[Discuss-gnuradio] Working radio Knob

[cswiger]

Gang - Just for the record, one of the Griffin "Power Mate"
knobs looked like a good way to control a radio (for those
of us who enjoy searching for old fashioned dx) as it has
Python script support:

http://www.sowerbutts.com/powermate/powermate.py

and is supported out-of-box in Fedora Core 3.

This quickie script uses the knob to control frequency, volume and
time (file position), the mode being signaled by the light in the
base of the knob. No light means it is in tune mode, solid light is
volume mode, and pulsing light is for time control. Pushing down on
the knob switches modes. One benefit is you can control the radio
while staying focused on another window, plus twisting a knob is just
plain fun.


Sample script schematic:


import pm                       # powermate.py saved as pm.py

def build_graph (freq,scale)

        fg = flow_graph ()      # create graph

        src = gr.file_source () # time controlled with file position

        xlate = gr.freq_xlating_fir_filter_XXX ()  # tune your radio here

        scale = gr.multiply_const_ff () # set volume

        return fg, xlate, scale, src


def main ()

    freq = 3900e3  # initial settings
    scale = .5
    fg = build_graph (freq,scale)

    fg[0].start ()
    pause = 0

    knob = pm.PowerMate()       # get instance
    knob_state = "freq"         # knob mode
    pm.PowerMate.SetLEDState(knob,0,255,1,0,0)  # turn on freq mode lite
    while 1:
      control = pm.PowerMate.WaitForEvent(knob,30) # wait 30s for event
      if control != None:                       # something happened
        if control[3] == 256:                   # button pushed, change
           if control[4] == 1:                  # mode.
              if knob_state == "freq":          # cycle thru modes
                 knob_state = "volume"          # light on solid
                 pm.PowerMate.SetLEDState(knob,255,255,1,0,0)
              else:
                 if knob_state == "volume":
                   knob_state = "time"          # pulsing light
                   pm.PowerMate.SetLEDState(knob,255,264,1,0,1)
                 else:
                   if knob_state == "time":
                     knob_state = "freq"        # light off
                     pm.PowerMate.SetLEDState(knob,0,255,1,0,0)
        if control[3] == 7:                     # knob was turned
           if knob_state == "freq":             # check knob mode
              if control[4] == 1:
                freq += 100                     # up 100 hz
                fg[1].set_center_freq(3.8e6 - freq + 2.5e3)
                print "Listening to", freq
              if control[4] == -1:
                freq -= 100                     # down 100 hz
                fg[1].set_center_freq(3.8e6 - freq + 2.5e3)
                print "Listening to", freq
           if knob_state == "volume":
             if control[4] == 1:
               scale += .1                      # up one volume unit
               fg[2].set_k(scale)
               print "Volume", scale
             if control[4] == -1:
               scale -= .1                      # down one volume unit
               if scale <= 0:                   # unless at zero
                 scale = 0
               fg[2].set_k(scale)
               print "Volume", scale
           if knob_state == "time":
             if control[4] == 1:
               fg[3].seek(1000000,gr.SEEK_CUR)  # fwd in time
             if control[4] == -1:
               fg[3].seek(-1000000,gr.SEEK_CUR) # go back in time



Critique of python style always welcome - Sorry if it looks like BASIC ;)
but it does work.

--Chuck