examples: Revised frequency hopping example for best practices

1 files changed, 114 insertions, 126 deletions

diff --git a/host/examples/twinrx_freq_hopping.cpp b/host/examples/twinrx_freq_hopping.cpp
index 1fc0249ed..6d7018912 100644
--- a/host/examples/twinrx_freq_hopping.cpp
+++ b/host/examples/twinrx_freq_hopping.cpp
@@ -15,29 +15,25 @@
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 //
 
+// FFT conversion
+#include "ascii_art_dft.hpp"
+
 #include <uhd/utils/thread_priority.hpp>
 #include <uhd/utils/safe_main.hpp>
 #include <uhd/usrp/multi_usrp.hpp>
 
 #include <boost/program_options.hpp>
-#include <boost/format.hpp>
 #include <boost/thread.hpp>
 
 #include <fstream>
-#include <iostream>
-#include <complex>
-#include <utility>
-
-// FFT conversion
-#include "ascii_art_dft.hpp"
 
 /*
  * This example shows how to implement fast frequency hopping using an X-Series
  * motherboard and a TwinRX daughterboard.
  *
- * The TwinRX daughterboard is different than previous daughterboards in that it
- * has two RX channels and two LOs. Either channel can be set to use either LO,
- * allowing for the two channels to share an LO source.
+ * The TwinRX daughterboard is different than previous daughterboards in that it has two
+ * RX channels, each with a set of Local Oscillators (LOs). Either channel can be configured
+ * to use either LO set, allowing for the two channels to share an LO source.
  *
  * The TwinRX can be used like any other daughterboard, as the multi_usrp::set_rx_freq()
  * function will automatically calculate and set the two LO frequencies as needed.
@@ -48,7 +44,7 @@
  *
  * 1. Tune across the given frequency range, storing the calculated LO frequencies along
  *    the way.
- * 2. Use timed commands to tell the TwinRX to send samples to the host at given intervals.
+ * 2. Use timed commands to tell the TwinRX to receive bursts of samples at given intervals.
  * 3. For each frequency, tune the LOs for the inactive channel for the next frequency and
  *    receive at the current frequency.
  * 4. If applicable, send the next timed command for streaming.
@@ -57,12 +53,9 @@
 namespace pt = boost::posix_time;
 namespace po = boost::program_options;
 
-typedef std::pair<double, double> lo_freqs_t;
 typedef std::vector<std::complex<float> > recv_buff_t;
 typedef std::vector<recv_buff_t> recv_buffs_t;
 
-double pipeline_time;
-
 // Global objects
 static uhd::usrp::multi_usrp::sptr usrp;
 static uhd::rx_streamer::sptr rx_stream;
@@ -70,55 +63,47 @@ static recv_buffs_t buffs;
 static size_t recv_spb, spb;
 
 static std::vector<double> rf_freqs;
-static std::vector<lo_freqs_t> lo_freqs;
 
 static uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
-static uhd::time_spec_t pipeline_timespec;
-static size_t last_cmd_index;
 
-// Determine the active channel (hooked to antenna) and the slave channel
+double receive_interval;
+
+// Define the active channel (connected to antenna) and the unused channel
 size_t ACTIVE_CHAN = 0;
 size_t UNUSED_CHAN = 1;
 
-const std::string ALL_STAGES = "all";
-
 const int X300_COMMAND_FIFO_DEPTH = 16;
 
-static void twinrx_recv(size_t index) {
+
+// This is a helper function for receiving samples from the USRP
+static void twinrx_recv(recv_buff_t &buffer) {
+
     size_t num_acc_samps = 0;
     uhd::rx_metadata_t md;
 
-    while(num_acc_samps < spb) {
+    // Repeatedly retrieve samples until the entire acquisition is received
+    while (num_acc_samps < spb) {
         size_t num_to_recv = std::min<size_t>(recv_spb, (spb - num_acc_samps));
 
-        size_t num_recvd = rx_stream->recv(
-            &buffs[index][num_acc_samps],
-            num_to_recv, md, pipeline_time
-        );
+        // recv call will block until samples are ready or the call times out
+        size_t num_recvd = rx_stream->recv(&buffer[num_acc_samps], num_to_recv, md, receive_interval);
 
         if(md.error_code != uhd::rx_metadata_t::ERROR_CODE_NONE) {
-            std::cout << index << " " << md.strerror() << std::endl;
+            std::cout << md.strerror() << std::endl;
             break;
         }
-
         num_acc_samps += num_recvd;
     }
-
-    // Send the next stream_cmd
-    if(last_cmd_index < buffs.size()) {
-        stream_cmd.time_spec += pipeline_timespec;
-        rx_stream->issue_stream_cmd(stream_cmd);
-        ++last_cmd_index;
-    }
 }
 
