DTMF decoding
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Posts: 46,084
Hi all,
I recently put together two transceivers using DTMF tones. The way
I have it set up is I am using a BS2 to transmit and the MT8880CE to
decode the tones. Initially I used a direct connection and I had no
trouble at all. I then took two motorola T5620's and used them for
my transmissions. Everything seems to work ok but the only thing I
can't figure out is that it will not decode the number 3. In
addition, it has trouble with 6 and 9 but it will get them most of
the time. I double checked everything on the board and like I said,
if I use a direct connection it will not work. I would like to know
if someone has used this type of communication and if so what kind
of results have they gotten. If anyone is an expert with DTMF
please shed some light on this.
Thanks,
Chris
I recently put together two transceivers using DTMF tones. The way
I have it set up is I am using a BS2 to transmit and the MT8880CE to
decode the tones. Initially I used a direct connection and I had no
trouble at all. I then took two motorola T5620's and used them for
my transmissions. Everything seems to work ok but the only thing I
can't figure out is that it will not decode the number 3. In
addition, it has trouble with 6 and 9 but it will get them most of
the time. I double checked everything on the board and like I said,
if I use a direct connection it will not work. I would like to know
if someone has used this type of communication and if so what kind
of results have they gotten. If anyone is an expert with DTMF
please shed some light on this.
Thanks,
Chris
Comments
fundamental frequencies of the digit being sent.
I suspect the tones generated by the stamp are getting mixed together in the
T5620's (whatever they are?) producing
more than just two tones which confuses the decoder. Perhaps if you put an
Resistance Capacitance Filter between
the stamp and the T5620's you might get better results. First a resistance
of around 1000 ohms coming out of the
stamp, then a .1 microfarad cap at the end of the resistor tied to ground,
then that node goes to the T5620. Of course
I am assumming the 5620 has an input impedance of at least 600 ohms.
Original Message
From: "christopher41877" <CHRIS@R...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, July 13, 2004 20:20 PM
Subject: [noparse][[/noparse]basicstamps] DTMF decoding
> Hi all,
>
> I recently put together two transceivers using DTMF tones. The way
> I have it set up is I am using a BS2 to transmit and the MT8880CE to
> decode the tones. Initially I used a direct connection and I had no
> trouble at all. I then took two motorola T5620's and used them for
> my transmissions. Everything seems to work ok but the only thing I
> can't figure out is that it will not decode the number 3. In
> addition, it has trouble with 6 and 9 but it will get them most of
> the time. I double checked everything on the board and like I said,
> if I use a direct connection it will not work. I would like to know
> if someone has used this type of communication and if so what kind
> of results have they gotten. If anyone is an expert with DTMF
> please shed some light on this.
>
> Thanks,
>
> Chris
>
>
>
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