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Dana Myers K6JQ wrote in message ws.com...
R C wrote: I'm working on a telemetry board and wish to include software FSK1200 (MX-614's are getting harder to find). The official Bell 202 spec is out of print and hard to find as well, so I pieced this together from what I can find. Multimon won't decode the output, so I'm likely doing something wrong. This is supposed to be (once it works) my reference implementation before I port it to my telemetry board, so I'm trying to keep it as simple as possible. Any help or suggestions would be appreciated. First - is multimon expecting a properly formatted AX.25 frame? (This code is clearly not creating an HDLC-encoded, AX.25-formatted frame). It looks like you're sending conventional async-encoded ASCII. You need to: That would explain it. I hadn't planned on using AX-25 (TX is the audio subcarrier of an FM ATV camera; no point in packetizing it since no digipeaters would be able to hear it, and unit should never be out of reception range in any case). I had planned on adding framing, checksums and possibly FEC later. I was also trying to keep it as simple as possible initially; encode raw octets and make sure I can decode them. It may be worth adding the HDLC/ax.25; initial basestation will likely be a laptop running soundmodem. Also - I'd avoid the use of transcendental functions (sin()) in the synthesizer loop ; I'd create a lookup table and index it via an integer phase accumulator. Off the top of my head, I'd guess a 16-bit phase accumulator and a 256-element sine array would be plenty. You'd need to precalculate the phase increments for 1200 and 2200 Hz, likely as constants. That is step 2 The target CPU will most likely be a Mega8535 AVR, so conversion to integer is definately indicated. Thanks, R C KG4MVB |
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