+// Function to write the acquisition FFT to a binary file
 static void write_fft_to_file(const std::string &fft_path) {
-    std::cout << "Creating FFT (this may take a while)..." << std::flush;
+    std::cout << "Calculating FFTs (this may take a while)... " << std::flush;
     std::ofstream ofile(fft_path.c_str(), std::ios::binary);
     BOOST_FOREACH(const recv_buff_t &buff, buffs) {
-        std::vector<float> fft = acsii_art_dft::log_pwr_dft(&buff.front(), buff.size());
-        ofile.write((char*)&fft[0], (sizeof(float)*fft.size()));
-    }
+                    std::vector<float> fft = acsii_art_dft::log_pwr_dft(&buff.front(), buff.size());
+                    ofile.write((char*)&fft[0], (sizeof(float)*fft.size()));
+                }
     ofile.close();
     std::cout << "done." << std::endl;
 }
@@ -127,43 +112,43 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     uhd::set_thread_priority_safe();
 
     // Program options
-    std::string args, fft_path, subdev;
+    std::string args, fft_path, subdev, ant;
     double rate, gain;
     double start_freq, end_freq;
 
     // Set up the program options
     po::options_description desc("Allowed options");
     desc.add_options()
-    ("help", "Print this help message")
-    ("args", po::value<std::string>(&args)->default_value(""), "UHD device args")
-    ("subdev", po::value<std::string>(&subdev)->default_value("A:0 A:1"), "Subdevice specification")
-    ("start-freq", po::value<double>(&start_freq), "Start frequency (defaults to lowest valid frequency)")
-    ("end-freq", po::value<double>(&end_freq), "End frequency (defaults to highest valid frequency)")
-    ("pipeline-time", po::value<double>(&pipeline_time)->default_value(5e-3), "Time spent tuning and receiving")
-    ("rate", po::value<double>(&rate)->default_value(1e6), "Incoming sample rate")
-    ("gain", po::value<double>(&gain)->default_value(60), "RX gain")
-    ("spb", po::value<size_t>(&spb)->default_value(1024), "Samples per buffer")
-    ("fft-path", po::value<std::string>(&fft_path), "Output an FFT to this file (optional)")
-    ("repeat", "repeat loop until Ctrl-C is pressed")
-    ;
+            ("help", "Print this help message")
+            ("args", po::value<std::string>(&args)->default_value(""), "UHD device args")
+            ("subdev", po::value<std::string>(&subdev)->default_value("A:0 A:1"), "Subdevice specification")
+            ("ant", po::value<std::string>(&ant)->default_value("RX1"), "RX Antenna")
+            ("start-freq", po::value<double>(&start_freq), "Start frequency (defaults to lowest valid frequency)")
+            ("end-freq", po::value<double>(&end_freq), "End frequency (defaults to highest valid frequency)")
+            ("receive-interval", po::value<double>(&receive_interval)->default_value(5e-3), "Interval between scheduled receives")
+            ("rate", po::value<double>(&rate)->default_value(1e6), "Incoming sample rate")
+            ("gain", po::value<double>(&gain)->default_value(60), "RX gain")
+            ("spb", po::value<size_t>(&spb)->default_value(1024), "Samples per buffer")
+            ("fft-path", po::value<std::string>(&fft_path), "Output an FFT to this file (optional)")
+            ("repeat", "repeat sweep until Ctrl-C is pressed")
+            ;
     po::variables_map vm;
     po::store(po::parse_command_line(argc, argv, desc), vm);
     po::notify(vm);
 
     if(vm.count("help")) {
-        std::cout << "TwinRX Example - " << desc << std::endl;
+        std::cout << "TwinRX Frequency Hopping Example - " << desc << std::endl;
         return EXIT_SUCCESS;
     }
 
     // Create a USRP device
-    std::cout << std::endl;
-    std::cout << boost::format("Creating the USRP device with args: \"%s\"...") % args << std::endl;
+    std::cout << boost::format("\nCreating the USRP device with args: \"%s\"...\n") % args;
     usrp = uhd::usrp::multi_usrp::make(args);
 
-    // Make sure this is an X3xx with a TwinRX
+    // Make sure the USRP is an X3xx with a TwinRX
     uhd::dict<std::string, std::string> info = usrp->get_usrp_rx_info();
     if(info.get("mboard_id").find("X3") == std::string::npos) {
-        throw uhd::runtime_error("This example can only be used with an X-Series device.");
+        throw uhd::runtime_error("This example can only be used with an X-Series motherboard.");
     }
     if(info.get("rx_id").find("TwinRX") == std::string::npos) {
         throw uhd::runtime_error("This example can only be used with a TwinRX daughterboard.");
@@ -171,122 +156,125 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
 
