Getting Started with UHD and C++
From Ettus Knowledge Base
Application Note Number
AN-204
Revision History
| Date | Author | Details |
|---|---|---|
| 2016-05-01 | Neel Pandeya Nate Temple |
Initial creation |
Abstract
This AN explains how to write and build C++ programs that use the UHD API.
Overview
This Application Note will walk through building a basic C++ program with UHD. This program will initialize, configure the USRP device, set the sample rate, frequency, gain, bandwidth, and select the antenna.
Example code:
#include <uhd/utils/thread_priority.hpp>
#include <uhd/utils/safe_main.hpp>
#include <uhd/usrp/multi_usrp.hpp>
#include <uhd/exception.hpp>
#include <uhd/types/tune_request.hpp>
#include <boost/program_options.hpp>
#include <boost/format.hpp>
#include <boost/thread.hpp>
#include <iostream>
int UHD_SAFE_MAIN(int argc, char *argv[]) {
uhd::set_thread_priority_safe();
std::string device_args("addr=192.168.10.2");
std::string subdev("A:0");
std::string ant("TX/RX");
std::string ref("internal");
double rate(1e6);
double freq(915e6);
double gain(10);
double bw(1e6);
//create a usrp device
std::cout << std::endl;
std::cout << boost::format("Creating the usrp device with: %s...") % device_args << std::endl;
uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(device_args);
// Lock mboard clocks
std::cout << boost::format("Lock mboard clocks: %f") % ref << std::endl;
usrp->set_clock_source(ref);
//always select the subdevice first, the channel mapping affects the other settings
std::cout << boost::format("subdev set to: %f") % subdev << std::endl;
usrp->set_rx_subdev_spec(subdev);
std::cout << boost::format("Using Device: %s") % usrp->get_pp_string() << std::endl;
//set the sample rate
if (rate <= 0.0) {
std::cerr << "Please specify a valid sample rate" << std::endl;
return ~0;
}
// set sample rate
std::cout << boost::format("Setting RX Rate: %f Msps...") % (rate / 1e6) << std::endl;
usrp->set_rx_rate(rate);
std::cout << boost::format("Actual RX Rate: %f Msps...") % (usrp->get_rx_rate() / 1e6) << std::endl << std::endl;
// set freq
std::cout << boost::format("Setting RX Freq: %f MHz...") % (freq / 1e6) << std::endl;
uhd::tune_request_t tune_request(freq);
usrp->set_rx_freq(tune_request);
std::cout << boost::format("Actual RX Freq: %f MHz...") % (usrp->get_rx_freq() / 1e6) << std::endl << std::endl;
// set the rf gain
std::cout << boost::format("Setting RX Gain: %f dB...") % gain << std::endl;
usrp->set_rx_gain(gain);
std::cout << boost::format("Actual RX Gain: %f dB...") % usrp->get_rx_gain() << std::endl << std::endl;
// set the IF filter bandwidth
std::cout << boost::format("Setting RX Bandwidth: %f MHz...") % (bw / 1e6) << std::endl;
usrp->set_rx_bandwidth(bw);
std::cout << boost::format("Actual RX Bandwidth: %f MHz...") % (usrp->get_rx_bandwidth() / 1e6) << std::endl << std::endl;
// set the antenna
std::cout << boost::format("Setting RX Antenna: %s") % ant << std::endl;
usrp->set_rx_antenna(ant);
std::cout << boost::format("Actual RX Antenna: %s") % usrp->get_rx_antenna() << std::endl << std::endl;
return EXIT_SUCCESS;
}
Use the uhd/host/examples/init_usrp/CMakeLists.txt file as template - Add the names of your C++ source files to the add_executable(...) section - Put both modified CMakeLists.txt file and C++ file into an empty folder - Create a “build” folder and invoke CMake the usual way:
mkdir build cd build cmake ../ make -j4
//
// Copyright 2011-2015 Ettus Research LLC
//
// This program 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 of the License, or
// (at your option) any later version.
