Topic
3 replies Latest Post - ‏2012-01-31T20:28:19Z by SystemAdmin
KishoreSheikAhamed
KishoreSheikAhamed
2 Posts
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Pinned topic how to register ttyUSB serial interface as PCM with ALSA

‏2012-01-12T13:01:25Z |
I have a serial interface from a telephony modem as ttyUSB0 which gives call voice as digital data in 16bit audio PCM format at 8000hz. HOw to register this interface with ALSA layer for applications to make use of it?
Updated on 2012-01-31T20:28:19Z at 2012-01-31T20:28:19Z by SystemAdmin
  • SystemAdmin
    SystemAdmin
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    Re: how to register ttyUSB serial interface as PCM with ALSA

    ‏2012-01-19T17:03:23Z  in response to KishoreSheikAhamed
    It's likely that the device will require some sort of a driver so that Linux can recognize your device. With that in place Alsa may just pick it up. Can you give more details about the device that you are using?
    • KishoreSheikAhamed
      KishoreSheikAhamed
      2 Posts
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      Re: how to register ttyUSB serial interface as PCM with ALSA

      ‏2012-01-20T05:12:46Z  in response to SystemAdmin
      Thanks for the response cmwaldenatx .

      The device is actually a 3G/HSDPA module with a composite USB interface exposed as 5 virtual serial ports. Each with some function like AT, GPS, GPRS data etc. A linux USB-Serial driver helps here by exposing the device as nodes /dev/ttyUSBx (x=0,...4)

      One of the 5 serial interface gives/takes voice calls as PCM data to the system which the module is interfaced.The interfaced system has its own audio subsystem which is an Android target with linux kernel and ALSA. I am trying to bring up a phone kind of functionality to route this 3G modem voice call data to the existing Android/Linux sound subsystem on the target. Trying this on a ubuntu machine as a test run
      I have tried playing the serial PCM voice data in ubuntu's default speaker/PCM device by opening and buffering the serial port data in user space with Alsalib ALSA-PCM API. But it causes great delay.

      Now is it possible to hook the serial interface as a sound device in the linux kernel or any other ways of doing this?
      • SystemAdmin
        SystemAdmin
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        Re: how to register ttyUSB serial interface as PCM with ALSA

        ‏2012-01-31T20:28:19Z  in response to KishoreSheikAhamed
        I've been doing a little looking into this device and I haven't found any precedent for making use of the audio connection in Linux. Everything seems to be using the TTY connections. Is your goal to use this as an answering machine or voice data? Maybe there's an easier path to your goal.