Merged r11377:11390 from jcorgan/usrp-headers in to trunk.

* Public USRP(1) header files are now in their own source directory
  and install into $(includedir)/usrp.  This was done to avoid name
  clashes in the top-level include directory.

  Only users who are developing directly to libusrp in C++ are
  affected; the GNU Radio C++ and Python APIs are unchanged.

  The simple change required by this update is to change:

  #include <usrp_*.h> 

  to #include 

  <usrp/usrp_*.h> 

  ...in your source code.

* Removed usrp-inband code from tree (put into limbo directory.)
  This code has become unmaintained and has started to suffer
  from bitrot.  A checkpoint tag has been made for anyone still
  needing to use it:

  http://gnuradio.org/svn/gnuradio/tags/checkpoints/trunk-20090708-pre-usrp-reorg

  The plan during the 3.2->3.3 development cycle is to replace the
  functions done by the in-band code with extensions to the existing
  gr-usrp blocks using the new message passing architecture.

  The USRP hardware FPGA code that provided the inband interface
  has not been removed; however, it too has become unmaintained and
  will likely be rewritten/replaced during the 3.3 timeframe.

The trunk passes distcheck.




git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@11394 221aa14e-8319-0410-a670-987f0aec2ac5

1 files changed, 1357 insertions, 0 deletions

diff --git a/usrp/host/lib/usrp_prims.cc b/usrp/host/lib/usrp_prims.cc
new file mode 100644
index 000000000..3d87d2459
--- /dev/null
+++ b/usrp/host/lib/usrp_prims.cc
@@ -0,0 +1,1357 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2003,2004,2006,2009 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "usrp/usrp_prims.h"
+#include "usrp_commands.h"
+#include "usrp_ids.h"
+#include "usrp_i2c_addr.h"
+#include "fpga_regs_common.h"
+#include "fpga_regs_standard.h"
+#include <usb.h>
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <time.h>		// FIXME should check with autoconf (nanosleep)
+#include <algorithm>
+#include <ad9862.h>
+#include <assert.h>
+
+extern "C" {
+#include "md5.h"
+};
+
+#define VERBOSE 0
+
+using namespace ad9862;
+
+static const int FIRMWARE_HASH_SLOT	= 0;
+static const int FPGA_HASH_SLOT 	= 1;
+
+static const int hash_slot_addr[2] = {
+  USRP_HASH_SLOT_0_ADDR,
+  USRP_HASH_SLOT_1_ADDR
+};
+
+static const char *default_firmware_filename = "std.ihx";
+static const char *default_fpga_filename     = "std_2rxhb_2tx.rbf";
+
+#include "std_paths.h"
+#include <stdio.h>
+
+static char *
+find_file (const char *filename, int hw_rev)
+{
+  const char **sp = std_paths;
+  static char path[1000];
+  char *s;
+
+  s = getenv("USRP_PATH");
+  if (s) {
+    snprintf (path, sizeof (path), "%s/rev%d/%s", s, hw_rev, filename);
+    if (access (path, R_OK) == 0)
+      return path;
+  }
+
+  while (*sp){
+    snprintf (path, sizeof (path), "%s/rev%d/%s", *sp, hw_rev, filename);
+    if (access (path, R_OK) == 0)
+      return path;
+    sp++;
+  }
+  return 0;
+}
+
+static const char *
+get_proto_filename(const std::string user_filename, const char *env_var, const char *def)
+{
+  if (user_filename.length() != 0)
+    return user_filename.c_str();
+
+  char *s = getenv(env_var);
+  if (s && *s)
+    return s;
+
+  return def;
+}
+
+
+static void power_down_9862s (struct usb_dev_handle *udh);
+
+void
+usrp_one_time_init ()
+{
+  static bool first = true;
+
+  if (first){
+    first = false;
+    usb_init ();			// usb library init
+    usb_find_busses ();
+    usb_find_devices ();
+  }
+}
+
+void
+usrp_rescan ()
+{
+  usb_find_busses ();
+  usb_find_devices ();
+}
+
+
+// ----------------------------------------------------------------
+// Danger, big, fragile KLUDGE.  The problem is that we want to be
+// able to get from a usb_dev_handle back to a usb_device, and the
+// right way to do this is buried in a non-installed include file.
+
+static struct usb_device *
+dev_handle_to_dev (usb_dev_handle *udh)
+{
+  struct usb_dev_handle_kludge {
+    int			 fd;
+    struct usb_bus	*bus;
+    struct usb_device	*device;
+  };
+
+  return ((struct usb_dev_handle_kludge *) udh)->device;
+}
+
+// ----------------------------------------------------------------
+
+/*
+ * q must be a real USRP, not an FX2.  Return its hardware rev number.
+ */
+int