//
// This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
//
#include <uhd/utils/thread_priority.hpp>
#include <uhd/convert.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/thread.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/lexical_cast.hpp>
//#include <boost/atomic.hpp>
#include <iostream>
#include <complex>
#include <cstdlib>
namespace po = boost::program_options;
const double INIT_DELAY = 0.05; // 50mS initial delay before transmit
//typedef boost::atomic<bool> atomic_bool;
// We'll fake atomic bools for now, for more backward compat.
// This is just an example, after all.
typedef bool atomic_bool;
/***********************************************************************
* Test result variables
**********************************************************************/
unsigned long long num_overflows = 0;
unsigned long long num_underflows = 0;
unsigned long long num_rx_samps = 0;
unsigned long long num_tx_samps = 0;
unsigned long long num_dropped_samps = 0;
unsigned long long num_seq_errors = 0;
unsigned long long num_timeouts = 0;
/***********************************************************************
* Benchmark RX Rate
**********************************************************************/
void benchmark_rx_rate(
uhd::usrp::multi_usrp::sptr usrp,
const std::string &rx_cpu,
uhd::rx_streamer::sptr rx_stream,
bool random_nsamps,
atomic_bool& burst_timer_elapsed
) {
uhd::set_thread_priority_safe();
//print pre-test summary
std::cout << boost::format(
"Testing receive rate %f Msps on %u channels"
) % (usrp->get_rx_rate()/1e6) % rx_stream->get_num_channels() << std::endl;
//setup variables and allocate buffer
uhd::rx_metadata_t md;
const size_t max_samps_per_packet = rx_stream->get_max_num_samps();
std::vector<char> buff(max_samps_per_packet*uhd::convert::get_bytes_per_item(rx_cpu));
std::vector<void *> buffs;
for (size_t ch = 0; ch < rx_stream->get_num_channels(); ch++)
buffs.push_back(&buff.front()); //same buffer for each channel
bool had_an_overflow = false;
uhd::time_spec_t last_time;
const double rate = usrp->get_rx_rate();
uhd::stream_cmd_t cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
cmd.time_spec = usrp->get_time_now() + uhd::time_spec_t(INIT_DELAY);
cmd.stream_now = (buffs.size() == 1);
rx_stream->issue_stream_cmd(cmd);
const float burst_pkt_time = std::max(0.100, (2 * max_samps_per_packet/rate));
float recv_timeout = burst_pkt_time + INIT_DELAY;
while (true) {
//if (burst_timer_elapsed.load(boost::memory_order_relaxed)) {
if (burst_timer_elapsed) {
rx_stream->issue_stream_cmd(uhd::stream_cmd_t::STREAM_MODE_STOP_CONTINUOUS);
}
if (random_nsamps) {
cmd.num_samps = rand() % max_samps_per_packet;
rx_stream->issue_stream_cmd(cmd);
}
try {
num_rx_samps += rx_stream->recv(buffs, max_samps_per_packet, md, recv_timeout)*rx_stream->get_num_channels();
recv_timeout = burst_pkt_time;
}
catch (uhd::io_error &e) {
std::cerr << "Caught an IO exception. " << std::endl;
std::cerr << e.what() << std::endl;
return;
}
//handle the error codes
switch(md.error_code){
case uhd::rx_metadata_t::ERROR_CODE_NONE:
if (had_an_overflow){
had_an_overflow = false;
num_dropped_samps += (md.time_spec - last_time).to_ticks(rate);
}
break;
// ERROR_CODE_OVERFLOW can indicate overflow or sequence error
case uhd::rx_metadata_t::ERROR_CODE_OVERFLOW:
last_time = md.time_spec;
had_an_overflow = true;
// check out_of_sequence flag to see if it was a sequence error or overflow
if (!md.out_of_sequence)
num_overflows++;
break;
case uhd::rx_metadata_t::ERROR_CODE_TIMEOUT:
