Re: USB sound adapter for use with Tom's soundmodem?
|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
Do these cheapo USB things with only a Mic input have enough impedance matching to handle a line level input? The reviews seem to be focused on playback. I'm willing to invest the $5 to find out but would rather not waste a week to find out.... 73 /a Andrew Errington wrote: > Hi, > > Spookily enough I have been thinking exactly the same thing. > > The real cheap USB audio devices seem to work in Linux. They're less than > NZ$10 in New Zealand, but I don't actually have one yet. > > Here's a report of someone successfully using one in Linux, with a picture > to show the particular model (there are many USB audio adaptors, but that > particular plastic moulding style seems common): > > http://www.hermann-uwe.de/photoblog/3d-sound-usb-audio-device > > Here's some further information on actually getting the driver running: > > http://www.hermann-uwe.de/blog/playing-audio-on-the-nslu2 > > And here's some general discussion of some different USB audio devices and > issues: > > http://www.nslu2-linux.org/wiki/HowTo/SlugAsAudioPlayer > > Maybe the sampling rate mismatch will be an issue with these devices too. > > :( > > The discussion is targeted at the LinkSys NSLU2 device, but I think the > information can be extrapolated to Linux in general. > > My particular interest is in the LEDs on the USB thingummybob. If they > can be programmed easily then the audio adapter could become a self > contained audio in/out/PTT device (with the LED line controlling a > transistor or something for PTT). I don't yet have a unit to experiment > with (despite them being very cheap) but I think the idea has merit. If > someone else wants to dabble... > > 73, > > Andrew > ZL3AME > > > On Sat, December 13, 2008 16:59, Dave Platt wrote: > >>> Can anyone recommend a USB sound adapter for use with Tom's soundmodem? >>> I'm building an aprsdigi with a newer server I was given that has no >>> motherboard sound and no PCI slots (and no parallel port to do an easy >>> PTT with either:-( I see there's a few choices out there and was >>> hoping one of you had already found one that you could recommend. >>> Thanks. >>> >>> >> I've just been spending some time trying to get the SignaLink USB to >> work with the soundmodem. Have run into a few problems, think I understand >> their cause, and am working on fixes. >> >> First problem noted: the AFSK modem would not even start to receive >> when using soundmodemconfig. The ALSA audio glue complained about the RX >> and TX sample rates being different (and the code has a comment in it to >> the effect of "Make different-rate configurations work, or take them >> out.") >> >> The cause: apparently, the TI USB sound chip in this device publishes >> a different set of sample rates as being available for its input and output >> endpoints. When the device is opened using the "hw:" ALSA specifier (as >> is suggested by the setup dialog), only the actual adapter sample rates >> are available, and since none of them happens to match the sample rate >> that the Soundmodem asks for, the closest-available rates are offered to >> the soundmodem. These offered rates are different and the Soundmodem >> balks. >> >> Workaround: type in "plughw:1,0" as the device to use. The "plughw:" >> module will do software sample-rate conversion when necessary, and in this >> case it allows the Soundmodem to use the sample rate it wants. The same >> rate is used for both the RX and TX channels, and all is well. >> >> At this point, incoming AFSK packets started being decoded reliably >> (as long as the receiver squelch was opened). >> >> >> [Possible alternative - use the ALSA/OSS emulation module, the >> SoundModem OSS interface, and open /dev/dsp1. I don't recommend >> this, as I've observed numerous problems and data glitches in the OSS >> emulation sample rate converter.] >> >> Second problem noted: the soundmodem app would either stop receiving >> and transmitting, or exit abruptly with a "closed pipe" error. >> >> The cause: the ALSA drivers will report a "closed pipe" any time the >> internal audio state machine goes into the XRUN state, which occurs if >> there's a buffer overflow (on receive) or underflow (on transmit). This >> apparently can occur due to timing / race conditions during TX/RX >> turnaround. It's necessary to restart the TX or RX channel with a >> "prepare" call, and it appears that the Soundmodem code doesn't do >> this if an EPIPE error occurs... instead, it bails out and dies. >> >> I haven't yet modified the Soundmodem code to do what's necessary but >> I don't think it'll be difficult. >> >> >> I've had good results with the SignaLink USB using other sound >> packages, for PSK31 and other digital modes, and I believe it'll work well >> for AFSK packet once the driver-interface glitches are dealt with. >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-hams" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at >> http://vger.kernel.org/majordomo-info.html >> >> >> > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-hams" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- To unsubscribe from this list: send the line "unsubscribe linux-hams" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html