Merge branch 'next' into usrp_e_next

Conflicts:
	host/examples/CMakeLists.txt

9 files changed, 120 insertions, 146 deletions

diff --git a/host/examples/CMakeLists.txt b/host/examples/CMakeLists.txt
index 3203cffc0..ce2ca9640 100644
--- a/host/examples/CMakeLists.txt
+++ b/host/examples/CMakeLists.txt
@@ -16,46 +16,27 @@
 #
 
 ########################################################################
-ADD_EXECUTABLE(benchmark_rx_rate benchmark_rx_rate.cpp)
-TARGET_LINK_LIBRARIES(benchmark_rx_rate uhd)
-
-ADD_EXECUTABLE(rx_timed_samples rx_timed_samples.cpp)
-TARGET_LINK_LIBRARIES(rx_timed_samples uhd)
-
-ADD_EXECUTABLE(rx_to_file rx_to_file.cpp)
-TARGET_LINK_LIBRARIES(rx_to_file uhd)
-
-ADD_EXECUTABLE(rx_to_udp rx_to_udp.cpp)
-TARGET_LINK_LIBRARIES(rx_to_udp uhd)
-
-ADD_EXECUTABLE(test_async_messages test_async_messages.cpp)
-TARGET_LINK_LIBRARIES(test_async_messages uhd)
-
-ADD_EXECUTABLE(test_pps_input test_pps_input.cpp)
-TARGET_LINK_LIBRARIES(test_pps_input uhd)
-
-ADD_EXECUTABLE(tx_timed_samples tx_timed_samples.cpp)
-TARGET_LINK_LIBRARIES(tx_timed_samples uhd)
-
-ADD_EXECUTABLE(tx_from_file tx_from_file.cpp)
-TARGET_LINK_LIBRARIES(tx_from_file uhd)
-
-ADD_EXECUTABLE(tx_waveforms tx_waveforms.cpp)
-TARGET_LINK_LIBRARIES(tx_waveforms uhd)
-
-INSTALL(TARGETS
-    benchmark_rx_rate
-    rx_timed_samples
-    test_async_messages
-    test_pps_input
-    tx_timed_samples
-    tx_from_file
-    rx_to_file
-    rx_to_udp
-    tx_waveforms
-    RUNTIME DESTINATION ${PKG_DATA_DIR}/examples
+# example applications
+########################################################################
+SET(example_sources
+    benchmark_rx_rate.cpp
+    rx_samples_to_file.cpp
+    rx_samples_to_udp.cpp
+    rx_timed_samples.cpp
+    test_async_messages.cpp
+    test_pps_input.cpp
+    tx_timed_samples.cpp
+    tx_waveforms.cpp
 )
 
+#for each source: build an executable and install
+FOREACH(example_source ${example_sources})
+    GET_FILENAME_COMPONENT(example_name ${example_source} NAME_WE)
+    ADD_EXECUTABLE(${example_name} ${example_source})
+    TARGET_LINK_LIBRARIES(${example_name} uhd)
+    INSTALL(TARGETS ${example_name} RUNTIME DESTINATION ${PKG_DATA_DIR}/examples)
+ENDFOREACH(example_source)
+
 ########################################################################
 # ASCII Art DFT - requires curses, so this part is optional
 ########################################################################
diff --git a/host/examples/ascii_art_dft.hpp b/host/examples/ascii_art_dft.hpp
index 92fb77596..ee2267c2d 100644
--- a/host/examples/ascii_art_dft.hpp
+++ b/host/examples/ascii_art_dft.hpp
@@ -28,7 +28,7 @@ namespace acsii_art_dft{
     );
 
     /*!
-     * Convert a DFT to a printable ascii plot.
+     * Convert a DFT to a piroundable ascii plot.
      * \param dft the log power dft bins
      * \param width the frame width in characters
      * \param height the frame height in characters
diff --git a/host/examples/rx_to_file.cpp b/host/examples/rx_samples_to_file.cpp
index f08f7cee3..c80d2a6de 100644
--- a/host/examples/rx_to_file.cpp
+++ b/host/examples/rx_samples_to_file.cpp
@@ -20,32 +20,32 @@
 #include <uhd/usrp/single_usrp.hpp>
 #include <boost/program_options.hpp>
 #include <boost/format.hpp>
+#include <boost/thread.hpp>
 #include <iostream>
 #include <fstream>
 #include <complex>
 
 namespace po = boost::program_options;
 
