Re: Troubleshooting ThumbDV HW AMBE chip with Analog_Bridge


Steve N4IRS
 

David,
I will consider adding the text to the howto. One change is that the AMBE chip is not sensitive to voltage sags. The ThumbDV is sensitive to voltage sags.

Steve N4IRS


On 9/7/19 12:59 AM, David Ranch wrote:
Hello Steve,

    echo 1 > /sys/bus/usb-serial/devices/ttyUSB0/latency_timer

I'm happy to report that this resolved my issue and the audio quality issue is resolved!  If I can make a recommendation, on page 16 of https://docs.google.com/document/d/1eN50Csr29eAprBu7eKA0Bfa2XUcsXw5iktY1Ey-Qjkg/edit , consider adding tothe "Insert vocoder discussion here" section.  Something like:

   - Enable the "Project 25 IMBE Encoder/Decoder Fixed-Point implementation" codec

    This is the default setting and generally has good audio quality

    Analog_Bridge.ini

          [GENERAL]
          decoderFallBack = true
          useEmulator = false
          [DV3000]
          ;server = /dev/ttyUSB0                 ; Device of DV3000U on this machine
          ;port = 460800                         ; Baud rate of the dongle
          ;serial = true                         ; Use serial (DV3000U) or IP


   - Enable the md380-emu codec

    This has good audio quality (possibly better than the IMBE software vocoder):

       Document how the md380-emu process will be started

       Analog_Bridge.ini

          [GENERAL]
          decoderFallBack = false
          useEmulator = true
          [DV3000]
          ;server = /dev/ttyUSB0                 ; Device of DV3000U on this machine
          ;port = 460800                         ; Baud rate of the dongle
          ;serial = true                         ; Use serial (DV3000U) or IP


   - Enable HW AMBE codec

    This is the default setting and generally has good audio quality (possibly better than the IMBE software vocoder):


      - Connect the HW device directly to your computer (no USB hubs if possible)

      - Edit the Analog_Bridge.ini
          [GENERAL]
          decoderFallBack = false
          useEmulator = false
          [DV3000]
          server = /dev/ttyUSB0                 ; Device of DV3000U on this machine
          port = 460800                         ; Baud rate of the dongle
          serial = true                         ; Use serial (DV3000U) or IP



      - If used with a Raspberry Pi and you experience audio issues:

         - When connected to the Raspberry Pi, run the "dmesg" command and confirm which serial port it's beeing
          seen as.  The default is /dev/ttyUSB0 unless that device is already in use

         - Make sure that the serial RX/TX LEDs are lighting up on the USB device when receiving / transmitting signals

         - You might need to change your USB latency with:
          echo 1 | sudo tee /sys/bus/usb-serial/devices/ttyUSB0/latency_timer

         - Use a proper power supply for your Rpi as the AMBE chips are reknown for being very sensitive to
          voltage sags

--David
KI6ZHD

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