+usrp_hw_rev (struct usb_device *q)
+{
+  return q->descriptor.bcdDevice & 0x00FF;
+}
+
+/*
+ * q must be a real USRP, not an FX2.  Return true if it's configured.
+ */
+static bool
+_usrp_configured_p (struct usb_device *q)
+{
+  return (q->descriptor.bcdDevice & 0xFF00) != 0;
+}
+
+bool
+usrp_usrp_p (struct usb_device *q)
+{
+  return (q->descriptor.idVendor == USB_VID_FSF
+	  && q->descriptor.idProduct == USB_PID_FSF_USRP);
+}
+
+bool
+usrp_fx2_p (struct usb_device *q)
+{
+  return (q->descriptor.idVendor == USB_VID_CYPRESS
+	  && q->descriptor.idProduct == USB_PID_CYPRESS_FX2);
+}
+
+bool
+usrp_usrp0_p (struct usb_device *q)
+{
+  return usrp_usrp_p (q) && usrp_hw_rev (q) == 0;
+}
+
+bool
+usrp_usrp1_p (struct usb_device *q)
+{
+  return usrp_usrp_p (q) && usrp_hw_rev (q) == 1;
+}
+
+bool
+usrp_usrp2_p (struct usb_device *q)
+{
+  return usrp_usrp_p (q) && usrp_hw_rev (q) == 2;
+}
+
+
+bool
+usrp_unconfigured_usrp_p (struct usb_device *q)
+{
+  return usrp_usrp_p (q) && !_usrp_configured_p (q);
+}
+
+bool
+usrp_configured_usrp_p (struct usb_device *q)
+{
+  return usrp_usrp_p (q) && _usrp_configured_p (q);
+}
+
+// ----------------------------------------------------------------
+
+struct usb_device *
+usrp_find_device (int nth, bool fx2_ok_p)
+{
+  struct usb_bus *p;
+  struct usb_device *q;
+  int	 n_found = 0;
+
+  usrp_one_time_init ();
+  
+  p = usb_get_busses();
+  while (p != NULL){
+    q = p->devices;
+    while (q != NULL){
+      if (usrp_usrp_p (q) || (fx2_ok_p && usrp_fx2_p (q))){
+	if (n_found == nth)	// return this one
+	  return q;
+	n_found++;		// keep looking
+      }
+      q = q->next;
+    }
+    p = p->next;
+  }
+  return 0;	// not found
+}
+
+static struct usb_dev_handle *
+usrp_open_interface (struct usb_device *dev, int interface, int altinterface)
+{
+  struct usb_dev_handle *udh = usb_open (dev);
+  if (udh == 0)
+    return 0;
+
+  if (dev != dev_handle_to_dev (udh)){
+    fprintf (stderr, "%s:%d: internal error!\n", __FILE__, __LINE__);
+    abort ();
+  }
+
+#if defined(_WIN32) || defined(__WIN32__) || defined(__CYGWIN__)
+  // There's no get get_configuration function, and with some of the newer kernels
+  // setting the configuration, even if to the same value, hoses any other processes
+  // that have it open.  Hence we opt to not set it at all (We've only
+  // got a single configuration anyway).  This may hose the win32 stuff...
+
+  // Appears to be required for libusb-win32 and Cygwin -- dew 09/20/06
+  if (usb_set_configuration (udh, 1) < 0){
+    /*
+     * Ignore this error.  
+     *
+     * Seems that something changed in drivers/usb/core/devio.c:proc_setconfig such that
+     * it returns -EBUSY if _any_ of the interfaces of a device are open.
+     * We've only got a single configuration, so setting it doesn't even seem
+     * like it should be required.
+     */
+  }
+#endif
+
+  if (usb_claim_interface (udh, interface) < 0){
+    fprintf (stderr, "%s:usb_claim_interface: failed interface %d\n", __FUNCTION__,interface);
+    fprintf (stderr, "%s\n", usb_strerror());
+    usb_close (udh);
+    return 0;
+  }
+
+  if (usb_set_altinterface (udh, altinterface) < 0){
+    fprintf (stderr, "%s:usb_set_alt_interface: failed\n", __FUNCTION__);
+    fprintf (stderr, "%s\n", usb_strerror());
+    usb_release_interface (udh, interface);
+    usb_close (udh);
+    return 0;
+  }
+
+  return udh;
+}
+
+struct usb_dev_handle *
+usrp_open_cmd_interface (struct usb_device *dev)
+{
+  return usrp_open_interface (dev, USRP_CMD_INTERFACE, USRP_CMD_ALTINTERFACE);
+}
+
+struct usb_dev_handle *
+usrp_open_rx_interface (struct usb_device *dev)
+{
+  return usrp_open_interface (dev, USRP_RX_INTERFACE, USRP_RX_ALTINTERFACE);
+}
+
+struct usb_dev_handle *
+usrp_open_tx_interface (struct usb_device *dev)
+{
+  return usrp_open_interface (dev, USRP_TX_INTERFACE, USRP_TX_ALTINTERFACE);
+}
+
+bool
+usrp_close_interface (struct usb_dev_handle *udh)
+{
+  // we're assuming that closing an interface automatically releases it.
+  return usb_close (udh) == 0;
+}
+
+// ----------------------------------------------------------------
+// write internal ram using Cypress vendor extension
+
+static bool
+write_internal_ram (struct usb_dev_handle *udh, unsigned char *buf,
+		    int start_addr, size_t len)
