Re: [Discuss-gnuradio] Low speed ADC-DAC from Python ?

[Angilberto Muniz Sb]

Perfect Eric.

Thank you for the details...

Angilberto.

--- Eric Blossom <address@hidden> wrote:

> On Mon, Apr 03, 2006 at 06:34:24AM -0700, Angilberto
> Muniz Sb wrote:
> > Folks,
> > Is it possible to read/write from/to the low speed
> > ADC/DAC from Python?
> 
> The python interfaces to the usrp are specified in
> gr-usrp/src/usrp1.py.  Check
> usrp/host/lib/usrp_basic.h for the
> missing documentation (sorry about that.  We've got
> a situation that's
> violating the "write once" rule):
> 
> 
>   //! magic value used on alternate register read
> interfaces
>   static const int READ_FAILED = -99999;
> 
>   /*!
>    * \brief Write auxiliary digital to analog
> converter.
>    *
>    * \param which_dboard      [0,1] which d'board
>    *                          N.B., SLOT_TX_A and SLOT_RX_A share the
> same AUX DAC's.
>    *                                  SLOT_TX_B and SLOT_RX_B share the
> same AUX DAC's.
>    * \param which_dac         [2,3] TX slots must use only
> 2 and 3.
>    * \param value             [0,4095]
>    * \returns true iff successful
>    */
>   bool write_aux_dac (int which_board, int
> which_dac, int value);
> 
>   /*!
>    * \brief Read auxiliary analog to digital
> converter.
>    *
>    * \param which_dboard      [0,1] which d'board
>    * \param which_adc         [0,1]
>    * \returns value in the range [0,4095] if
> successful, else READ_FAILED.
>    */
>   int read_aux_adc (int which_dboard, int
> which_adc);
> 
> 
> So from python:
> 
>   d_board = 0   # 0: side A, 1: side B
> 
>   v = u.read_aux_adc(d_board, 0)
>   ok = write_aux_dac(d_board, 2, 2048)
> 
> Be sure to pay attention to the comments above that
> start with N.B.
> You may also want to take a look at the usrp
> schematics if this isn't clear.
> 
> 
> > If possible, what would be a safe rate ?
> 
> It's pretty slow.  You'll need to try it to see how
> fast it'll run on
> your system.  Each read or write is a round trip
> across the USB, plus
> bit banging the SPI bus to talk to the AD9862. 
> There's no clock
> pacing the reads and writes of the the aux
> dac/adc's, so the samples
> won't be evenly spaced.  Most daughterboards that
> use them, use them
> for things like setting an analog gain control, or
> reading back an RSSI
> indication.
> 
> Eric
> 


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