-
 int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::set_thread_priority_safe();
 
     //variables to be set by po
-    std::string args;
-    time_t seconds_in_future;
+    std::string args, file;
     size_t total_num_samps;
-    double rx_rate, freq;
+    double rate, freq;
+    float gain;
 
     //setup the program options
     po::options_description desc("Allowed options");
     desc.add_options()
         ("help", "help message")
         ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args")
-        ("secs", po::value<time_t>(&seconds_in_future)->default_value(3), "number of seconds in the future to receive")
+        ("file", po::value<std::string>(&file)->default_value("out.16sc.dat"), "name of the file to write binary samples to")
         ("nsamps", po::value<size_t>(&total_num_samps)->default_value(1000), "total number of samples to receive")
-        ("rxrate", po::value<double>(&rx_rate)->default_value(100e6/16), "rate of incoming samples")
+        ("rate", po::value<double>(&rate)->default_value(100e6/16), "rate of incoming samples")
         ("freq", po::value<double>(&freq)->default_value(0), "rf center frequency in Hz")
-        ("dilv", "specify to disable inner-loop verbose")
+        ("gain", po::value<float>(&gain)->default_value(0), "gain for the RF chain")
     ;
     po::variables_map vm;
     po::store(po::parse_command_line(argc, argv, desc), vm);
@@ -57,8 +57,6 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         return ~0;
     }
 
-    bool verbose = vm.count("dilv") == 0;
-
     //create a usrp device
     std::cout << std::endl;
     std::cout << boost::format("Creating the usrp device with: %s...") % args << std::endl;
@@ -66,37 +64,35 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::device::sptr dev = sdev->get_device();
     std::cout << boost::format("Using Device: %s") % sdev->get_pp_string() << std::endl;
 
-    //set properties on the device
-    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rx_rate/1e6) << std::endl;
-    sdev->set_rx_rate(rx_rate);
-    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl;
-    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
+    //set the rx sample rate
+    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rate/1e6) << std::endl;
+    sdev->set_rx_rate(rate);
+    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl << std::endl;
+
+    //set the rx center frequency
+    std::cout << boost::format("Setting RX Freq: %f Mhz...") % (freq/1e6) << std::endl;
     sdev->set_rx_freq(freq);
-    sdev->set_time_now(uhd::time_spec_t(0.0));
+    std::cout << boost::format("Actual RX Freq: %f Mhz...") % (sdev->get_rx_freq()/1e6) << std::endl << std::endl;
 
-    uhd::gain_range_t rx_gain = sdev->get_rx_gain_range();
-    std::cout << "Setting RX Gain to: " << rx_gain.max << std::endl;
-    sdev->set_rx_gain(rx_gain.max);
+    //set the rx rf gain
+    std::cout << boost::format("Setting RX Gain: %f dB...") % gain << std::endl;
+    sdev->set_rx_gain(gain);
+    std::cout << boost::format("Actual RX Gain: %f dB...") % sdev->get_rx_gain() << std::endl << std::endl;
 
-    sleep(1);
+    boost::this_thread::sleep(boost::posix_time::seconds(1)); //allow for some setup time
     std::cout << "LO Locked = " << sdev->get_rx_lo_locked() << std::endl;
 
     //setup streaming
-    std::cout << std::endl;
-    std::cout << boost::format(
-        "Begin streaming %u samples, %d seconds in the future..."
-    ) % total_num_samps % seconds_in_future << std::endl;
     uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
     stream_cmd.num_samps = total_num_samps;
-    stream_cmd.stream_now = false;
-    stream_cmd.time_spec = uhd::time_spec_t(seconds_in_future);
+    stream_cmd.stream_now = true;
     sdev->issue_stream_cmd(stream_cmd);
 
