[hpsdr] Hermes/Metis Gnuradio update

[Tom McDermott]

Hi Berndt,

The audio sink block must be set to non-blocking mode. The default value is
to block (which causes stuttering). The saved application example should override
the GRC default, but it's the first thing to check. In the non-blocking mode there will be
occasional over or under runs as the Hermes rate and the audio card rate may be
slightly different, but it does not lead to audible distortion. The example SSB 
example decimates down to 16 Ksps to the audio card compensating for the Rx
sample rate.

The GRC Hermes module is full-duplex. The setting of constant zero to the input
connector sets the transmitter to no output. If nothing is connected to the input, GRC
will show an error. Setting TxDrive to zero does not completely kill the transmit signal,
so it is necessary to also send zeros. The Hermes module has a settable switch to
override any Tx symbols and zero them out when receiving, but GRC still needs to
process samples from the input.

I could not find a way to time the symbols to Hermes from gnuradio or detect Tx buffer
overrun, so the software counts received packets from Hermes and schedules transmit
packets to Hermes as a result (the ratio of Tx packets to Rx packets depends on the
number of receivers and the receiver sample rate).

-- Tom, N5EG
 



----- Original Message -----
> From: Berndt Josef Wulf <wulf at ping.net.au>
> To: john <jbden at charter.net>
> Cc: hpsdr at lists.openhpsdr.org
> Sent: Monday, December 10, 2012 5:33 PM
> Subject: Re: [hpsdr] Hermes/Metis Gnuradio update
> 
> ***** High Performance Software Defined Radio Discussion List *****
> 
> G'day,
> 
> I'm using Hermes and also encountered problems in getting a signal.
> Using the example SSB application, I was able to get it to receive after
> switching from 48kHz to 192kHz and back to 48kHz. Perhaps an
> initialisation issue? I also see a lot of underruns, which cause
> stuttering and loss of information.
> 
> Sysinfo: Ubuntu-12.04LTS, x86-64-linux 3.2.0-34-generic, Hermes V2.0
> 
> Questio: What is the purpose of having a constant-block as an input to
> HPSDR-source?
> 
> 73, Berndt
> VK5ABN
> 
> On Mon, 2012-12-10 at 19:21 -0600, john wrote:
>> Also a special thanks to Tom for making gnuradio available. It built
>> fine, but I am not getting any
>> output. I am using Linux Mint 64bit with Metis, Penelope, and Mercury.
>> It my be that I am using a different firmware from what he developed
>> his code with. I am using latest firmware.
>> Thanks for any help.
>> John N4HXL
> 
> 
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