Re: [Discuss-gnuradio] gain setting in osmosdr block

[Andy Walls]

> From:         Dirk Gorissen
> Date:         Thu, 3 May 2018 22:25:09 +0100
> 
> Hello,
> 
> Im using an airspy mini through the osmosdr block. I would like
> control over the 3 gains the airspy has (IF, Mixer, LNA) but the
> osmossdr block does not seem to expose this. Is there a workaround?

The C++ and Python interfaces look like they support setting them:

https://github.com/osmocom/gr-osmosdr/blob/master/include/osmosdr/source.h#L185
https://github.com/osmocom/gr-osmosdr/blob/master/lib/source_impl.h#L59
https://github.com/osmocom/gr-osmosdr/blob/master/lib/source_impl.cc#L667
https://github.com/osmocom/gr-osmosdr/blob/master/lib/source_iface.h#L165
https://github.com/osmocom/gr-osmosdr/blob/master/lib/airspy/airspy_source_c.h#L108
https://github.com/osmocom/gr-osmosdr/blob/master/lib/airspy/airspy_source_c.cc#L533

but the GRC file for the GUI block doesn't appear to let you call these
from GRC.

Workaround:

In the Python script generated by GRC, you should be able to make the
following calls where appropriate:

        # Turn off hardware AGC
        source_block_instance.set_gain_mode(False, 0)

        # Set gains
        source_block_instance.set_gain(desired_lna_gain, 'LNA', 0)
        source_block_instance.set_gain(desired_mix_gain, 'MIX', 0)
        
source_block_instance.set_gain(desired_if_gain,  'IF',  0)


The proper fix, is to fix this GRC block XML generator script to
present a tab for input of named gains, and to add callbacks for those
named gains:

https://github.com/osmocom/gr-osmosdr/blob/master/grc/gen_osmosdr_blocks.py


Regards,
Andy

> Cheers
> Dirk