     //loop until total number of samples reached
     size_t num_acc_samps = 0; //number of accumulated samples
     uhd::rx_metadata_t md;
     std::vector<std::complex<short> > buff(dev->get_max_recv_samps_per_packet());
-    std::ofstream outfile("out.dat", std::ofstream::binary);
+    std::ofstream outfile(file.c_str(), std::ofstream::binary);
 
     while(num_acc_samps < total_num_samps){
         size_t num_rx_samps = dev->recv(
@@ -124,11 +120,8 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
             goto done_loop;
         }
 
-	outfile.write((const char*)&buff[0], num_rx_samps * sizeof(std::complex<short>));
-
-        if(verbose) std::cout << boost::format(
-            "Got packet: %u samples, %u full secs, %f frac secs"
-        ) % num_rx_samps % md.time_spec.get_full_secs() % md.time_spec.get_frac_secs() << std::endl;
+        //write complex short integer samples to the binary file
+        outfile.write((const char*)&buff[0], num_rx_samps * sizeof(std::complex<short>));
 
         num_acc_samps += num_rx_samps;
     } done_loop:
diff --git a/host/examples/rx_to_udp.cpp b/host/examples/rx_samples_to_udp.cpp
index c8b3d506b..488c95494 100644
--- a/host/examples/rx_to_udp.cpp
+++ b/host/examples/rx_samples_to_udp.cpp
@@ -18,42 +18,36 @@
 #include <uhd/utils/thread_priority.hpp>
 #include <uhd/utils/safe_main.hpp>
 #include <uhd/usrp/single_usrp.hpp>
+#include <uhd/transport/udp_simple.hpp>
 #include <boost/program_options.hpp>
 #include <boost/format.hpp>
+#include <boost/thread.hpp>
 #include <iostream>
-#include <fstream>
 #include <complex>
 
-#include "sys/types.h"
-#include "sys/socket.h"
-#include "arpa/inet.h"
-
 namespace po = boost::program_options;
 
-
 int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::set_thread_priority_safe();
 
     //variables to be set by po
     std::string args;
-    time_t seconds_in_future;
     size_t total_num_samps;
-    double rx_rate, freq;
-    short srv_port;
-    std::string srv_ip;
+    double rate, freq;
+    float gain;
+    std::string addr, port;
 
     //setup the program options
     po::options_description desc("Allowed options");
     desc.add_options()
         ("help", "help message")
         ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args")
-        ("secs", po::value<time_t>(&seconds_in_future)->default_value(3), "number of seconds in the future to receive")
         ("nsamps", po::value<size_t>(&total_num_samps)->default_value(1000), "total number of samples to receive")
-        ("rxrate", po::value<double>(&rx_rate)->default_value(100e6/16), "rate of incoming samples")
+        ("rate", po::value<double>(&rate)->default_value(100e6/16), "rate of incoming samples")
         ("freq", po::value<double>(&freq)->default_value(0), "rf center frequency in Hz")
-        ("port", po::value<short>(&srv_port)->default_value(7124), "server port")
-        ("ip", po::value<std::string>(&srv_ip)->default_value("192.168.1.10"), "server ip")
-        ("dilv", "specify to disable inner-loop verbose")
+        ("gain", po::value<float>(&gain)->default_value(0), "gain for the RF chain")
+        ("port", po::value<std::string>(&port)->default_value("7124"), "server udp port")
+        ("addr", po::value<std::string>(&addr)->default_value("192.168.1.10"), "resolvable server address")
     ;
     po::variables_map vm;
     po::store(po::parse_command_line(argc, argv, desc), vm);
@@ -65,8 +59,6 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         return ~0;
     }
 
-    bool verbose = vm.count("dilv") == 0;
-
     //create a usrp device
     std::cout << std::endl;
     std::cout << boost::format("Creating the usrp device with: %s...") % args << std::endl;
@@ -74,52 +66,35 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::device::sptr dev = sdev->get_device();
     std::cout << boost::format("Using Device: %s") % sdev->get_pp_string() << std::endl;
 
