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PIC used as DTMF decoder

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josi

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hi! is there a way of using the PIC 16F877 as a DTMF decoder? if so, i really hav no clue on how that can be done! can u guyz help me? thanx
 
Apparently it can. Find complete plans for a 16F877 decoder type pic dtmf decoder into Google.
 
Why cant you use a chip like MT8870 with PIC 16F877?

I'm already using the MT8870DE! but i havn't test the circuit yet! i jus wanna know if i can use the PIC to decode the tones! i did a 1st test with the MT8870 with no success! now i'm trying a diffrent configuration.
 
I have done many projects using tone decoders all are successful.

Without a special decoder PIC could do the job but it needs bigger code to work out.If you can write a code then ok.That mneary's search link has one like that.
 
I have done many projects using tone decoders all are successful.

Without a special decoder PIC could do the job but it needs bigger code to work out.If you can write a code then ok.That mneary's search link has one like that.
happy to hear dat u succeded with the MT8870 coz so far i i'm gettin nothing! can u please send me some circuit diagram? all i want is to hook a nokia 3310 to the chip, and control some devices (on-off). if u hav any other suggestion please let me know. thnx
 
For the MT8870 chip from where & how did you give the inputs?

If it receives a valid DTMF tone it will raise the steering bit while giving a binary output of the present input pulse.
 
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i hooked the3310's speaker to the dtmf chip! then i call the 3310 with another mobile, once the 3310 as answered, i press some keys on the calling mobile! that is suppose to giv me some output on the dtmf chip!
 
I have seen the same issue that josi has posted elsewhere, using many variations of the 8870 inputs circuits as listed in the data sheets, even using different variations.

The trouble seems to be that as soon as 5v power is connected to the circuit, the output pins Q1-Q4 all go high, and remain there, even without any input tone coming in, so any LED, or transistor connected relay, or whatever is immediatly turned ON, and held there.

For those who have had success with these DTMF decoders, any suggestions? I have gone over and re-built the circuit on the breadboard numerous times, and tried 5 different CM8870 chips already, so I would find it hard to believe all the chips are bad.

Is there another way to test if the chips are good or bad here?

Here is the datasheet:
https://www.electro-tech-online.com/custompdfs/2008/12/ics8870.pdf

Here is the schematic from the data sheet:
 

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