// If we stopped the streamer, then we expect this at some point
//if (burst_timer_elapsed.load(boost::memory_order_relaxed)) {
if (burst_timer_elapsed) {
return;
}
std::cerr << "Receiver error: " << md.strerror() << ", continuing..." << std::endl;
num_timeouts++;
break;
// Otherwise, it's an error
default:
std::cerr << "Receiver error: " << md.strerror() << std::endl;
std::cerr << "Unexpected error on recv, continuing..." << std::endl;
break;
}
}
}
/***********************************************************************
* Benchmark TX Rate
**********************************************************************/
void benchmark_tx_rate(
uhd::usrp::multi_usrp::sptr usrp,
const std::string &tx_cpu,
uhd::tx_streamer::sptr tx_stream,
atomic_bool& burst_timer_elapsed,
bool random_nsamps=false
) {
uhd::set_thread_priority_safe();
//print pre-test summary
std::cout << boost::format(
"Testing transmit rate %f Msps on %u channels"
) % (usrp->get_tx_rate()/1e6) % tx_stream->get_num_channels() << std::endl;
//setup variables and allocate buffer
uhd::tx_metadata_t md;
md.time_spec = usrp->get_time_now() + uhd::time_spec_t(INIT_DELAY);
md.has_time_spec = (tx_stream->get_num_channels() > 1);
const size_t max_samps_per_packet = tx_stream->get_max_num_samps();
std::vector<char> buff(max_samps_per_packet*uhd::convert::get_bytes_per_item(tx_cpu));
std::vector<const void *> buffs;
for (size_t ch = 0; ch < tx_stream->get_num_channels(); ch++)
buffs.push_back(&buff.front()); //same buffer for each channel
md.has_time_spec = (buffs.size() != 1);
if (random_nsamps) {
std::srand((unsigned int)time(NULL));
//while (not burst_timer_elapsed.load(boost::memory_order_relaxed)) {
while (not burst_timer_elapsed) {
size_t total_num_samps = rand() % max_samps_per_packet;
size_t num_acc_samps = 0;
const float timeout = 1;
usrp->set_time_now(uhd::time_spec_t(0.0));
while(num_acc_samps < total_num_samps){
//send a single packet
num_tx_samps += tx_stream->send(buffs, max_samps_per_packet, md, timeout)*tx_stream->get_num_channels();
num_acc_samps += std::min(total_num_samps-num_acc_samps, tx_stream->get_max_num_samps());
}
}
} else {
//while (not burst_timer_elapsed.load(boost::memory_order_relaxed)) {
while (not burst_timer_elapsed) {
num_tx_samps += tx_stream->send(buffs, max_samps_per_packet, md)*tx_stream->get_num_channels();
md.has_time_spec = false;
}
}
//send a mini EOB packet
md.end_of_burst = true;
tx_stream->send(buffs, 0, md);
}
void benchmark_tx_rate_async_helper(
uhd::tx_streamer::sptr tx_stream,
atomic_bool& burst_timer_elapsed
) {
//setup variables and allocate buffer
uhd::async_metadata_t async_md;
bool exit_flag = false;
while (true) {
//if (burst_timer_elapsed.load(boost::memory_order_relaxed)) {
if (burst_timer_elapsed) {
exit_flag = true;
}
if (not tx_stream->recv_async_msg(async_md)) {
if (exit_flag == true)
return;
continue;
}
//handle the error codes
switch(async_md.event_code){
case uhd::async_metadata_t::EVENT_CODE_BURST_ACK:
return;
case uhd::async_metadata_t::EVENT_CODE_UNDERFLOW:
case uhd::async_metadata_t::EVENT_CODE_UNDERFLOW_IN_PACKET:
num_underflows++;
break;
case uhd::async_metadata_t::EVENT_CODE_SEQ_ERROR:
case uhd::async_metadata_t::EVENT_CODE_SEQ_ERROR_IN_BURST:
num_seq_errors++;
break;
default:
std::cerr << "Event code: " << async_md.event_code << std::endl;
std::cerr << "Unexpected event on async recv, continuing..." << std::endl;
break;
}
}
}
/***********************************************************************
* Main code + dispatcher