+{
+  int addr;
+  int n;
+  int a;
+  int quanta = MAX_EP0_PKTSIZE;
+
+  for (addr = start_addr; addr < start_addr + (int) len; addr += quanta){
+    n = len + start_addr - addr;
+    if (n > quanta)
+      n = quanta;
+
+    a = usb_control_msg (udh, 0x40, 0xA0,
+			 addr, 0, (char *)(buf + (addr - start_addr)), n, 1000);
+
+    if (a < 0){
+      fprintf(stderr,"write_internal_ram failed: %s\n", usb_strerror());
+      return false;
+    }
+  }
+  return true;
+}
+
+// ----------------------------------------------------------------
+// whack the CPUCS register using the upload RAM vendor extension
+
+static bool
+reset_cpu (struct usb_dev_handle *udh, bool reset_p)
+{
+  unsigned char v;
+
+  if (reset_p)
+    v = 1;		// hold processor in reset
+  else
+    v = 0;	        // release reset
+
+  return write_internal_ram (udh, &v, 0xE600, 1);
+}
+
+// ----------------------------------------------------------------
+// Load intel format file into cypress FX2 (8051)
+
+static bool
+_usrp_load_firmware (struct usb_dev_handle *udh, const char *filename,
+		     unsigned char hash[USRP_HASH_SIZE])
+{
+  FILE	*f = fopen (filename, "ra");
+  if (f == 0){
+    perror (filename);
+    return false;
+  }
+
+  if (!reset_cpu (udh, true))	// hold CPU in reset while loading firmware
+    goto fail;
+
+  
+  char s[1024];
+  int length;
+  int addr;
+  int type;
+  unsigned char data[256];
+  unsigned char checksum, a;
+  unsigned int b;
+  int i;
+
+  while (!feof(f)){
+    fgets(s, sizeof (s), f); /* we should not use more than 263 bytes normally */
+    if(s[0]!=':'){
+      fprintf(stderr,"%s: invalid line: \"%s\"\n", filename, s);
+      goto fail;
+    }
+    sscanf(s+1, "%02x", &length);
+    sscanf(s+3, "%04x", &addr);
+    sscanf(s+7, "%02x", &type);
+
+    if(type==0){
+
+      a=length+(addr &0xff)+(addr>>8)+type;
+      for(i=0;i<length;i++){
+	sscanf (s+9+i*2,"%02x", &b);
+	data[i]=b;
+	a=a+data[i];
+      }
+
+      sscanf (s+9+length*2,"%02x", &b);
+      checksum=b;
+      if (((a+checksum)&0xff)!=0x00){
+	fprintf (stderr, "  ** Checksum failed: got 0x%02x versus 0x%02x\n", (-a)&0xff, checksum);
+	goto fail;
+      }
+      if (!write_internal_ram (udh, data, addr, length))
+	goto fail;
+    }
+    else if (type == 0x01){      // EOF
+      break;
+    }
+    else if (type == 0x02){
+      fprintf(stderr, "Extended address: whatever I do with it?\n");
+      fprintf (stderr, "%s: invalid line: \"%s\"\n", filename, s);
+      goto fail;
+    }
+  }
+
+  // we jam the hash value into the FX2 memory before letting
+  // the cpu out of reset.  When it comes out of reset it
+  // may renumerate which will invalidate udh.
+
+  if (!usrp_set_hash (udh, FIRMWARE_HASH_SLOT, hash))
+    fprintf (stderr, "usrp: failed to write firmware hash slot\n");
+
+  if (!reset_cpu (udh, false))		// take CPU out of reset
+    goto fail;
+
+  fclose (f);
+  return true;
+
+ fail:
+  fclose (f);
+  return false;
+}
+
+// ----------------------------------------------------------------
+// write vendor extension command to USRP
+
+static int
+write_cmd (struct usb_dev_handle *udh,
+	   int request, int value, int index,
+	   unsigned char *bytes, int len)
+{
+  int	requesttype = (request & 0x80) ? VRT_VENDOR_IN : VRT_VENDOR_OUT;
+
+  int r = usb_control_msg (udh, requesttype, request, value, index,
+			   (char *) bytes, len, 1000);
+  if (r < 0){
+    // we get EPIPE if the firmware stalls the endpoint.
+    if (errno != EPIPE)
+      fprintf (stderr, "usb_control_msg failed: %s\n", usb_strerror ());
+  }
+
+  return r;
+}
+
+// ----------------------------------------------------------------
+// load fpga
+
+static bool
+_usrp_load_fpga (struct usb_dev_handle *udh, const char *filename,
+		 unsigned char hash[USRP_HASH_SIZE])
+{
+  bool ok = true;
+
+  FILE	*fp = fopen (filename, "rb");
+  if (fp == 0){
+    perror (filename);
+    return false;
+  }
+
+  unsigned char buf[MAX_EP0_PKTSIZE];	// 64 is max size of EP0 packet on FX2
+  int n;
+
+  usrp_set_led (udh, 1, 1);		// led 1 on
+
+
+  // reset FPGA (and on rev1 both AD9862's, thus killing clock)
+  usrp_set_fpga_reset (udh, 1);		// hold fpga in reset
+
+  if (write_cmd (udh, VRQ_FPGA_LOAD, 0, FL_BEGIN, 0, 0) != 0)
+    goto fail;
+  
+  while ((n = fread (buf, 1, sizeof (buf), fp)) > 0){
