In the following link, have the application note abaout decoding DTMF with the MSP430Fxxx Ti microcontroller. The code is simple and reusable for other microcontrollers!
Go in w!w!w.ti.com and search in microcontrollers application notes ok?
There is no problems with DTMF decoding on 1-2 MIPS micro. Please look on my app note AN2107 from Cypress Micro (**broken link removed**) and you can easily to port on own CPU in hours. I test this for many weeks, so it works fine
i think Goertzel Algorithm is difficult to calculate in microcontroller ?
but !!! what about zero Crossing
if i make the DTMF signal to pass throgh zero crossing detector and then microcontroller and calculate number of zero crossing with fixed time
can i detect the DTMF signal :?:
The Goertzel is not good for micro without hardware MAC. I recommend to use the digital quadrature signle bit correlator for CPU w/o ADC and digital quadrature correlator for CPU with 8 bit ADC. Try to test Goertzel algorithm under 8kHz sample rate with spech analysis for classic 8051