Re: [Discuss-gnuradio] Software AGC

[Eric Blossom]

On Tue, Jan 25, 2005 at 11:48:00AM -0500, Achilleas Anastasopoulos wrote:
> Eric,
> 
> I will get to it ASAP; I can't wait to write my first
> C++ block.

Great!

> However, sometimes there is need for one block to control the gain
> of another block, which cannot be handled by this primitive.
> 
> Some time ago Chuck sent a piece of code that can be modified as
> 
> def build_graph (stuff) :
>    fg = gr.flow_graph ()
>    chan_filter = gr.fir....
>    return fg, chan_filter            <--- returns a tuple
> 
> def main () :
>     tuple = build_graph (stuff)
>     tuple[0].start()                 <--- access 1st item in tuple
>     while True:
>         newtaps = ...generate the new taps
>         time.sleep(5)
>       tuple[1].set_taps (newtaps)  <--- access 2nd item in tuple
> 
> For some reason I cannot get something like this to work with
> GUI applications. Once the app.MainLoop() is invoked, the
> code that follows is not executed. Is there anything like
> the start() method in gui applications?

In gui apps, start is called on your behalf behind the scenes.  You
definitely don't want to block in your gui app.  Schedule a timed call
back.  See wx.FutureCall or wx.Timer in the wxPython docs.

The standard wxPython demos contain a couple of examples of both.
See demo/Timer.py or samples/hangman/hangman.py

Basically you bind a handler to the wx.EVT_TIMER event, then
start a timer runing with wx.Timer. Your handler can change the
taps, or whatever when the timer fires.

Eric