     // Validate frequency range
     uhd::freq_range_t rx_freq_range = usrp->get_rx_freq_range();
-    if(!vm.count("start-freq")) {
+    if (!vm.count("start-freq")) {
         start_freq = rx_freq_range.start();
     }
-    if(!vm.count("end-freq")) {
+    if (!vm.count("end-freq")) {
         end_freq = rx_freq_range.stop();
     }
-    if(start_freq > end_freq) {
+    if (start_freq < rx_freq_range.start() or end_freq > rx_freq_range.stop()) {
+        throw uhd::runtime_error((boost::format("Start and stop frequencies must be between %d and %d MHz")
+                                            % ((rx_freq_range.start() / 1e6), (rx_freq_range.stop() / 1e6))).str());
+    }
+    if (start_freq > end_freq) {
         throw uhd::runtime_error("Start frequency must be less than end frequency.");
     }
-    if((end_freq - start_freq) > 0 and (end_freq - start_freq) < rate) {
+    if ((end_freq - start_freq) > 0 and (end_freq - start_freq) < rate) {
         throw uhd::runtime_error("The sample rate must be less than the range between the start and end frequencies.");
     }
 
     // Set TwinRX settings
-    usrp->set_rx_subdev_spec(uhd::usrp::subdev_spec_t(subdev));
-    usrp->set_rx_antenna("RX1", 0);
-    usrp->set_rx_antenna("RX2", 1);
-    
-    // Disable the LO for the unused channel
-    usrp->set_rx_lo_source("disabled", ALL_STAGES, UNUSED_CHAN);
+    usrp->set_rx_subdev_spec(subdev);
+
+    // Set the unused channel to not use any LOs. This allows the active channel to control them.
+    usrp->set_rx_lo_source("disabled", uhd::usrp::multi_usrp::ALL_LOS, UNUSED_CHAN);
 
     // Set user settings
-    std::cout << boost::format("\nSetting sample rate to: %d") % rate << std::endl;
+    std::cout << boost::format("Setting antenna to:     %s\n") % ant;
+    usrp->set_rx_antenna(ant, ACTIVE_CHAN);
+    std::cout << boost::format("Actual antenna:         %s\n") % usrp->get_rx_antenna(ACTIVE_CHAN);
+
+    std::cout << boost::format("Setting sample rate to: %d\n") % rate;
     usrp->set_rx_rate(rate);
-    std::cout << boost::format("Actual sample rate:     %d") % usrp->get_rx_rate() << std::endl;
+    std::cout << boost::format("Actual sample rate:     %d\n") % usrp->get_rx_rate();
 
-    std::cout << boost::format("\nSetting gain to: %d") % gain << std::endl;
+    std::cout << boost::format("Setting gain to: %d\n") % gain;
     usrp->set_rx_gain(gain);
-    std::cout << boost::format("Actual gain:     %d") % usrp->get_rx_gain() << std::endl;
+    std::cout << boost::format("Actual gain:     %d\n") % usrp->get_rx_gain();
 
-    // Get a stream from the device
+    // Get an rx_streamer from the device
     uhd::stream_args_t stream_args("fc32", "sc16");
     stream_args.channels.push_back(0);
     rx_stream = usrp->get_rx_stream(stream_args);
     recv_spb = rx_stream->get_max_num_samps();
 
     // Calculate the frequency hops
-    for(double rx_freq = start_freq; rx_freq <= end_freq; rx_freq += rate) {
+    for (double rx_freq = start_freq; rx_freq <= end_freq; rx_freq += rate) {
         rf_freqs.push_back(rx_freq);
     }
-    std::cout << boost::format("\nTotal Hops: %d") % rf_freqs.size() << std::endl;
+    std::cout << boost::format("Total Hops: %d\n") % rf_freqs.size();
 
     // Set up buffers
-    buffs = recv_buffs_t(
-        rf_freqs.size(), recv_buff_t(spb)
-        );
-    
-    while(1){
-        /*
-         * Each receive+tune time gets a set amount of time before moving on to the next. However,
-         * the software needs some lead time before the USRP starts to stream the next set of samples.
-         */
-        pipeline_timespec = uhd::time_spec_t(pipeline_time);
-        pt::time_duration polltime_ptime = pt::milliseconds(pipeline_time*1000) - pt::microseconds(20);
-        uhd::time_spec_t polltime_duration(double(polltime_ptime.total_microseconds()) / 1e9);
-
-        /*
-         * Send some initial timed commands to get started and send the rest as necessary
-         * after receiving.
-         */
-        stream_cmd.num_samps = spb;
-        stream_cmd.stream_now = false;
-        stream_cmd.time_spec = uhd::time_spec_t(0.0);
-        usrp->set_time_now(uhd::time_spec_t(0.0));
-        size_t num_initial_cmds = std::min<size_t>(X300_COMMAND_FIFO_DEPTH, rf_freqs.size());
-        for(last_cmd_index = 0; last_cmd_index < num_initial_cmds; ++last_cmd_index) {
-            stream_cmd.time_spec += pipeline_timespec;
-            rx_stream->issue_stream_cmd(stream_cmd);
-        }
-
-        std::cout << "\nScanning..." << std::flush;
-        uhd::time_spec_t start_time = uhd::time_spec_t::get_system_time();
+    buffs = recv_buffs_t(rf_freqs.size(), recv_buff_t(spb));
 
