audio device) have a high-pass filter as well. > A word on the hardware. I think it could be done with 3 or 2 ICs. One > amplifier-limiter (for converting the line-level signal, 1 volt > peak-to-peak or something like that, to TTL, maybe with some sort of a > Schmitt trigger), There are default voltage comperators for that. Operate on 0 and 5v. > and something to convert the rising and falling edges of > the signal to pulses between 1 and 21 microseconds (those are the limits > for the pulse width; the actual width should be constant). There's a (dirty) possible solution here: Attach a resistor and a small capacitor from GND to the output of said comperator. (capacitor towards GND). Another voltage comperator could compare the voltage at the junction between R and C to (for example) 0.69 * VCC, which results in a delayed version of the original signal. One XOR on original and delayed signal will do the trick. There's one problem though: noise. Schmitt-triggers would be quite a lot better, but it might be a problem to have them trigger on the 1 Vpp signal. -- Martijn van Buul - Pino@dohd.cx - http://www.stack.nl/~martijnb/ Visit OuterSpace: mud.stack.nl 3333 finger firstname.lastname@example.org for my public key block - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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