On Mon, May 21, 2007 at 04:19:58PM -0400, Steven Clark wrote: > If I need pin-level access to the DAC chip, sink_s is my only option AFAIK. > I understand that it's interleaved I&Q, don't worry about that. > My original questions remain. > > On 5/21/07, Eric Blossom <[EMAIL PROTECTED]> wrote: > > > >On Mon, May 21, 2007 at 10:48:04AM -0400, Steven Clark wrote: > >> Hi all- > >> > >> Several quick questions. > >> 1) For usrp sink_s, which bit of the short activates the MSB of the DAC > >> chip? I.e., if I send 0bABCDEFGH IJKLMNOP, where each letter is either a > >1 > >> or a 0, which letter matches the MSB?
What you sent to sink_s doesn't go directly to the DACs, but rather is first interpolated and possibly upconverted. See http://gnuradio.org/trac/wiki/UsrpRfxDiagrams The DACs run at a constant 128 MS/s. They are fed from the FPGA at 32 MS/s, and are interpolated by a factor of 4 in the AD9862. See the AD9862 datasheet for details. The I & Q data written to sink_s should be 16-bit 2's-complement host-endian data in the range -32768 to 32767. The max and minimum values that make sense actually depend somewhat on the associated RF daughterboard. Analog clipping may occur at values smaller in magnitude than +/- 32,767. Eric _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
