Re: [Discuss-gnuradio] number of blocks in a burst over USB

[Eric Blossom]

On Tue, May 22, 2007 at 12:11:35AM -0400, George Nychis wrote:
> I've tried finding this number throughout code and documentation, but can't 
> seem to hunt it down.  When using  usrp_standard_rx::make(), the last 
> parameter is the number of blocks in a burst.  What's the magic number?
> 
> - George

FYI, it's in usrp_basic.h:

  /*!
   * \param which_board      Which USRP board on usb (not particularly useful; 
use 0)
   * \param fusb_block_size  fast usb xfer block size.  Must be a multiple of 
512. 
   *                         Use zero for a reasonable default.
   * \param fusb_nblocks     number of fast usb URBs to allocate.  Use zero for 
a reasonable default. 
   */
  usrp_basic_rx (int which_board,
                 int fusb_block_size=0,
                 int fusb_nblocks=0,
                 const std::string fpga_filename = "",
                 const std::string firmware_filename = ""
                 );  // throws if trouble


It's not the number of blocks in a burst.  It's the number of blocks
that are allocated for asynchronous tranfers.

I suggest starting with:

  fusb_block_size = 4096
  fusb_nblocks = 16

Though after everything is working and realtime scheduling is
enabled (for the usrp mblocks), we may want to switch to

  fusb_block_size = 1024
  fusb_nblocks = 16

Eric