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Re: [Discuss-gnuradio] Low speed ADC-DAC from Python ?
From: |
Angilberto Muniz Sb |
Subject: |
Re: [Discuss-gnuradio] Low speed ADC-DAC from Python ? |
Date: |
Mon, 3 Apr 2006 12:05:52 -0700 (PDT) |
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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