+    if (write_cmd (udh, VRQ_FPGA_LOAD, 0, FL_XFER, buf, n) != n)
+      goto fail;
+  }
+
+  if (write_cmd (udh, VRQ_FPGA_LOAD, 0, FL_END, 0, 0) != 0)
+    goto fail;
+  
+  fclose (fp);
+
+  if (!usrp_set_hash (udh, FPGA_HASH_SLOT, hash))
+    fprintf (stderr, "usrp: failed to write fpga hash slot\n");
+
+  // On the rev1 USRP, the {tx,rx}_{enable,reset} bits are
+  // controlled over the serial bus, and hence aren't observed until
+  // we've got a good fpga bitstream loaded.
+
+  usrp_set_fpga_reset (udh, 0);		// fpga out of master reset
+
+  // now these commands will work
+  
+  ok &= usrp_set_fpga_tx_enable (udh, 0);
+  ok &= usrp_set_fpga_rx_enable (udh, 0);
+
+  ok &= usrp_set_fpga_tx_reset (udh, 1);	// reset tx and rx paths
+  ok &= usrp_set_fpga_rx_reset (udh, 1);
+  ok &= usrp_set_fpga_tx_reset (udh, 0);	// reset tx and rx paths
+  ok &= usrp_set_fpga_rx_reset (udh, 0);
+
+  if (!ok)
+    fprintf (stderr, "usrp: failed to reset tx and/or rx path\n");
+
+  // Manually reset all regs except master control to zero.
+  // FIXME may want to remove this when we rework FPGA reset strategy.
+  // In the mean while, this gets us reproducible behavior.
+  for (int i = 0; i < FR_USER_0; i++){
+    if (i == FR_MASTER_CTRL)
+      continue;
+    usrp_write_fpga_reg(udh, i, 0);
+  }
+
+  power_down_9862s (udh);		// on the rev1, power these down!
+  usrp_set_led (udh, 1, 0);		// led 1 off
+
+  return true;
+
+ fail:
+  power_down_9862s (udh);		// on the rev1, power these down!
+  fclose (fp);
+  return false;
+}
+
+// ----------------------------------------------------------------
+
+bool 
+usrp_set_led (struct usb_dev_handle *udh, int which, bool on)
+{
+  int r = write_cmd (udh, VRQ_SET_LED, on, which, 0, 0);
+
+  return r == 0;
+}
+
+bool
+usrp_set_hash (struct usb_dev_handle *udh, int which,
+	       const unsigned char hash[USRP_HASH_SIZE])
+{
+  which &= 1;
+  
+  // we use the Cypress firmware down load command to jam it in.
+  int r = usb_control_msg (udh, 0x40, 0xa0, hash_slot_addr[which], 0,
+			   (char *) hash, USRP_HASH_SIZE, 1000);
+  return r == USRP_HASH_SIZE;
+}
+
+bool
+usrp_get_hash (struct usb_dev_handle *udh, int which, 
+	       unsigned char hash[USRP_HASH_SIZE])
+{
+  which &= 1;
+  
+  // we use the Cypress firmware upload command to fetch it.
+  int r = usb_control_msg (udh, 0xc0, 0xa0, hash_slot_addr[which], 0,
+			   (char *) hash, USRP_HASH_SIZE, 1000);
+  return r == USRP_HASH_SIZE;
+}
+
+static bool
+usrp_set_switch (struct usb_dev_handle *udh, int cmd_byte, bool on)
+{
+  return write_cmd (udh, cmd_byte, on, 0, 0, 0) == 0;
+}
+
+
+static bool
+usrp1_fpga_write (struct usb_dev_handle *udh,
+		  int regno, int value)
+{
+  // on the rev1 usrp, we use the generic spi_write interface
+
+  unsigned char buf[4];
+
+  buf[0] = (value >> 24) & 0xff;	// MSB first
+  buf[1] = (value >> 16) & 0xff;
+  buf[2] = (value >>  8) & 0xff;
+  buf[3] = (value >>  0) & 0xff;
+  
+  return usrp_spi_write (udh, 0x00 | (regno & 0x7f),
+			 SPI_ENABLE_FPGA,
+			 SPI_FMT_MSB | SPI_FMT_HDR_1,
+			 buf, sizeof (buf));
+}
+
+static bool
+usrp1_fpga_read (struct usb_dev_handle *udh,
+		 int regno, int *value)
+{
+  *value = 0;
+  unsigned char buf[4];
+
+  bool ok = usrp_spi_read (udh, 0x80 | (regno & 0x7f),
+			   SPI_ENABLE_FPGA,
+			   SPI_FMT_MSB | SPI_FMT_HDR_1,
+			   buf, sizeof (buf));
+
+  if (ok)
+    *value = (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3];
+
+  return ok;
+}
+
+
+bool
+usrp_write_fpga_reg (struct usb_dev_handle *udh, int reg, int value)
+{
+  switch (usrp_hw_rev (dev_handle_to_dev (udh))){
+  case 0:			// not supported ;)
+    abort();	
+
+  default:
+    return usrp1_fpga_write (udh, reg, value);
+  }
+}
+
+bool
+usrp_read_fpga_reg (struct usb_dev_handle *udh, int reg, int *value)
+{
+  switch (usrp_hw_rev (dev_handle_to_dev (udh))){
+  case 0:		// not supported ;)
+    abort();
+    
+  default:
+    return usrp1_fpga_read (udh, reg, value);
+  }
+}
+
+bool 
+usrp_set_fpga_reset (struct usb_dev_handle *udh, bool on)
+{
+  return usrp_set_switch (udh, VRQ_FPGA_SET_RESET, on);
+}
+
+bool 
+usrp_set_fpga_tx_enable (struct usb_dev_handle *udh, bool on)
+{
+  return usrp_set_switch (udh, VRQ_FPGA_SET_TX_ENABLE, on);
+}
+
+bool 
