I was more or less thinking about using it with a TNC. I just passed my General so I have renewed interest in it.
BTW, I found some old photos of our belated friend and his "toon town" model T. Should I post them? I can't believe I will soon be the same age he was when I first met him... On Sat, Jul 28, 2018, 3:36 PM Kenneth Pettit <[email protected]> wrote: > 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. > > On Sat, Jul 28, 2018, 3:36 PM Kenneth Pettit <[email protected]> wrote: > 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. > >
