piclist 1999\10\27\172524a >
Thread: HT9200A problem (DTMF)
www.piclist.com/techref/pots/dtmf.htm?key=dtmf
picon face BY : Lea email (remove spam text)



       Hi all, I'm in trouble with a DTMF encoder that I'm trying to use
in a new proyect, the HT9200A from HOLTEK, it's a serial (2 wire) DTMF
encoder very easy to use, only 3 wires needed (CE , SDATA, SCLK), the
logic is working fine and the tone is generated but at the begining and
the end of each tone I heard a very short sound "TAC" , in the scope
I can see that I have a DC jump at the begining and at the end of the tone
and I have no idea how to avoid that DC jump!.
using coupling capacitors I found no difference, the ugly sound persist :(
the only way that I could avoid that sound is change the tone without
stop it, but most dtmf decoders needs at least 30 ms of silence to detect
a new tone, so I think that is not the solution.
anyone have an idea about how to avoid this DC jump sound?.
thanks in advance.
  Leandro J. Laporta (LU2AOQ)
  mail: lu2aoq@spam@spamKILLspamyahoo.com
  wrk: Arg. Assoc. for Space Technology.
  ham: TCP/IP high speed group HSG

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Subject (change) HT9200A problem (DTMF)

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