DTMF decoder HT9170D is not detecting tones properly

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shivakumar.r

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Dear friends,

In my project i use SIM900A gsm module and HT9170D dtmf decoder and Atmega64a controller.
DTMF decoder is not detecting the tones properly....some times it works and some times it does not work.
I use the same application circuit as given in datasheet page number 8,application circuit 2 .
Please help me.....
 

can any one give me the component values of DTMF decoder HT9170D for vdd of 3.2v....
 

recommended that you use a 5V VDD and if DTMF input from the speaker SIM900, you are advised to use difrential input circuit and capacitor values ​​between VDD and RT / GT changed to 85nF (to avoid detection sometimes)


I have experienced what you have experienced, the way to success


goodluck
 

Thanks for the feedback....
I will try this and update as soon as possible...
My controller (ATMEGA64A) is powered up by 3.2v supply.., as per your suggestion if i power up the DTMF decoder from 5v,then DTMF outputs D0 to D3 and DV signals will be 5v.
Can i give this 5V signal directly to the I/O of controller which is powered by 3.2V??..Will it not damage the controller I/O pins???...Or is there any a way to reduce this 5v to 3.2v??
please provide the circuit...
Also can any one give the C code for reading the DTMF tones...I suspect i might have made some mistake in software...
 
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actually uses 3.2V VDD can, because HT9170 uses power supply 2.5V- 5.5V,it is intended to adjust the VDD3.2V uController atmega

see the datasheet below

see page 7 (figure 2 (b)) and 9 (figure 5 (b))

*figure 2(b)
C= 10uF (nonpolar)
R1,R2= 56k
R3=68k R4=47k R5=150k

*figure 5(b)
C=68nF
R1=330k R2=100k D1=1N 4148
 

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