[sebhc] H8-5

[William Elkins]

Carroll

This is a guess!

On the H8-5 card the clock for the serial uart and the 4800hz clock
for the modulator were from the same source. Sounds like the PC serial
port is not in phase with your 4800hz clock. As a test, I think you
can change the data rate to 300 baud on the H8-5 and you PC and it
would be more likely to work.

Bill Elkins

> But what I want to do is to connect the serial port on my PC to an FSK
> modulator to create the 1200 Hz and 2400 Hz audio tones that can be fed into
> the H8-5 tape input jack. The device should convert the serial data to audio
> tones for the H8-5 and they should be identical to the tones  from an actual
> tape.
> I built up an FSK modulator that is just like the one on the H8-5 board. I
> feed a 4800 Hz square wave to 2 J-K flip flops (74LS131 I think). At any
> rate I am using the same circuit that Heath put on the H8-5 card. I am
> watching the audio on my scope, and it looks identical to the wave shown on
> the Heath waveform drawings.
>
> Only 1 time in my trials did it even start to load. The rest of the time it
> does nothing.

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