DTMF and other telecom signalling using PIC16F

This work was undertaken between 1998 and 2003. I have reproduced this work here to create a more permanent online record. Whilst microcontrollers have progressed immeasurably since the PIC16F, the tone generation techniques and line interface circuits still remain valid.

In 1998 a PIC16 series microcontroller was available for just under $0.50, whilst DTMF encoder and decoder ICs were about $2 each. Creating reliable, industry standard DTMF tones in firmware would result in a huge cost saving.

I present a tutorial in Word format which documents the techniques involved. PIC16F sourcecode is included.

A series of hardware and firmware techniques to generate high purity DTMF signalling tones using a PIC16Fxx microcontroller.

Extended to include V23 modem tone generation and decoding to allow Caller ID reception on PIC16Fxx, with the objective of low baud rate bidirectional communication between microcontrollers across a standard telephone line.