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danielkr
Joined: 27 Aug 2006
Posts: 5
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| Acoustic data transmission with PIC |
 Posted: Tue Aug 29, 2006 1:51 pm |
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Hi folks.
My plan is to implement a data transmission between two PICS with basically speakers and microphones. Have anyone seen anything a project like this before?
After some reading and googling I think I will use an AM-modulation or a modulation built by sending two diffrent frequencies, one meaning 1 and the other meaning 0.
I'm planning to do the A/D sampling and generation of output signal from one single PIC, what do you think of the demands on this PIC. no. timers etc?
To be updated... 
Cheers!  |
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Ttelmah
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| Posted: Tue Aug 29, 2006 2:29 pm |
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Add an NE567, and make your job easy. To do tone decoding on a PIC with no other hardware, will be a major job, and unlikely to be reliable, even if you can get it to work...
Best Wishes |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Re: Acoustic data transmission with PIC |
| Posted: Tue Aug 29, 2006 2:35 pm |
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| danielkr wrote: | | Have anyone seen anything a project like this before? |
There is a number of designs out there for PIC-based ultrasonic rangefinders. From a hardware perspective, an ultrasonic rangefinder is similar to a communication system. A typical rangefinder consists of a transmitter and a receiver connected to the same PIC. If you take 2 pieces of such rangefinder hardware, you can write firmware that would make them communicate to each-other. |
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Ttelmah
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| Posted: Tue Aug 29, 2006 3:00 pm |
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The rangefinders all use either an external filter, or rely on the filter behaviour of the resonant transducer, to detect the tone. Effectively, they only have to time digital data. A huge difference, and a lot more easy than trying to decode a tone in software. I designed one of the smallest of these units on the market, and did the whle thing in an 8pin PIC. Trying to actually decode a tone, is a couple of orders of magnitude harder, and to do it reasonably 'well', is another order of magnitude beyond this....
Best Wishes |
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Storic
Joined: 03 Dec 2005
Posts: 182
Location: Australia SA
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| Posted: Tue Aug 29, 2006 3:25 pm |
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sound simular to a project I have started however not finished as yet, (waiting for dsPIC compiler) I intend to use is TCP/IP LAN to transmit my normal comms between PIC's as well Audio communication. (the dsPIC has the built in cadic coding for audio function)
Andrew
_________________
What has been learnt if you make the same mistake?  |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Wed Aug 30, 2006 7:00 am |
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| Quote: |
My plan is to implement a data transmission between two PICS with basically speakers and microphones.
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There are a very interesting transducer device (named Multi Function) that is a
Speaker & Receiver that work in the audio frequencies, have good sensitivity
and combined with the NE567 -as Ttelmah suggest- as the receiver front end
would be a good choice to start with an acoustical half duplex project.
http://www.shenghui.com/fatcat/upImg/SM15S12R003-A.pdf
It will not be necessary two tones, a single tone will be enough, just start with
a know header tone, - to wake up and synchronize the receiver - following
that, you can start sending the data packets.
Humberto |
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