DRAWS audio crosstalk? #draws #direwolf


Brian Badger
 

All,

I am currently running direwolf with DRAWS with a radio on channel 0, and nothing connected to the DRAWS board on channel 1.  Direwolf appears to be decoding packets on the channel that isn't connected.  The same packet is heard on both channels, and the channel 1 audio is very very low -- but perfectly readable by Direwolf.

Is this something that we expect would go away when channel 1 is cabled to a different radio, or is this low level crosstalk something expected with the design?  I'm pretty impressed that Direwolf can copy AFSK 1200 at audio level "0", but I don't want to rfgate traffic in the wrong direction.

W0DVM audio level = 64(32/29)   [NONE]   ||||||||_

[0.3] W0DVM>APRS,N0KZ-5:;146.82-CO*111111z3900.20N/10508.00Wr T107.2    Net Tu730<0x0d>

Object, "146.82-CO", Repeater, Generic, (obsolete. Digis should use APNxxx instead)

N 39 00.2000, W 105 08.0000, 146.820 MHz, PL 107.2

.2    Net Tu730

 

W0DVM audio level = 0(0/0)   [NONE]   __|:_____

[1.2] W0DVM>APRS,N0KZ-5:;146.82-CO*111111z3900.20N/10508.00Wr T107.2    Net Tu730<0x0d>

Object, "146.82-CO", Repeater, Generic, (obsolete. Digis should use APNxxx instead)

N 39 00.2000, W 105 08.0000, 146.820 MHz, PL 107.2

.2    Net Tu730


On an unrelated note, I was wondering if anyone has figured out how to activate the HDMI audio out without disabling the UDRC audio device?  When I make the change to /boot/config.txt to enable it, the UDRC audio device disappears on reboot:


# Enable audio (loads snd_bcm2835)

dtparam=audio=on


--
Brian N0KZ




Annaliese McDermond
 


On an unrelated note, I was wondering if anyone has figured out how to activate the HDMI audio out without disabling the UDRC audio device?  When I make the change to /boot/config.txt to enable it, the UDRC audio device disappears on reboot:


# Enable audio (loads snd_bcm2835)

dtparam=audio=on



Make sure your dtparam line comes at the very end of the file, or at least after dtoverlay=draws 

—Anna



--
Brian N0KZ




 

The input is terminated with 100kohms, so if there is no radio connected there is sufficient crosstalk for DIREWOLF to decode a few packets, but it has to work really hard to do it. You will see signal levels of “0” and you may even see DIREWOLF run out of CPU.

One of our UDRC users reported that the Analog input was 10-12dB quieter than other boards he had used, which allows decode down to the noise floor.

Turn off the unused channel.

Bryan K7UDR


Basil Gunn
 

Also I noticed about a 2 second delay before the onset of audio when
using HDMI for audio. It varies depending on device.

I fixed this in Xastir by using the following in
File > Configure > Configure Audio Alarms : Audio Play command

aplay -D "plughw:0,1" silence.wav

Notes here: Look for Configure Audio
https://github.com/nwdigitalradio/n7nix/tree/master/xastir
silence file here:
https://github.com/nwdigitalradio/n7nix/blob/master/xastir/silence.wav

/Basil

On an unrelated note, I was wondering if anyone has figured out how
to activate the HDMI audio out without disabling the UDRC audio
device? When I make the change to /boot/config.txt to enable it, the
UDRC audio device disappears on reboot:

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

Make sure your dtparam line comes at the very end of the file, or at least after dtoverlay=draws

—Anna
--
Brian N0KZ


Brian Badger
 

All of that is in line with my expectation, but I haven’t figured out the “turn off the unused channel”. When I remove channel 1 it still comes up as 1200 baud by default. That’s exactly how I found the issue.


Brian N0KZ

On Dec 12, 2018, at 4:32 PM, Bryan Hoyer <bhhoyer@gmail.com> wrote:

The input is terminated with 100kohms, so if there is no radio connected there is sufficient crosstalk for DIREWOLF to decode a few packets, but it has to work really hard to do it. You will see signal levels of “0” and you may even see DIREWOLF run out of CPU.

One of our UDRC users reported that the Analog input was 10-12dB quieter than other boards he had used, which allows decode down to the noise floor.

Turn off the unused channel.

Bryan K7UDR






Brian Badger
 

# Additional overlays and parameters are documented /boot/overlays/README

 

force_turbo=1

dtoverlay=draws

 

# Enable audio (loads snd_bcm2835)

dtparam=audio=on



results in:

Audio device for both receive and transmit: plughw:CARD=udrc,DEV=0  (channel 0)

ALSA lib pcm_hw.c:1713:(_snd_pcm_hw_open) Invalid value for card

Could not open audio device plughw:CARD=udrc,DEV=0 for input

No such device

 

Pointless to continue without audio device.