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authorJosh Blum <josh@joshknows.com>2010-08-19 19:44:01 -0700
committerJosh Blum <josh@joshknows.com>2010-08-19 19:44:01 -0700
commiteec4cd82ff0948652fb073d81b426fa9ce1ab7c5 (patch)
tree895c36811cffebb0c011fee4c2836b142e2944b2 /host/examples
parentd99e22971975e9b5bfb966741684963be8f049f6 (diff)
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uhd: work on tx waveforms to make it more accurate
Diffstat (limited to 'host/examples')
-rw-r--r--host/examples/tx_waveforms.cpp62
1 files changed, 43 insertions, 19 deletions
diff --git a/host/examples/tx_waveforms.cpp b/host/examples/tx_waveforms.cpp
index e9cf210bb..22975da96 100644
--- a/host/examples/tx_waveforms.cpp
+++ b/host/examples/tx_waveforms.cpp
@@ -20,6 +20,7 @@
#include <uhd/usrp/simple_usrp.hpp>
#include <boost/program_options.hpp>
#include <boost/thread/thread_time.hpp> //system time
+#include <boost/math/special_functions/round.hpp>
#include <boost/format.hpp>
#include <iostream>
#include <complex>
@@ -32,7 +33,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
//variables to be set by po
std::string args, wave_type;
- size_t total_duration, amspb;
+ size_t total_duration, mspb;
double rate, freq, wave_freq;
float ampl, gain;
@@ -42,7 +43,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
("help", "help message")
("args", po::value<std::string>(&args)->default_value(""), "simple uhd device address args")
("duration", po::value<size_t>(&total_duration)->default_value(3), "number of seconds to transmit")
- ("amspb", po::value<size_t>(&amspb)->default_value(10000), "approximate mimimum samples per buffer")
+ ("mspb", po::value<size_t>(&mspb)->default_value(10000), "mimimum samples per buffer")
("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 the waveform")
@@ -88,33 +89,56 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
}
//error when the waveform is not possible to generate
- if (std::abs(wave_freq)/sdev->get_tx_rate() < 0.5/amspb){
+ if (std::abs(wave_freq)/sdev->get_tx_rate() < 0.5/mspb){
throw std::runtime_error("wave freq/tx rate too small");
}
if (std::abs(wave_freq) > sdev->get_tx_rate()/2){
throw std::runtime_error("wave freq out of Nyquist zone");
}
- //fill a buffer with one period worth of samples
- std::vector<float> period(size_t(sdev->get_tx_rate()/std::abs(wave_freq)));
- std::cout << boost::format("Samples per waveform period: %d") % period.size() << std::endl;
- for (size_t n = 0; n < period.size(); n++){
- if (wave_type == "CONST") period[n] = ampl;
- else if (wave_type == "SQUARE") period[n] = (n > period.size()/2)? ampl : 0;
- else if (wave_type == "RAMP") period[n] = float((n/double(period.size()-1)) * 2*ampl - ampl);
- else if (wave_type == "SINE") period[n] = ampl*float(std::sin(2*M_PI*n/double(period.size())));
- else throw std::runtime_error("unknown waveform type: " + wave_type);
+ //how many periods should we have per buffer to mimimize error
+ double samps_per_period = sdev->get_tx_rate()/std::abs(wave_freq);
+ std::cout << boost::format("Samples per waveform period: %d") % samps_per_period << std::endl;
+ size_t periods_per_buff = std::max<size_t>(1, mspb/samps_per_period);
+ while (true){
+ double num_samps_per_buff = periods_per_buff*samps_per_period;
+ double sample_error = num_samps_per_buff - boost::math::round(num_samps_per_buff);
+ if (std::abs(sample_error/num_samps_per_buff) < 1e-5) break;
+ periods_per_buff++;
}
//allocate data to send (fill with several periods worth of IQ samples)
- const size_t periods_per_buff = std::max<size_t>(1, amspb/period.size());
- std::vector<std::complex<float> > buff(period.size()*periods_per_buff);
+ std::vector<std::complex<float> > buff(samps_per_period*periods_per_buff);
+ const double i_ahead = (wave_freq > 0)? samps_per_period/4 : 0;
+ const double q_ahead = (wave_freq < 0)? samps_per_period/4 : 0;
std::cout << boost::format("Samples per send buffer: %d") % buff.size() << std::endl;
- const size_t i_ahead = (wave_freq > 0)? period.size()/4 : 0;
- const size_t q_ahead = (wave_freq < 0)? period.size()/4 : 0;
- for (size_t n = 0; n < buff.size(); n++) buff[n] = std::complex<float>(
- period[(n+i_ahead)%period.size()], period[(n+q_ahead)%period.size()] //I,Q
- );
+ if (wave_type == "CONST"){
+ for (size_t n = 0; n < buff.size(); n++){
+ buff[n] = std::complex<float>(ampl, ampl);
+ }
+ }
+ else if (wave_type == "SQUARE"){
+ for (size_t n = 0; n < buff.size(); n++){
+ float I = (std::fmod(n+i_ahead, samps_per_period) > samps_per_period/2)? ampl : 0;
+ float Q = (std::fmod(n+q_ahead, samps_per_period) > samps_per_period/2)? ampl : 0;
+ buff[n] = std::complex<float>(I, Q);
+ }
+ }
+ else if (wave_type == "RAMP"){
+ for (size_t n = 0; n < buff.size(); n++){
+ float I = float(std::fmod(n+i_ahead, samps_per_period)/samps_per_period * 2*ampl - ampl);
+ float Q = float(std::fmod(n+q_ahead, samps_per_period)/samps_per_period * 2*ampl - ampl);
+ buff[n] = std::complex<float>(I, Q);
+ }
+ }
+ else if (wave_type == "SINE"){
+ for (size_t n = 0; n < buff.size(); n++){
+ float I = float(ampl*std::sin(2*M_PI*(n+i_ahead)/samps_per_period));
+ float Q = float(ampl*std::sin(2*M_PI*(n+q_ahead)/samps_per_period));
+ buff[n] = std::complex<float>(I, Q);
+ }
+ }
+ else throw std::runtime_error("unknown waveform type: " + wave_type);
//setup the metadata flags
uhd::tx_metadata_t md;