[Discuss-gnuradio] Hamlib and microtune eval board

[Stephane Fillod]

Hi there,

I try to see clearly how Hamlib could interact with GNUradio.
So far, I see 2 ways:

1. GNUradio uses Hamlib to change the frequency of the tuner generating
  the IF. IOW, make a "hamlib backend" out of the microtune_eval_board
  class.

2. Hamlib implements a real SDR (using gnuradio lib)

At first, when Matt contacted me, I only thought of 2. But we can have
1. for gnuradio applications (eg. fm_demod2.cc), and also 1.+2. for Hamlib 
applications like grig.

So I have some questions to implement 1.:
* What is the parallel port pinout of the microtune eval board? Is there
  any protocol documentation ? As I understand, this is
  bit-banged I2C. Is it possible to use Linux kernel i2c-dev support?
  If not, I would prefer using the ppdev than direct inb/outb which
  requires root privileges (on x86 for ioperm).
 
* talking about class microtune_4937 (src/gnu/lib/grio/microtune_4937.h):
  - IMHO, set_RF_freq should only return when PLL is locked.
    Is the pll_locked_p method really needed?
  - get_output_freq: this is the center frequency of the IF, right ?
    I'm a bit worried, because if I replace the the microtune_eval_board
    class and its set_RF_freq by rig_set_freq(), Hamlib has no such
    information about output_freq. With the same receiver, some people 
    would tap the AF with a sound card, some other may steal the rig 
    internal IF using an acquisition board, etc.  Do you see what I mean?

For the moment, I plan to add support in Hamlib for the
microtune_eval_bord. This way, a simple C program will be able to
rig_set_freq() to set the frequency. Note, I don't have the hardware so
I'll ask one of you to test it.

Then, I'd like to go next with a real case I can test myself. Do you think
it's possible with a sound card (44KHz sampling in mono, so 22KHz real
bandwidth) to make the src/gnu/examples/nbfm.cc example to work?
The "IF" source would come from the AF of a regular transceiver (no idea 
of its bandwidth, I hope more than 3KHz). Do you think it's achievable?


Cheers
Stephane