-    //set properties on the device
-    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rx_rate/1e6) << std::endl;
-    sdev->set_rx_rate(rx_rate);
-    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl;
-    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
+    //set the rx sample rate
+    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rate/1e6) << std::endl;
+    sdev->set_rx_rate(rate);
+    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl << std::endl;
+
+    //set the rx center frequency
+    std::cout << boost::format("Setting RX Freq: %f Mhz...") % (freq/1e6) << std::endl;
     sdev->set_rx_freq(freq);
-    sdev->set_time_now(uhd::time_spec_t(0.0));
+    std::cout << boost::format("Actual RX Freq: %f Mhz...") % (sdev->get_rx_freq()/1e6) << std::endl << std::endl;
 
-    uhd::gain_range_t rx_gain = sdev->get_rx_gain_range();
-    std::cout << "Setting RX Gain to: " << rx_gain.max << std::endl;
-    sdev->set_rx_gain(rx_gain.max);
+    //set the rx rf gain
+    std::cout << boost::format("Setting RX Gain: %f dB...") % gain << std::endl;
+    sdev->set_rx_gain(gain);
+    std::cout << boost::format("Actual RX Gain: %f dB...") % sdev->get_rx_gain() << std::endl << std::endl;
 
-    sleep(1);
+    boost::this_thread::sleep(boost::posix_time::seconds(1)); //allow for some setup time
     std::cout << "LO Locked = " << sdev->get_rx_lo_locked() << std::endl;
 
     //setup streaming
-    std::cout << std::endl;
-    std::cout << boost::format(
-        "Begin streaming %u samples, %d seconds in the future..."
-    ) % total_num_samps % seconds_in_future << std::endl;
     uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
     stream_cmd.num_samps = total_num_samps;
-    stream_cmd.stream_now = false;
-    stream_cmd.time_spec = uhd::time_spec_t(seconds_in_future);
+    stream_cmd.stream_now = true;
     sdev->issue_stream_cmd(stream_cmd);
 
     //loop until total number of samples reached
     size_t num_acc_samps = 0; //number of accumulated samples
     uhd::rx_metadata_t md;
-    std::vector<std::complex<float> > buff(368);
-    std::ofstream outfile("out.dat", std::ofstream::binary);
-
-    int s;
-    struct sockaddr_in si_other;
-    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
-	std::cout << "Failid to open socket." << std::endl;
-    	return -1;
-    }	
-
-    memset((char *) &si_other, 0, sizeof(si_other));
-    si_other.sin_family = AF_INET;
-    si_other.sin_port = htons(srv_port);
-    if (inet_aton(srv_ip.c_str(), &si_other.sin_addr) == 0) {
-	    std::cout << "Bad inet addr: " << srv_ip << std::endl;
-	    return -1;
-    }
+    std::vector<std::complex<float> > buff(dev->get_max_recv_samps_per_packet());
+    uhd::transport::udp_simple::sptr udp_xport = uhd::transport::udp_simple::make_connected(addr, port);
 
     while(num_acc_samps < total_num_samps){
         size_t num_rx_samps = dev->recv(
@@ -147,19 +122,12 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
             goto done_loop;
         }
 
-//	outfile.write((const char*)&buff[0], num_rx_samps * sizeof(std::complex<short>));
-	if (sendto(s, (const char *)&buff[0], num_rx_samps * sizeof(std::complex<float>), 0 , (const sockaddr *)&si_other, sizeof(si_other)) == -1)
-		std::cout << "Sendto failed." << std::endl;
-
-        if(verbose) std::cout << boost::format(
-            "Got packet: %u samples, %u full secs, %f frac secs"
-        ) % num_rx_samps % md.time_spec.get_full_secs() % md.time_spec.get_frac_secs() << std::endl;
+        //send complex single precision floating point samples over udp
+        udp_xport->send(boost::asio::buffer(buff, num_rx_samps));
 
         num_acc_samps += num_rx_samps;
     } done_loop:
 
-    outfile.close();
-
     //finished
     std::cout << std::endl << "Done!" << std::endl << std::endl;
 
diff --git a/host/examples/rx_timed_samples.cpp b/host/examples/rx_timed_samples.cpp
index 441665900..8a810811f 100644
--- a/host/examples/rx_timed_samples.cpp
+++ b/host/examples/rx_timed_samples.cpp
@@ -32,7 +32,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     std::string args;
     time_t seconds_in_future;
     size_t total_num_samps;
-    double rx_rate, freq;
+    double rate, freq;
 