+usrp_set_fpga_rx_enable (struct usb_dev_handle *udh, bool on)
+{
+  return usrp_set_switch (udh, VRQ_FPGA_SET_RX_ENABLE, on);
+}
+
+bool 
+usrp_set_fpga_tx_reset (struct usb_dev_handle *udh, bool on)
+{
+  return usrp_set_switch (udh, VRQ_FPGA_SET_TX_RESET, on);
+}
+
+bool 
+usrp_set_fpga_rx_reset (struct usb_dev_handle *udh, bool on)
+{
+  return usrp_set_switch (udh, VRQ_FPGA_SET_RX_RESET, on);
+}
+
+
+// ----------------------------------------------------------------
+// conditional load stuff
+
+static bool
+compute_hash (const char *filename, unsigned char hash[USRP_HASH_SIZE])
+{
+  assert (USRP_HASH_SIZE == 16);
+  memset (hash, 0, USRP_HASH_SIZE);
+
+  FILE *fp = fopen (filename, "rb");
+  if (fp == 0){
+    perror (filename);
+    return false;
+  }
+  int r = md5_stream (fp, hash);
+  fclose (fp);
+  
+  return r == 0;
+}
+
+static usrp_load_status_t
+usrp_conditionally_load_something (struct usb_dev_handle *udh,
+				   const char *filename,
+				   bool force,
+				   int slot,
+				   bool loader (struct usb_dev_handle *,
+						const char *,
+						unsigned char [USRP_HASH_SIZE]))
+{
+  unsigned char file_hash[USRP_HASH_SIZE];
+  unsigned char usrp_hash[USRP_HASH_SIZE];
+  
+  if (access (filename, R_OK) != 0){
+    perror (filename);
+    return ULS_ERROR;
+  }
+
+  if (!compute_hash (filename, file_hash))
+    return ULS_ERROR;
+
+  if (!force
+      && usrp_get_hash (udh, slot, usrp_hash)
+      && memcmp (file_hash, usrp_hash, USRP_HASH_SIZE) == 0)
+    return ULS_ALREADY_LOADED;
+
+  bool r = loader (udh, filename, file_hash);
+
+  if (!r)
+    return ULS_ERROR;
+
+  return ULS_OK;
+}
+
+usrp_load_status_t
+usrp_load_firmware (struct usb_dev_handle *udh,
+		    const char *filename,
+		    bool force)
+{
+  return usrp_conditionally_load_something (udh, filename, force,
+					    FIRMWARE_HASH_SLOT,
+					    _usrp_load_firmware);
+}
+
+usrp_load_status_t
+usrp_load_fpga (struct usb_dev_handle *udh,
+		const char *filename,
+		bool force)
+{
+  return usrp_conditionally_load_something (udh, filename, force,
+					    FPGA_HASH_SLOT,
+					    _usrp_load_fpga);
+}
+
+static usb_dev_handle *
+open_nth_cmd_interface (int nth)
+{
+  struct usb_device *udev = usrp_find_device (nth);
+  if (udev == 0){
+    fprintf (stderr, "usrp: failed to find usrp[%d]\n", nth);
+    return 0;
+  }
+
+  struct usb_dev_handle *udh;
+
+  udh = usrp_open_cmd_interface (udev);
+  if (udh == 0){
+    // FIXME this could be because somebody else has it open.
+    // We should delay and retry...
+    fprintf (stderr, "open_nth_cmd_interface: open_cmd_interface failed\n");
+    usb_strerror ();
+    return 0;
+  }
+
+  return udh;
+ }
+
+static bool
+our_nanosleep (const struct timespec *delay)
+{
+  struct timespec	new_delay = *delay;
+  struct timespec	remainder;
+
+  while (1){
+    int r = nanosleep (&new_delay, &remainder);
+    if (r == 0)
+      return true;
+    if (errno == EINTR)
+      new_delay = remainder;
+    else {
+      perror ("nanosleep");
+      return false;
+    }
+  }
+}
+
+static bool
+mdelay (int millisecs)
+{
+  struct timespec	ts;
+  ts.tv_sec = millisecs / 1000;
+  ts.tv_nsec = (millisecs - (1000 * ts.tv_sec)) * 1000000;
+  return our_nanosleep (&ts);
+}
+
+usrp_load_status_t
+usrp_load_firmware_nth (int nth, const char *filename, bool force){
+  struct usb_dev_handle *udh = open_nth_cmd_interface (nth);
+  if (udh == 0)
+    return ULS_ERROR;
+
+  usrp_load_status_t s = usrp_load_firmware (udh, filename, force);
+  usrp_close_interface (udh);
+
+  switch (s){
+
+  case ULS_ALREADY_LOADED:		// nothing changed...
+    return ULS_ALREADY_LOADED;
+    break;
+
+  case ULS_OK:
+    // we loaded firmware successfully.
+
+    // It's highly likely that the board will renumerate (simulate a
+    // disconnect/reconnect sequence), invalidating our current
+    // handle.
+
+    // FIXME.  Turn this into a loop that rescans until we refind ourselves
+    
+    struct timespec	t;	// delay for 1 second
+    t.tv_sec = 2;
+    t.tv_nsec = 0;
+    our_nanosleep (&t);
+
+    usb_find_busses ();		// rescan busses and devices
+    usb_find_devices ();
+
+    return ULS_OK;
+
+  default:
+  case ULS_ERROR:		// some kind of problem
+    return ULS_ERROR;
+  }
+}
+
+static void
+load_status_msg (usrp_load_status_t s, const char *type, const char *filename)
