> - any device with two audio input/out ports (like two USB audio ports) > and a GPIO port / serial port for switching the radio can be used. a FPU > is needed for codec2 encoding/decoding. > > - between the radio and the modem device, there needs to be a small > interface board. This consists out one single capacitor per > audio-channel (to block DC bias on the audio-signal) and a diode, a > resistor and a transistor to switch the PTT of the radio (add one more > capacitor is switching is done via the serial port instead of the GPIO > port).
You need 3 output signals, but you're requiring 5 or more. Each USB audio device is 2, and the serial port is more. You could do left channels for encoded audio, and right channels for normal audio. Alternately, you could be compatible with fldigi's PTT circuit. This circuit keys the transmitter via a 1 kHz tone in the right audio channel. This type of keying has the advantage of matched latency; the PTT signal doesn't arrive at the radio long before or long after the modem output transitions. Circuit here: http://www.w1hkj.com/FldigiHelp-3.21/PseudoFSK.html Lots of modern PC hardware doesn't even come with a serial port. ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