     //setup the program options
     po::options_description desc("Allowed options");
@@ -41,7 +41,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args")
         ("secs", po::value<time_t>(&seconds_in_future)->default_value(3), "number of seconds in the future to receive")
         ("nsamps", po::value<size_t>(&total_num_samps)->default_value(1000), "total number of samples to receive")
-        ("rxrate", po::value<double>(&rx_rate)->default_value(100e6/16), "rate of incoming samples")
+        ("rate", po::value<double>(&rate)->default_value(100e6/16), "rate of incoming samples")
         ("freq", po::value<double>(&freq)->default_value(0), "rf center frequency in Hz")
         ("dilv", "specify to disable inner-loop verbose")
     ;
@@ -64,12 +64,17 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::device::sptr dev = sdev->get_device();
     std::cout << boost::format("Using Device: %s") % sdev->get_pp_string() << std::endl;
 
-    //set properties on the device
-    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rx_rate/1e6) << std::endl;
-    sdev->set_rx_rate(rx_rate);
-    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl;
-    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
+    //set the rx sample rate
+    std::cout << boost::format("Setting RX Rate: %f Msps...") % (rate/1e6) << std::endl;
+    sdev->set_rx_rate(rate);
+    std::cout << boost::format("Actual RX Rate: %f Msps...") % (sdev->get_rx_rate()/1e6) << std::endl << std::endl;
+
+    //set the rx center frequency
+    std::cout << boost::format("Setting RX Freq: %f Mhz...") % (freq/1e6) << std::endl;
     sdev->set_rx_freq(freq);
+    std::cout << boost::format("Actual RX Freq: %f Mhz...") % (sdev->get_rx_freq()/1e6) << std::endl << std::endl;
+
+    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
     sdev->set_time_now(uhd::time_spec_t(0.0));
 
     //setup streaming
diff --git a/host/examples/tx_timed_samples.cpp b/host/examples/tx_timed_samples.cpp
index 863446682..799da37e0 100644
--- a/host/examples/tx_timed_samples.cpp
+++ b/host/examples/tx_timed_samples.cpp
@@ -33,7 +33,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     time_t seconds_in_future;
     size_t total_num_samps;
     size_t samps_per_packet;
-    double tx_rate, freq;
+    double rate, freq;
     float ampl;
 
     //setup the program options
@@ -44,7 +44,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         ("secs", po::value<time_t>(&seconds_in_future)->default_value(3), "number of seconds in the future to transmit")
         ("nsamps", po::value<size_t>(&total_num_samps)->default_value(1000), "total number of samples to transmit")
         ("spp", po::value<size_t>(&samps_per_packet)->default_value(1000), "number of samples per packet")
-        ("txrate", po::value<double>(&tx_rate)->default_value(100e6/16), "rate of outgoing samples")
+        ("rate", po::value<double>(&rate)->default_value(100e6/16), "rate of outgoing samples")
         ("freq", po::value<double>(&freq)->default_value(0), "rf center frequency in Hz")
         ("ampl", po::value<float>(&ampl)->default_value(float(0.3)), "amplitude of each sample")
         ("dilv", "specify to disable inner-loop verbose")
@@ -68,12 +68,17 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::device::sptr dev = sdev->get_device();
     std::cout << boost::format("Using Device: %s") % sdev->get_pp_string() << std::endl;
 
-    //set properties on the device
-    std::cout << boost::format("Setting TX Rate: %f Msps...") % (tx_rate/1e6) << std::endl;
-    sdev->set_tx_rate(tx_rate);
-    std::cout << boost::format("Actual TX Rate: %f Msps...") % (sdev->get_tx_rate()/1e6) << std::endl;
-    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
+    //set the tx sample rate
+    std::cout << boost::format("Setting TX Rate: %f Msps...") % (rate/1e6) << std::endl;
+    sdev->set_tx_rate(rate);
+    std::cout << boost::format("Actual TX Rate: %f Msps...") % (sdev->get_tx_rate()/1e6) << std::endl << std::endl;
+
+    //set the tx center frequency
+    std::cout << boost::format("Setting TX Freq: %f Mhz...") % (freq/1e6) << std::endl;
     sdev->set_tx_freq(freq);
+    std::cout << boost::format("Actual TX Freq: %f Mhz...") % (sdev->get_tx_freq()/1e6) << std::endl << std::endl;
+
+    std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
     sdev->set_time_now(uhd::time_spec_t(0.0));
 