**********************************************************************/
int UHD_SAFE_MAIN(int argc, char *argv[]){
uhd::set_thread_priority_safe();
//variables to be set by po
std::string args;
double duration;
double rx_rate, tx_rate;
std::string rx_otw, tx_otw;
std::string rx_cpu, tx_cpu;
std::string mode, ref, pps;
std::string channel_list;
bool random_nsamps = false;
atomic_bool burst_timer_elapsed(false);
//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")
("duration", po::value<double>(&duration)->default_value(10.0), "duration for the test in seconds")
("rx_rate", po::value<double>(&rx_rate), "specify to perform a RX rate test (sps)")
("tx_rate", po::value<double>(&tx_rate), "specify to perform a TX rate test (sps)")
("rx_otw", po::value<std::string>(&rx_otw)->default_value("sc16"), "specify the over-the-wire sample mode for RX")
("tx_otw", po::value<std::string>(&tx_otw)->default_value("sc16"), "specify the over-the-wire sample mode for TX")
("rx_cpu", po::value<std::string>(&rx_cpu)->default_value("fc32"), "specify the host/cpu sample mode for RX")
("tx_cpu", po::value<std::string>(&tx_cpu)->default_value("fc32"), "specify the host/cpu sample mode for TX")
("ref", po::value<std::string>(&ref), "clock reference (internal, external, mimo, gpsdo)")
("pps", po::value<std::string>(&pps), "PPS source (internal, external, mimo, gpsdo)")
("mode", po::value<std::string>(&mode), "DEPRECATED - use \"ref\" and \"pps\" instead (none, mimo)")
("random", "Run with random values of samples in send() and recv() to stress-test the I/O.")
("channels", po::value<std::string>(&channel_list)->default_value("0"), "which channel(s) to use (specify \"0\", \"1\", \"0,1\", etc)")
;
po::variables_map vm;
po::store(po::parse_command_line(argc, argv, desc), vm);
po::notify(vm);
//print the help message
if (vm.count("help") or (vm.count("rx_rate") + vm.count("tx_rate")) == 0){
std::cout << boost::format("UHD Benchmark Rate %s") % desc << std::endl;
std::cout <<
" Specify --rx_rate for a receive-only test.\n"
" Specify --tx_rate for a transmit-only test.\n"
" Specify both options for a full-duplex test.\n"
<< std::endl;
return ~0;
}
// Random number of samples?
if (vm.count("random")) {
std::cout << "Using random number of samples in send() and recv() calls." << std::endl;
random_nsamps = true;
}
if (vm.count("mode")) {
if (vm.count("pps") or vm.count("ref")) {
std::cout << "ERROR: The \"mode\" parameter cannot be used with the \"ref\" and \"pps\" parameters.\n" << std::endl;
return -1;
} else if (mode == "mimo") {
ref = pps = "mimo";
std::cout << "The use of the \"mode\" parameter is deprecated. Please use \"ref\" and \"pps\" parameters instead\n" << std::endl;
}
}
//create a usrp device
std::cout << std::endl;
uhd::device_addrs_t device_addrs = uhd::device::find(args, uhd::device::USRP);
if (not device_addrs.empty() and device_addrs.at(0).get("type", "") == "usrp1"){
std::cerr << "*** Warning! ***" << std::endl;
std::cerr << "Benchmark results will be inaccurate on USRP1 due to insufficient features.\n" << std::endl;
}
std::cout << boost::format("Creating the usrp device with: %s...") % args << std::endl;
uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args);
std::cout << boost::format("Using Device: %s") % usrp->get_pp_string() << std::endl;
int num_mboards = usrp->get_num_mboards();
boost::thread_group thread_group;
if(vm.count("ref"))
{
if (ref == "mimo")
{
if (num_mboards != 2) {
std::cerr << "ERROR: ref = \"mimo\" implies 2 motherboards; your system has " << num_mboards << " boards" << std::endl;
return -1;
}
usrp->set_clock_source("mimo",1);
