dtmfout problem

[lerameur]

I think I might got the probe switch to 10x instead of 1x.. that would explain the 40v. I will check it once I get home...
if so I guess I would have would have something like 3.7v output peaks on the pin.

[lerameur]

Ok , the scoipe was set at 100x. now I read 4v at the output, but still a lot of noise after the filter, and only dials 50% of the times

k

[skimask]

but still a lot of noise after the filter, and only dials 50% of the times
k

Well, the PBP manual does say that any 'sound' output from the PIC, being 1-bit analog, is going to be 'noisy', a lot of harmonic content. And I would think that even if it's filtered well, it would still have a load of 'noise' in it. A low-pass 'brick wall' filter, with a steep 'slope/cutoff', with the -3db point set just above your highest frequency might handle that.
I guess I'm not really sure. I haven't relied on the PIC to do much sound (other than moving MP3 data back and forth for a player).

[lerameur]

I was initially thinking of going with a specialized DTMF chip. They are hard to get around here

[skimask]

I was initially thinking of going with a specialized DTMF chip. They are hard to get around here

I wouldn't think you'd need a special chip...just maybe brush up on some filter design techniques. After all, what you're trying to do has been done probably hundreds of times before. No reason why you can't do the same thing...

And also...

Here == ???????????????

[Darrel Taylor]

I'm not sure what affect it will have on DTMFOUT, but you have ....

ANSEL = 1

Which puts PORTA.0 in Analog mode.
And that's the DTMF pin.

Might try ...

ANSEL = 0
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[lerameur]

that did not work,
everytime a DTMF comes out, its like someone was blowing air at the same time.. from what I can hear from the speaker.
if I choose to do a low pass filter, what would you suggest my cut off frequency be?