pic serial data

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pic serial data

Post by Pittpablo » Sun Dec 29, 2002 11:08 am

can anyone think of a way to take serial data into a pic and convert it from logic pulses to audio (serial data) tones to be transmitted via amateur radio, say using two pics?<p>i found a modem chip (mx614) but it is very hard to purchase. i thought using two pics, i could eliminate the modem but i cant seem to think of a way.<p>thanks for the help,

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Re: pic serial data

Post by ljbeng » Mon Jan 13, 2003 2:42 pm

The pic could convert to DTMF audio out and on the other end the CD22204 DTMF decoder could be used and also be connected to the other PIC. Serial rate may have to slow down considerably but I have used DTMF to send serial data over the phone, very slow but it worked. About 100 Baud was all I needed and I made it go slow to keep error minimal.

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Re: pic serial data

Post by russlk » Mon Jan 13, 2003 2:49 pm

The Radio Shack TRS-80 computer saved data on an audio tape recorder. There must be info out there on how they did it.

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Re: pic serial data

Post by larussell » Tue Jan 14, 2003 1:59 pm

How about a VCO (voltage controlled oscillator) set to go between the two frequencies based on high or low input? Or two 555s set to the two frequencies with gates to choose between them based on high or low input?<p>The modems are hard to find because no one uses them anymore; the hams use software driven PC soundcards to do the job. You can download freeware to do the standard formats like RTTY or SSTV. One popular program is called MMSSTV and you can do a search to find it. You might also check eBay if you need a hardware solution.

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Re: pic serial data

Post by chessman » Wed Jan 15, 2003 9:24 am

I abandoned a project I was working on about a year ago, a high speed long-range data network, because i lacked the knowledge. <p> I do know TI makes a chip that will recieve digital serial data, modulate it, and output an amplifier-ready digital data stream to be broadcasted. I'm not sure the specifics, and obviously it requires the right sink circuits and local oscillators (IF and carrier, as well as maybe one or two others i think).
I don't remember the part number, but maybe this will point you in the right direction...
Oh yeah, one final thing. I think the chip is in TQFP packaging, and I don't know your capabilities so that may or may not be a limiting factor.<p>~Kyle

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