Re: [Discuss-gnuradio] GNU Radio and Hamlib integration, a step closer

[Eric Blossom]

On Mon, Feb 10, 2003 at 09:30:05AM +0100, Stephane Fillod wrote:
> Hi Matt, Eric, and others,
> 
> I've made some interresting progress lately. I still have no real
> hardware, but using the Hamlib command line interface (rigctl), I'm
> able to set_mode/set_freq of the gnuradio backend and hear the result
> on my sound card!

Great!

> Note: For people wondering what is Hamlib -> http://hamlib.org
> 
> 
> I've added also support in the gnuradio backend to change
> the tuner frequency using another Hamlib backend (microtune, etc.)

One thing to remember is that in GNU Radio land, that "changing the
frequency" may require twisting more than one knob.  E.g., selecting a
narrow band channel while using a wide bandwidth front end could
require adjusting the RF down converter PLL (50kHz steps in our case)
and then making the corresponding adjustment in the software
downconverter.

Given all this, I believe that the appropriate interface is some kind
of remote procedure call (RPC) interface, where the actual
implementation is a function of the signal processing graph currently
instantiated.

> Since GNUradio is compiled without the -DTHREAD option, I 've put
> the MultiTask->process loop in a thread with appropriate locking
> within the gnuradio backend. It works fine, allowing the user app
> linking against Hamlib not having to worry about running the process loop.

Should probably work.  I'm currently revisiting the thread support, so
the interface is likely to change for the better.

> 2 modes are supported so far: (W)FM and USB. However, I'm missing input
> data to test (W)FM, and my USB demodulator is missing an audio filter.
> 

[snip, more later]

> Couple other questions:
> * How is it possible to issue NWO_CONNECT() after the MultiTask->start?
>   I need this when I change mode (from USB to FM for example),
>   and to set_mode on second VFO (ie.channel) while the first one is running.
>   I tried MultiTask->stop() ... MultiTask->start() but GNUradio forbids
>   topology changes (?!)

You can't currently change the topology.  
Yes, it's a problem.  I'm working on it.

> * How is it possible for the source (or offset_fixer) to feed 2 (or
>   more) chains? IOW, to NWO_CONNECT several times an ouput.
>   This is needed if we have 2 channels in parallel.
>   Will I need a mixer before outputting to the VrAudioSink?

No problem connecting multiple modules to a single upstream module.
We do it all the time.  Take a look at the logging code in atsc_rx.cc

> * Is there a web location where I can download some VrFileSource data
>   with different modulations (FM, USB, AM, ..). 5 seconds at 20MS/s
>   would be fine (filesize < 100MB).

I'll put up some samples tomorrow and send email indicating where to
find them.

> That's all for today. Just to let you know, I've written a Hamlib backend
> for the microtune eval board. It's untested, but is supposed to work,
> even with grig (the GUI frontend). If anyone want to test it for me, 
> please let me know, I'll tell how to proceed.

Thanks for your efforts.

> 
> GNU Radio is fun!
> 
> Cheers,
> Stephane - F8CFE

Eric