usrpe1xx

Set at 52MHz and 270.833ksps (1625e3/6), e100 timestamps
will roll backwards at roughly one second intervals using
continuous streaming.

Attached patch modifies rx_timed_samples to use required
values and throws on monotonic time errors.

./rx_timed_samples --nsamps 2783300 --secs .5

Truncated output:

Received packet: 506 samples, 1 full secs, 0.223039 frac secs
Received packet: 506 samples, 1 full secs, 0.224907 frac secs
Received packet: 506 samples, 1 full secs, 0.226776 frac secs
Received packet: 506 samples, 1 full secs, 0.228644 frac secs
Received packet: 506 samples, 1 full secs, 0.230512 frac secs
Received packet: 506 samples, 1 full secs, 0.001611 frac secs
Error: Non-monotonic time detected

---
 host/examples/rx_timed_samples.cpp |   22 +++++++++++++++++++---
 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/host/examples/rx_timed_samples.cpp b/host/examples/rx_timed_samples.cpp
index 28d7ee4..9b6361f 100644
--- a/host/examples/rx_timed_samples.cpp
+++ b/host/examples/rx_timed_samples.cpp
@@ -41,8 +41,8 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args")
         ("secs", po::value<double>(&seconds_in_future)->default_value(1.5), "number of seconds in the future to receive")
         ("nsamps", po::value<size_t>(&total_num_samps)->default_value(10000), "total number of samples to receive")
-        ("clock", po::value<double>(&clock), "master clock frequency in Hz")
-        ("rate", po::value<double>(&rate)->default_value(100e6/16), "rate of incoming samples")
+        ("clock", po::value<double>(&clock)->default_value(52e6), "master clock frequency in Hz")
+        ("rate", po::value<double>(&rate)->default_value(1625e3/6), "rate of incoming samples")
         ("dilv", "specify to disable inner-loop verbose")
     ;
     po::variables_map vm;
@@ -82,12 +82,14 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     std::cout << boost::format(
         "Begin streaming %u samples, %f 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);
+    uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
     stream_cmd.num_samps = total_num_samps;
     stream_cmd.stream_now = false;
     stream_cmd.time_spec = uhd::time_spec_t(seconds_in_future);
     usrp->issue_stream_cmd(stream_cmd);

+    uhd::stream_cmd_t stop_cmd(uhd::stream_cmd_t::STREAM_MODE_STOP_CONTINUOUS);
+
     //meta-data will be filled in by recv()
     uhd::rx_metadata_t md;

@@ -97,6 +99,9 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
     //the first call to recv() will block this many seconds before receiving
     double timeout = seconds_in_future + 0.1; //timeout (delay before receive + padding)

+    //track previous packet timestamp
+    uhd::time_spec_t prev_ts(0,0);
+
     size_t num_acc_samps = 0; //number of accumulated samples
     while(num_acc_samps < total_num_samps){
         //receive a single packet
@@ -112,6 +117,7 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
         //handle the error code
         if (md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT) break;
         if (md.error_code != uhd::rx_metadata_t::ERROR_CODE_NONE){
+            usrp->issue_stream_cmd(stop_cmd);
             throw std::runtime_error(str(boost::format(
                 "Unexpected error code 0x%x" 
             ) % md.error_code));
@@ -121,9 +127,19 @@ int UHD_SAFE_MAIN(int argc, char *argv[]){
             "Received 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;

+       //check for monotonicity
+        if (md.time_spec < prev_ts) {
+            usrp->issue_stream_cmd(stop_cmd);
+            throw std::runtime_error("Non-monotonic time detected");
+        }
+        else {
+            prev_ts = md.time_spec;
+        }
+
         num_acc_samps += num_rx_samps;
     }

+    usrp->issue_stream_cmd(stop_cmd);
     if (num_acc_samps < total_num_samps) std::cerr << "Receive timeout before all samples received..." << std::endl;

     //finished
-- 
1.7.0.2