-        // The first pipeline segment is just tuning for the first receive
-        uhd::time_spec_t polltime = usrp->get_time_now() + polltime_duration;
+    // Tune the active channel to the first frequency and reset the USRP's time
+    usrp->set_rx_freq(rf_freqs[0], ACTIVE_CHAN);
+    usrp->set_time_now(uhd::time_spec_t(0.0));
 
-        // Initialize the first LO frequency
-        usrp->set_rx_freq(rf_freqs[0], ACTIVE_CHAN);
+    // Configure the stream command which will be issued to acquire samples at each frequency
+    stream_cmd.num_samps = spb;
+    stream_cmd.stream_now = false;
+    stream_cmd.time_spec = uhd::time_spec_t(0.0);
 
-        while(usrp->get_time_now() < polltime);
+    // Stream commands will be scheduled at regular intervals
+    uhd::time_spec_t receive_interval_ts = uhd::time_spec_t(receive_interval);
 
-        for (size_t i = 0; i < rf_freqs.size() - 1; i++) {
-           polltime = usrp->get_time_now() + polltime_duration;
-           
-           // Swap synthesizers by setting the LO source
-           std::string lo_src = (i % 2) ? "companion" : "internal";
-           usrp->set_rx_lo_source(lo_src, ALL_STAGES, ACTIVE_CHAN);
+    // Issue stream commands to fill the command queue on the FPGA
+    size_t num_initial_cmds = std::min<size_t>(X300_COMMAND_FIFO_DEPTH, rf_freqs.size());
+    size_t num_issued_commands;
 
-           // Preconfigure the next frequency
-           usrp->set_rx_freq(rf_freqs[i+1], UNUSED_CHAN);
+    for (num_issued_commands = 0; num_issued_commands < num_initial_cmds; num_issued_commands++) {
+        stream_cmd.time_spec += receive_interval_ts;
+        rx_stream->issue_stream_cmd(stream_cmd);
+    }
 
-           // Program the current frequency
-           // This frequency was already pre-programmed in the previous iteration
-           // so this call will only configure front-end filter, etc
-           usrp->set_rx_freq(rf_freqs[i], ACTIVE_CHAN);
+    // Hop frequencies and acquire bursts of samples at each until done sweeping
+    while(1) {
 
-           twinrx_recv(i);
+        std::cout << "Scanning..." << std::endl;
+        uhd::time_spec_t start_time = uhd::time_spec_t::get_system_time();
 
-           while(usrp->get_time_now() < polltime);
+        for (size_t i = 0; i < rf_freqs.size(); i++) {
+            // Swap the mapping of synthesizers by setting the LO source
+            // The unused channel will always
+            std::string lo_src = (i % 2) ? "companion" : "internal";
+            usrp->set_rx_lo_source(lo_src, uhd::usrp::multi_usrp::ALL_LOS, ACTIVE_CHAN);
+
+            // Preconfigure the next frequency
+            usrp->set_rx_freq(rf_freqs[(i+1) % rf_freqs.size()], UNUSED_CHAN);
+
+            // Program the current frequency
+            // This frequency was already pre-programmed in the previous iteration so the local oscillators
+            // are already tuned. This call will only configure front-end filter, amplifiers, etc
+            usrp->set_rx_freq(rf_freqs[i], ACTIVE_CHAN);
+
+            // Receive one burst of samples
+            twinrx_recv(buffs[i]);
+
+            // Schedule another acquisition if necessary
+            if (vm.count("repeat") or num_issued_commands < rf_freqs.size()) {
+                stream_cmd.time_spec += receive_interval_ts;
+                rx_stream->issue_stream_cmd(stream_cmd);
+                num_issued_commands++;
+            }
         }
 
         uhd::time_spec_t end_time = uhd::time_spec_t::get_system_time();
-        std::cout << boost::format("done in %d seconds.\n") % (end_time - start_time).get_real_secs();
+        std::cout << boost::format("Sweep done in %d milliseconds.\n") % ((end_time - start_time).get_real_secs() * 1000);
 
         // Optionally convert received samples to FFT and write to file
         if(vm.count("fft-path")) {
             write_fft_to_file(fft_path);
         }
 
-        std::cout << std::endl << "Done!" << std::endl << std::endl;
-
         if (!vm.count("repeat")){
             break;
         }
-
     }
+
+    std::cout << "Done!" << std::endl;
+
+    usrp.reset();
     return EXIT_SUCCESS;
 }