} else {
usrp->set_clock_source(ref);
}
if(ref != "internal") {
std::cout << "Now confirming lock on clock signals..." << std::endl;
bool is_locked = false;
boost::system_time end_time = boost::get_system_time() + boost::posix_time::milliseconds(80);
for (int i = 0; i < num_mboards; i++) {
if (ref == "mimo" and i == 0) continue;
while((is_locked = usrp->get_mboard_sensor("ref_locked",i).to_bool()) == false and
boost::get_system_time() < end_time )
{
boost::this_thread::sleep(boost::posix_time::milliseconds(1));
}
if (is_locked == false) {
std::cerr << "ERROR: Unable to confirm clock signal locked on board:" << i << std::endl;
return -1;
}
is_locked = false;
}
}
}
if(vm.count("pps"))
{
if(pps == "mimo")
{
if (num_mboards != 2) {
std::cerr << "ERROR: ref = \"mimo\" implies 2 motherboards; your system has " << num_mboards << " boards" << std::endl;
return -1;
}
//make mboard 1 a slave over the MIMO Cable
usrp->set_time_source("mimo", 1);
} else {
usrp->set_time_source(pps);
}
}
//detect which channels to use
std::vector<std::string> channel_strings;
std::vector<size_t> channel_nums;
boost::split(channel_strings, channel_list, boost::is_any_of("\"',"));
for(size_t ch = 0; ch < channel_strings.size(); ch++){
size_t chan = boost::lexical_cast<int>(channel_strings[ch]);
if(chan >= usrp->get_tx_num_channels() or chan >= usrp->get_rx_num_channels()){
throw std::runtime_error("Invalid channel(s) specified.");
}
else channel_nums.push_back(boost::lexical_cast<int>(channel_strings[ch]));
}
std::cout << boost::format("Setting device timestamp to 0...") << std::endl;
if (pps == "mimo" or ref == "mimo" or channel_nums.size() == 1) {
usrp->set_time_now(0.0);
} else {
usrp->set_time_unknown_pps(uhd::time_spec_t(0.0));
}
//spawn the receive test thread
if (vm.count("rx_rate")){
usrp->set_rx_rate(rx_rate);
//create a receive streamer
uhd::stream_args_t stream_args(rx_cpu, rx_otw);
stream_args.channels = channel_nums;
uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);
thread_group.create_thread(boost::bind(&benchmark_rx_rate, usrp, rx_cpu, rx_stream, random_nsamps, boost::ref(burst_timer_elapsed)));
}
//spawn the transmit test thread
if (vm.count("tx_rate")){
usrp->set_tx_rate(tx_rate);
//create a transmit streamer
uhd::stream_args_t stream_args(tx_cpu, tx_otw);
stream_args.channels = channel_nums;
uhd::tx_streamer::sptr tx_stream = usrp->get_tx_stream(stream_args);
thread_group.create_thread(boost::bind(&benchmark_tx_rate, usrp, tx_cpu, tx_stream, boost::ref(burst_timer_elapsed), random_nsamps));
thread_group.create_thread(boost::bind(&benchmark_tx_rate_async_helper, tx_stream, boost::ref(burst_timer_elapsed)));
}
//sleep for the required duration
const long secs = long(duration);
const long usecs = long((duration - secs)*1e6);
boost::this_thread::sleep(boost::posix_time::seconds(secs) + boost::posix_time::microseconds(usecs));
//interrupt and join the threads
//burst_timer_elapsed.store(true, boost::memory_order_relaxed);
burst_timer_elapsed = true;
thread_group.join_all();
//print summary
std::cout << std::endl << boost::format(
"Benchmark rate summary:\n"
" Num received samples: %u\n"
" Num dropped samples: %u\n"
" Num overflows detected: %u\n"
" Num transmitted samples: %u\n"
" Num sequence errors: %u\n"
" Num underflows detected: %u\n"
" Num timeouts: %u\n"
) % num_rx_samps % num_dropped_samps
% num_overflows % num_tx_samps
% num_seq_errors % num_underflows
% num_timeouts << std::endl;
//finished
std::cout << std::endl << "Done!" << std::endl << std::endl;
return EXIT_SUCCESS;
}