Hi all, The cassette input HW/SW "measures" the pulse width of the HIGH period of a square wave generated from the input sine wave. A count > 21 is '1' while a count < 21 is a '0' (or is it the other way around...don't have the book in front of me).
So if a count value can be found to discriminate between 1200 and 2200Hz, then it *might* be possible. The question then becomes an issue with keeping up with the 1200 baud rate. Ken Sent from my iPhone > On Jul 28, 2018, at 11:53 AM, John R. Hogerhuis <[email protected]> wrote: > > > >> On Sat, Jul 28, 2018 at 10:14 AM, Douglas Quagliana <[email protected]> >> wrote: >> I'd like to know if there's a way to get the cassette port to recognize >> AX.25 Bell 202 packet radio tones (1200 Hertz and 2200 Hertz at 1200 baud). >> I think the cassette port audio input pin get routed to the CPU but it only >> knows "HI" and "LO" so I don't think it can detect sinewave waveforms, but I >> would really like to be proven wrong on this. If it worked, it would let you >> run packet radio right off the cassette port and use the cassette motor as >> a push-to-talk. >> > > The cassette protocol is based on measuring time between zero crossings. My > understanding agrees with yours that unlike, say, the Coco, the cassette > hardware cannot be used for general A/D conversion. > > -- John.
