In SX Microcontrollers, SX/B Compiler and SX-Key Tool, johncouture wrote:

If I may humbly suggest that the SX is not well suited to that type of activity.  DTMF means that you have to produce two PRECISE tones at the same time.  The SX can do it but you would burn far fewer brain cells by using something like a DTMF transciever and having the SX control it  That way the SX is doing the heavy lifting of calculations, monitoring inputs, sending status messages, etc.

Take a look at the datasheets for:

MT8889C - Integrated DTMF Transciever (about $5?)
TCM5089N - Touchtone Generator (Jameco 32803, $5)
LM567 - Tone Decoder ($1) Althought you can wire several of these together to interpret DTMF signals, this is probably more useful for detecting a single tone.
CM8880 - PDIP20 DTMF Transciever
CD22202 - DTMF decoder
TelTone 8870 - http://www.boondog.com/tutorials/dtmf/dtmf.htm#Parts


Just a suggestion.

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