DTMF receiver probs

[toxicmouse]

Michael Jeffery did that nice work on the picaxe DTMF generator in November, which seems to work nicely but i can't seem to get the DTMF receiver to decode the tones.

i am using the HT9170 DTMF receiver with a 14M, using Michael's DTMF generator as the input signal. i have used a condenser microphone and piezo sounder, and also just connected the DTMF output to DTMF receiver input (and common ground)- both without success. curently i am only checking the DV output (data valid) for any responses. i might need to tweek something but i am not too sure what. any suggestions would be greatly appreciated, thanks in advance.


datasheet for the receiver:
http://www.rapidonline.com/netalogue/specs/82-4078e.pdf


michael's thread:
http://www.picaxeforum.co.uk/showthread.php?t=8140&highlight=dtmf

 

[inglewoodpete]

There are 3 points to look at:
1. Frequencies. Are the tones within the 1.5% required for DTMF. A DVM with frequency measuring capability will help here.
2. Wave shape. Is the input to the HT9170 close to a sine wave? The ouput from the PICAXE is harmonic-rich square wave and requires filtering.
3. Levels. Is the input level to the HT9170 in the correct range of levels?