+{
+  char *e = getenv("USRP_VERBOSE");
+  bool verbose = e != 0;
+  
+  switch (s){
+  case ULS_ERROR:
+    fprintf (stderr, "usrp: failed to load %s %s.\n", type, filename);
+    break;
+    
+  case ULS_ALREADY_LOADED:
+    if (verbose)
+      fprintf (stderr, "usrp: %s %s already loaded.\n", type, filename);
+    break;
+
+  case ULS_OK:
+    if (verbose)
+      fprintf (stderr, "usrp: %s %s loaded successfully.\n", type, filename);
+    break;
+  }
+}
+
+bool
+usrp_load_standard_bits (int nth, bool force,
+			 const std::string fpga_filename,
+			 const std::string firmware_filename)
+{
+  usrp_load_status_t 	s;
+  const char		*filename;
+  const char		*proto_filename;
+  int hw_rev;
+
+  // first, figure out what hardware rev we're dealing with
+  {
+    struct usb_device *udev = usrp_find_device (nth);
+    if (udev == 0){
+      fprintf (stderr, "usrp: failed to find usrp[%d]\n", nth);
+      return false;
+    }
+    hw_rev = usrp_hw_rev (udev);
+  }
+
+  // start by loading the firmware
+
+  proto_filename = get_proto_filename(firmware_filename, "USRP_FIRMWARE",
+				      default_firmware_filename);
+  filename = find_file(proto_filename, hw_rev);
+  if (filename == 0){
+    fprintf (stderr, "Can't find firmware: %s\n", proto_filename);
+    return false;
+  }
+
+  s = usrp_load_firmware_nth (nth, filename, force);
+  load_status_msg (s, "firmware", filename);
+
+  if (s == ULS_ERROR)
+    return false;
+
+  // if we actually loaded firmware, we must reload fpga ...
+  if (s == ULS_OK)
+    force = true;
+
+  // now move on to the fpga configuration bitstream
+
+  proto_filename = get_proto_filename(fpga_filename, "USRP_FPGA",
+				      default_fpga_filename);
+  filename = find_file (proto_filename, hw_rev);
+  if (filename == 0){
+    fprintf (stderr, "Can't find fpga bitstream: %s\n", proto_filename);
+    return false;
+  }
+
+  struct usb_dev_handle *udh = open_nth_cmd_interface (nth);
+  if (udh == 0)
+    return false;
+  
+  s = usrp_load_fpga (udh, filename, force);
+  usrp_close_interface (udh);
+  load_status_msg (s, "fpga bitstream", filename);
+
+  if (s == ULS_ERROR)
+    return false;
+
+  return true;
+}
+
+bool
+_usrp_get_status (struct usb_dev_handle *udh, int which, bool *trouble)
+{
+  unsigned char	status;
+  *trouble = true;
+  
+  if (write_cmd (udh, VRQ_GET_STATUS, 0, which,
+		 &status, sizeof (status)) != sizeof (status))
+    return false;
+
+  *trouble = status;
+  return true;
+}
+
+bool
+usrp_check_rx_overrun (struct usb_dev_handle *udh, bool *overrun_p)
+{
+  return _usrp_get_status (udh, GS_RX_OVERRUN, overrun_p);
+}
+
+bool
+usrp_check_tx_underrun (struct usb_dev_handle *udh, bool *underrun_p)
+{
+  return _usrp_get_status (udh, GS_TX_UNDERRUN, underrun_p);
+}
+
+
+bool
+usrp_i2c_write (struct usb_dev_handle *udh, int i2c_addr,
+		const void *buf, int len)
+{
+  if (len < 1 || len > MAX_EP0_PKTSIZE)
+    return false;
+
+  return write_cmd (udh, VRQ_I2C_WRITE, i2c_addr, 0,
+		    (unsigned char *) buf, len) == len;
+}
+
+
+bool
+usrp_i2c_read (struct usb_dev_handle *udh, int i2c_addr,
+	       void *buf, int len)
+{
+  if (len < 1 || len > MAX_EP0_PKTSIZE)
+    return false;
+
+  return write_cmd (udh, VRQ_I2C_READ, i2c_addr, 0,
+		    (unsigned char *) buf, len) == len;
+}
+
+bool
+usrp_spi_write (struct usb_dev_handle *udh,
+		int optional_header, int enables, int format,
+		const void *buf, int len)
+{
+  if (len < 0 || len > MAX_EP0_PKTSIZE)
+    return false;
+
+  return write_cmd (udh, VRQ_SPI_WRITE,
+		    optional_header,
+		    ((enables & 0xff) << 8) | (format & 0xff),
+		    (unsigned char *) buf, len) == len;
+}
+
+
+bool
+usrp_spi_read (struct usb_dev_handle *udh,
+	       int optional_header, int enables, int format,
+	       void *buf, int len)
+{
+  if (len < 0 || len > MAX_EP0_PKTSIZE)
+    return false;
+
+  return write_cmd (udh, VRQ_SPI_READ,
+		    optional_header,
+		    ((enables & 0xff) << 8) | (format & 0xff),
+		    (unsigned char *) buf, len) == len;
+}
+
+bool
+usrp_9862_write (struct usb_dev_handle *udh, int which_codec,
+		 int regno, int value)
+{
+  if (0)
+    fprintf (stderr, "usrp_9862_write which = %d, reg = %2d, val = %3d (0x%02x)\n",
+	     which_codec, regno, value, value);
+
+  unsigned char buf[1];
+
