Connecting MT8880 DTMF transceiver

[planet69]

I'm using MT8880 to generate DTMF tones only.
My question is how should I terminate the IN+, IN-, GS, Vref, Est, St pins which I won't be utilizing.

Thank you

 

[matthai]

my fully working circuit may help you


View attachment KEYLESS ENTRY.pdf


actually this is dtmf tone decoder, i don't know how to generate tone from this

 

[tpetar]

Alarm Dialer

http://www.elektronika.ba/505/phone-call-alert/


You can replace 8880 and 8870 with µC, both PIC and AVR can make DTMF using PWM, and of course to decode touch tones. Even ATTiny and PIC12F series of µC can do the job. 8880 is unduly expensive IC for that job, and 8870 is obsolete, maybe both.

MT8880 datasheet
**broken link removed**


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my fully working circuit may help you


View attachment 82655

You show us 8870 IC its decoder, he need DTMF (touch tone) encoder 8880. DTMF cannot be generated by 8870 decoder.

 

[planet69]

Appreciate it, guys but i do know how to use the MT8880C.
It's just this one case which i'll be using only the dtmf generator function of the MT8880C. The control pins are permanently set to write mode. It seems that leaving those pins opened does not give any adverse effect on the chip itself and the dtmf generation seems to work ok.
I fear it is unwise to leave the 'unrelated pins' 'opened'. How shall i terminate them if otherwise.