     //allocate data to send
diff --git a/host/include/uhd/usrp/multi_usrp.hpp b/host/include/uhd/usrp/multi_usrp.hpp
index 5380d177d..98ba07fc0 100644
--- a/host/include/uhd/usrp/multi_usrp.hpp
+++ b/host/include/uhd/usrp/multi_usrp.hpp
@@ -145,6 +145,14 @@ public:
     virtual void set_time_unknown_pps(const time_spec_t &time_spec) = 0;
 
     /*!
+     * Are the times across all motherboards in this configuration synchronized?
+     * Checks that all time registers are approximately close but not exact,
+     * given that the RTT may varying for a control packet transaction.
+     * \return true when all motherboards time registers are in sync
+     */
+    virtual bool get_time_synchronized(void) = 0;
+
+    /*!
      * Issue a stream command to the usrp device.
      * This tells the usrp to send samples into the host.
      * See the documentation for stream_cmd_t for more info.
diff --git a/host/include/uhd/usrp/subdev_spec.hpp b/host/include/uhd/usrp/subdev_spec.hpp
index 5de3bb3b8..b189724c9 100644
--- a/host/include/uhd/usrp/subdev_spec.hpp
+++ b/host/include/uhd/usrp/subdev_spec.hpp
@@ -26,10 +26,10 @@
 namespace uhd{ namespace usrp{
 
     /*!
-     * A subdevice specification (daughterboard, subdevice) name pairing.
+     * A subdevice specification (daughterboard slot, subdevice) name pairing.
      */
     struct UHD_API subdev_spec_pair_t : boost::equality_comparable<subdev_spec_pair_t>{
-        //! The daughterboard name
+        //! The daughterboard slot name
         std::string db_name;
 
         //! The subdevice name
@@ -50,7 +50,7 @@ namespace uhd{ namespace usrp{
     UHD_API bool operator==(const subdev_spec_pair_t &, const subdev_spec_pair_t &);
 
     /*!
-     * A list of (daughterboard name, subdevice name) pairs:
+     * A list of (daughterboard slot name, subdevice name) pairs:
      *
      * A subdevice specification represents a list of subdevices on a motherboard.
      * The subdevices specified may span across multiple daughterboards;
@@ -62,6 +62,11 @@ namespace uhd{ namespace usrp{
      * The markup-string is a whitespace separated list of dboard:subdev pairs.
      * The first pair represents the subdevice for channel zero,
      * the second pair represents the subdevice for channel one, and so on.
+     *
+     * Special handling for empty conditions:
+     * - An empty subdevice specification means: select the first subdevice found in the configuration
+     * - An empty daughterboard name means: select the only daughterboard slot or error if multiple exist
+     * - An empty subdevice name means: select the only subdevice on that board or error if multiple exist
      */
     class UHD_API subdev_spec_t : public std::vector<subdev_spec_pair_t>{
     public:
diff --git a/host/lib/usrp/multi_usrp.cpp b/host/lib/usrp/multi_usrp.cpp
index 024a6152d..876f1a3fc 100644
--- a/host/lib/usrp/multi_usrp.cpp
+++ b/host/lib/usrp/multi_usrp.cpp
@@ -154,6 +154,15 @@ public:
         }
     }
 
+    bool get_time_synchronized(void){
+        for (size_t m = 1; m < get_num_mboards(); m++){
+            time_spec_t time_0 = _mboard(0)[MBOARD_PROP_TIME_NOW].as<time_spec_t>();
+            time_spec_t time_i = _mboard(m)[MBOARD_PROP_TIME_NOW].as<time_spec_t>();
+            if (time_i < time_0 or (time_i - time_0) > time_spec_t(0.01)) return false;
+        }
+        return true;
+    }
+
     void issue_stream_cmd(const stream_cmd_t &stream_cmd){
         for (size_t m = 0; m < get_num_mboards(); m++){
             _mboard(m)[MBOARD_PROP_STREAM_CMD] = stream_cmd;