+  buf[0] = value;
+  
+  return usrp_spi_write (udh, 0x00 | (regno & 0x3f),
+			 which_codec == 0 ? SPI_ENABLE_CODEC_A : SPI_ENABLE_CODEC_B,
+			 SPI_FMT_MSB | SPI_FMT_HDR_1,
+			 buf, 1);
+}
+
+bool
+usrp_9862_read (struct usb_dev_handle *udh, int which_codec,
+		int regno, unsigned char *value)
+{
+  return usrp_spi_read (udh, 0x80 | (regno & 0x3f),
+			which_codec == 0 ? SPI_ENABLE_CODEC_A : SPI_ENABLE_CODEC_B,
+			SPI_FMT_MSB | SPI_FMT_HDR_1,
+			value, 1);
+}
+
+bool
+usrp_9862_write_many (struct usb_dev_handle *udh,
+		      int which_codec,
+		      const unsigned char *buf,
+		      int len)
+{
+  if (len & 0x1)
+    return false;		// must be even
+
+  bool result = true;
+
+  while (len > 0){
+    result &= usrp_9862_write (udh, which_codec, buf[0], buf[1]);
+    len -= 2;
+    buf += 2;
+  }
+
+  return result;
+}
+
+
+bool
+usrp_9862_write_many_all (struct usb_dev_handle *udh,
+			   const unsigned char *buf, int len)
+{
+  // FIXME handle 2/2 and 4/4 versions
+
+  bool result;
+  result  = usrp_9862_write_many (udh, 0, buf, len);
+  result &= usrp_9862_write_many (udh, 1, buf, len);
+  return result;
+}
+
+static void
+power_down_9862s (struct usb_dev_handle *udh)
+{
+  static const unsigned char regs[] = {
+    REG_RX_PWR_DN,	0x01,			// everything
+    REG_TX_PWR_DN,	0x0f,			// pwr dn digital and analog_both
+    REG_TX_MODULATOR,	0x00			// coarse & fine modulators disabled
+  };
+
+  switch (usrp_hw_rev (dev_handle_to_dev (udh))){
+  case 0:
+    break;
+
+  default:
+    usrp_9862_write_many_all (udh, regs, sizeof (regs));
+    break;
+  }
+}
+
+
+
+static const int EEPROM_PAGESIZE = 16;
+
+bool
+usrp_eeprom_write (struct usb_dev_handle *udh, int i2c_addr,
+		   int eeprom_offset, const void *buf, int len)
+{
+  unsigned char cmd[2];
+  const unsigned char *p = (unsigned char *) buf;
+  
+  // The simplest thing that could possibly work:
+  //   all writes are single byte writes.
+  //
+  // We could speed this up using the page write feature,
+  // but we write so infrequently, why bother...
+
+  while (len-- > 0){
+    cmd[0] = eeprom_offset++;
+    cmd[1] = *p++;
+    bool r = usrp_i2c_write (udh, i2c_addr, cmd, sizeof (cmd));
+    mdelay (10);		// delay 10ms worst case write time
+    if (!r)
+      return false;
+  }
+  
+  return true;
+}
+
+bool
+usrp_eeprom_read (struct usb_dev_handle *udh, int i2c_addr,
+		  int eeprom_offset, void *buf, int len)
+{
+  unsigned char *p = (unsigned char *) buf;
+
+  // We setup a random read by first doing a "zero byte write".
+  // Writes carry an address.  Reads use an implicit address.
+
+  unsigned char cmd[1];
+  cmd[0] = eeprom_offset;
+  if (!usrp_i2c_write (udh, i2c_addr, cmd, sizeof (cmd)))
+    return false;
+
+  while (len > 0){
+    int n = std::min (len, MAX_EP0_PKTSIZE);
+    if (!usrp_i2c_read (udh, i2c_addr, p, n))
+      return false;
+    len -= n;
+    p += n;
+  }
+  return true;
+}
+ 
+// ----------------------------------------------------------------
+
+static bool
+slot_to_codec (int slot, int *which_codec)
+{
+  *which_codec = 0;
+  
+  switch (slot){
+  case SLOT_TX_A:
+  case SLOT_RX_A:
+    *which_codec = 0;
+    break;
+
+  case SLOT_TX_B:
+  case SLOT_RX_B:
+    *which_codec = 1;
+    break;
+
+  default:
+    fprintf (stderr, "usrp_prims:slot_to_codec: invalid slot = %d\n", slot);
+    return false;
+  }
+  return true;
+}
+
+static bool
+tx_slot_p (int slot)
+{
+  switch (slot){
+  case SLOT_TX_A:
+  case SLOT_TX_B:
+    return true;
+
+  default:
+    return false;
+  }
+}
+
+bool
+usrp_write_aux_dac (struct usb_dev_handle *udh, int slot,
+		    int which_dac, int value)
+{
+  int which_codec;
+  
+  if (!slot_to_codec (slot, &which_codec))
+    return false;
+
+  if (!(0 <= which_dac && which_dac < 4)){
+    fprintf (stderr, "usrp_write_aux_dac: invalid dac = %d\n", which_dac);
+    return false;
+  }
+
+  value &= 0x0fff;	// mask to 12-bits
+  
+  if (which_dac == 3){
+    // dac 3 is really 12-bits.  Use value as is.
+    bool r = true;
+    r &= usrp_9862_write (udh, which_codec, 43, (value >> 4));       // most sig
+    r &= usrp_9862_write (udh, which_codec, 42, (value & 0xf) << 4); // least sig
+    return r;
+  }
+  else {
+    // dac 0, 1, and 2 are really 8 bits.  
+    value = value >> 4;		// shift value appropriately
