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Forum Index : Microcontroller and PC projects : Decoding DTMF
| Author | Message | ||||
OA47 Guru  Joined: 11/04/2012 Location: AustraliaPosts: 911 |
I thought I might throw this one onto the think tank. Has anyone any ideas on how to decode DTMF in basic with a 'mite? |
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kiiid Guru Joined: 11/05/2013 Location: United KingdomPosts: 671 |
I don't think it is going to be an easy job using the 'mite only... Try by connecting MT8870D to it. http://rittle.org -------------- |
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| Gordz Regular Member  Joined: 10/08/2013 Location: AustraliaPosts: 55 |
Its pretty tricky because is is two frequencies at once. MT8870 is the way to go for sure |
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| phiber Newbie  Joined: 19/09/2013 Location: United StatesPosts: 8 |
This is not as hard as it first seems in software. While it's obviously really easy to add an MT8870 to your circuit, if you'd rather do without an extra chip, the PIC32 has more than enough processing power to do DTMF detection in software. The textbook algorithm most commonly used in telephony for DTMF and MF detection is the Goertzel algorithm, which is a type of digital filter. You can read about the math behind it in wikipedia. There is a REALLY good example of Goertzel purely in software, used in the Asterisk software PBX. You can peruse the DSP code here. I chose the older Asterisk 1.0 since the codebase was simpler back then. Regards, Mark |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3678 |
Some explanation etc hereDTMF John |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 5923 |
That is a very good explanation and worth some experimenting. Jim VK7JH MMedit MMBasic Help |
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