Hi Rob,
connecting two PICs is not like an audio recording. Better connect the pic to
your soundcard to record and then playback, that way you'll get something
similar to a tape recorder.
The difficulties when using audio equipment are (at least):
- only alternating current is transmitted- the volume is never exactly the
same- the frequency range is limited to like 100Hz-10kHz- the line level
voltage is less than 1V
Reading should be possible by most PICs which have comparators. Only a
resistor is needed, then you can detect zero crossings.
The Sinclair ZX81 used audio equipment as storage. A burst of three
oscillations coded a zero, five coded a one. The output was low-pass filtered.
You usually had to try loading a program several times, slightly adjusting the
volume, until you got lucky.
Greets,Kiste
Am Donnerstag, 24. Februar 2022, 19:56:01 MEZ hat Rob CJ
<[email protected]> Folgendes geschrieben:
Hi Hans,
If I understand you right the only thing you want to do is to record a signal
or a sequence of signals on a casette player that can be used to trigger
something when the recording is played back right?
If my initial suggestion would work - which may work since I have the idea that
my Apple II did more ore less the same thing - I could give it a try to do a
proof of concept.
I may have a the problem that I do not have a casette recorder but I could fake
it by just connecting two PICs to see if that works. The final test could then
be done by you.
Which PIC type are you using?
Kind regards,
Rob
Van: [email protected] <[email protected]> namens hans
<[email protected]>
Verzonden: donderdag 24 februari 2022 17:07
Aan: jallib <[email protected]>
Onderwerp: Re: [jallib] PWM serial audio transmission Another piece of text:
So far I've done everything with MIDI. I used one midi channel for the actions
with a general command type. Then 2 data, one for the device nr (16) and one
for the command. (0-128)
This has worked well for years, but it does require a complete MIDI sound
package.
Op donderdag 24 februari 2022 om 16:55:46 UTC+1 schreef hans:
Hey ,
I have tried a circuit with an MT8880 but the ICI has failed. I did hear the 16
tones, but when I wanted to receive them, the chip gave up the ghost.
In theory I understand your suggestions well, but developing something like
this is not easy for me. I'm just a LEGO builder.regardsHans
Op woensdag 23 februari 2022 om 19:30:37 UTC+1 [email protected]:
Hi Hans, Kiste,
You can still by DTMF decoders and I assume also DTMF encoders. Just look at
for example Aliexpress and type DTMF.
But another suggestion. Many, many years ago I had built an Apple II and I
used cassette tapes to store and load games which was using tones generated by
the Apple II itself using two tones, one for high, one for low and one as a
lead-in tone (not sure in the lead-in tone was another tone) to synchronze the
start of the recorded program. You would not need this lead-in tone in your case
So I think it may not be that complex:-) For recording on casette, generate
this dual tone by the PIC via PWM or maybe it is also sufficient to generate
one tone in case of a 1 and no tone in case of a 0 but I think this will be
less reliable.-) For playback, measure the length of the recorded PWM tone. If
is is within a certain range you accept it as a one and in case of two tones
the lower tone could be zero and the higher tone is one.
As long as the tone frequency is not too high, I think this could work.
A more advanced solution would be to use a phase locked loop (PLL) but I am not
sure if it will work. The PLL locks to the input signal so the voltage that
controls the oscillator goes up and down to follow (lock on to) the input
signal and this oscillator voltage signal could then be used by a comparator of
the PIC to detect a high or low tone. You can also use the oscillator of the IC
to generate the two tones by controlling the oscillator voltage by the PIC. A
typical IC for that is the HEF4046. I have used this IC many many years ago
too. This solution may be bit over the top since you only want a kind of
trigger signal
But maybe the first solution is more doable. Just give it a try.
Kind regards,
Rob
Van: 'Oliver Seitz' via jallib <[email protected]>
Verzonden: woensdag 23 februari 2022 09:58
Aan: [email protected] <[email protected]>
Onderwerp: Re: [jallib] PWM serial audio transmission Hi Hans,
20 years ago I would have suggested using DTMF, but the decoder chips are rare
these days...
PIC controllers include various peripherals which can be used to encode and
decode DC-free signals (which, apart from the frequency below, say, 10kHz, is
the requirement to be recorded as audio). On/off keying or frequency shift
keying are the easiest, I think. Which chips are you going to use?
Greets,Kiste
Am Mittwoch, 23. Februar 2022, 09:15:43 MEZ hat hans <[email protected]>
Folgendes geschrieben:
Hello everyone,
I have been trying for a long time to place a serial signal on one track of an
audio recording which I can read afterwards. To make all kinds of things happen
at the same time as the audio is played. I have now tried to do this with the
old modem system ( TCM3105) but it failed hopelessly. I read that there are
also systems to do this using PWM. Does anyone have an idea?
regardsHans
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