+    return usrp_9862_write (udh, which_codec, 36 + which_dac, value);
+  }
+}
+
+
+bool
+usrp_read_aux_adc (struct usb_dev_handle *udh, int slot,
+		   int which_adc, int *value)
+{
+  *value = 0;
+  int	which_codec;
+
+  if (!slot_to_codec (slot, &which_codec))
+    return false;
+
+  if (!(0 <= which_codec && which_codec < 2)){
+    fprintf (stderr, "usrp_read_aux_adc: invalid adc = %d\n", which_adc);
+    return false;
+  }
+
+  unsigned char aux_adc_control =
+    AUX_ADC_CTRL_REFSEL_A		// on chip reference
+    | AUX_ADC_CTRL_REFSEL_B;		// on chip reference
+
+  int	rd_reg = 26;	// base address of two regs to read for result
+  
+  // program the ADC mux bits
+  if (tx_slot_p (slot))
+    aux_adc_control |= AUX_ADC_CTRL_SELECT_A2 | AUX_ADC_CTRL_SELECT_B2;
+  else {
+    rd_reg += 2;
+    aux_adc_control |= AUX_ADC_CTRL_SELECT_A1 | AUX_ADC_CTRL_SELECT_B1;
+  }
+  
+  // I'm not sure if we can set the mux and issue a start conversion
+  // in the same cycle, so let's do them one at a time.
+
+  usrp_9862_write (udh, which_codec, 34, aux_adc_control);
+
+  if (which_adc == 0)
+    aux_adc_control |= AUX_ADC_CTRL_START_A;
+  else {
+    rd_reg += 4;
+    aux_adc_control |= AUX_ADC_CTRL_START_B;
+  }
+
+  // start the conversion
+  usrp_9862_write (udh, which_codec, 34, aux_adc_control);
+
+  // read the 10-bit result back
+  unsigned char v_lo = 0;
+  unsigned char v_hi = 0;
+  bool r = usrp_9862_read (udh, which_codec, rd_reg, &v_lo);
+  r &= usrp_9862_read (udh, which_codec, rd_reg + 1, &v_hi);
+
+  if (r)
+    *value = ((v_hi << 2) | ((v_lo >> 6) & 0x3)) << 2;	// format as 12-bit
+  
+  return r;
+}
+
+// ----------------------------------------------------------------
+
+static int slot_to_i2c_addr (int slot)
+{
+  switch (slot){
+  case SLOT_TX_A:	return I2C_ADDR_TX_A;
+  case SLOT_RX_A:	return I2C_ADDR_RX_A;
+  case SLOT_TX_B:	return I2C_ADDR_TX_B;
+  case SLOT_RX_B:	return I2C_ADDR_RX_B;
+  default:		return -1;
+  }
+}
+
+static void
+set_chksum (unsigned char *buf)
+{
+  int sum = 0;
+  unsigned int i;
+  for (i = 0; i < DB_EEPROM_CLEN - 1; i++)
+    sum += buf[i];
+  buf[i] = -sum;
+}
+
+static usrp_dbeeprom_status_t
+read_dboard_eeprom (struct usb_dev_handle *udh,
+		    int slot_id, unsigned char *buf)
+{
+  int i2c_addr = slot_to_i2c_addr (slot_id);
+  if (i2c_addr == -1)
+    return UDBE_BAD_SLOT;
+
+  if (!usrp_eeprom_read (udh, i2c_addr, 0, buf, DB_EEPROM_CLEN))
+    return UDBE_NO_EEPROM;
+
+  if (buf[DB_EEPROM_MAGIC] != DB_EEPROM_MAGIC_VALUE)
+    return UDBE_INVALID_EEPROM;
+
+  int sum = 0;
+  for (unsigned int i = 0; i < DB_EEPROM_CLEN; i++)
+    sum += buf[i];
+
+  if ((sum & 0xff) != 0)
+    return UDBE_INVALID_EEPROM;
+
+  return UDBE_OK;
+}
+
+usrp_dbeeprom_status_t
+usrp_read_dboard_eeprom (struct usb_dev_handle *udh,
+			 int slot_id, usrp_dboard_eeprom *eeprom)
+{
+  unsigned char buf[DB_EEPROM_CLEN];
+
+  memset (eeprom, 0, sizeof (*eeprom));
+
+  usrp_dbeeprom_status_t s = read_dboard_eeprom (udh, slot_id, buf);
+  if (s != UDBE_OK)
+    return s;
+
+  eeprom->id = (buf[DB_EEPROM_ID_MSB] << 8) | buf[DB_EEPROM_ID_LSB];
+  eeprom->oe = (buf[DB_EEPROM_OE_MSB] << 8) | buf[DB_EEPROM_OE_LSB];
+  eeprom->offset[0] = (buf[DB_EEPROM_OFFSET_0_MSB] << 8) | buf[DB_EEPROM_OFFSET_0_LSB];
+  eeprom->offset[1] = (buf[DB_EEPROM_OFFSET_1_MSB] << 8) | buf[DB_EEPROM_OFFSET_1_LSB];
+
+  return UDBE_OK;
+}
+
+bool
+usrp_write_dboard_offsets (struct usb_dev_handle *udh, int slot_id,
+			   short offset0, short offset1)
+{
+  unsigned char buf[DB_EEPROM_CLEN];
+
+  usrp_dbeeprom_status_t s = read_dboard_eeprom (udh, slot_id, buf);
+  if (s != UDBE_OK)
+    return false;
+
+  buf[DB_EEPROM_OFFSET_0_LSB] = (offset0 >> 0) & 0xff;
+  buf[DB_EEPROM_OFFSET_0_MSB] = (offset0 >> 8) & 0xff;
+  buf[DB_EEPROM_OFFSET_1_LSB] = (offset1 >> 0) & 0xff;
+  buf[DB_EEPROM_OFFSET_1_MSB] = (offset1 >> 8) & 0xff;
+  set_chksum (buf);
+
+  return usrp_eeprom_write (udh, slot_to_i2c_addr (slot_id),
+			    0, buf, sizeof (buf));
+}
+
+std::string
+usrp_serial_number(struct usb_dev_handle *udh)
+{
+  unsigned char iserial = usb_device(udh)->descriptor.iSerialNumber;
+  if (iserial == 0)
+    return "";
+
+  char buf[1024];
+  if (usb_get_string_simple(udh, iserial, buf, sizeof(buf)) < 0)
+    return "";
+
+  return buf;
+}