DTMF Detector Using Holtek HT9170B/HT9170D DTMF Detector

Using a Using Holtek HT9170B/HT9170D DTMF Detector

 ;**************************************************************************
 ; dtmf001.asm
 ;
 ; PROGRAM:    Simple Parrallel to Serial to take output from 
 ;			Holtek HT9170B/HT9170D DTMF detector
 ;
 ; AUTHOR:		Doug Rice, 
 ;			doug.h.rice@btinternet.com

http://www.dougrice.plus.com/dev/dtmfCode/

DataSheet: http://www.dougrice.plus.com/dev/dtmfCode/HT9170v120.pdf

PIC Assembler code: http://www.dougrice.plus.com/dev/dtmfCode/dtmf001.asm

The Holtek chip has an analogue input and outputs.

 DV - Goes high when DIGIT is detected, and low when DTMF ends.
 D0 to D3 - outputs DTMF digit code  

In 2004 , I tried to use a PIC chip to take the outputs from the DTMF detector and output the digits detected.

I was using PIC chips with 4Mhz, and could not work out how to decode DTMF using the AtoD.

Recently I have recorded the audio using Audacity and decoded the audio samples using a web page.

https://www.dougrice.co.uk/cgi-bin/wiki.pl?WebAudio

http://www.dougrice.plus.com/dev/UART/UART2_DTMF.htm - The webpage decodes the Audio and uses the CANVAS to plot the decode

This demo simulated DTMF detection, and used SVG graphics to plot the output of the simulation:

http://www.dougrice.plus.com/dev/dtmfCode/dtmf1_g.svg

It should be possible to use Web Audio now.

https://homepages.plus.net/dougrice./dev/UART/micBaudotDecode.html - decodes BAUDOT, so converting to DTMF should be a few evenings work.

Sampled Audio:-

State Machine: - Spec

State Machine: - As the Testers and Windows present it