Transceiver52M: Allow startup delay for stream alignment

UHD requires a small amount of time to align multiple streams at
startup. Delay the startup by 100 ms relative to the queried device time
(actual delay inclusive of control latencies will be less).

The following error is only relevant to dual-channel UHD devices (e.g.
Fairwaves UmTRX and Ettus B210).

UHD Error:
    The receive packet handler failed to time-align packets.
    1002 received packets were processed by the handler.
    However, a timestamp match could not be determined.

Signed-off-by: Thomas Tsou <tom@tsou.cc>

1 files changed, 11 insertions, 5 deletions

diff --git a/Transceiver52M/UHDDevice.cpp b/Transceiver52M/UHDDevice.cpp
index 875fe47..a15e5f1 100644
--- a/Transceiver52M/UHDDevice.cpp
+++ b/Transceiver52M/UHDDevice.cpp
@@ -263,7 +263,7 @@ public:
 	int open(const std::string &args, bool extref);
 	bool start();
 	bool stop();
-	void restart(uhd::time_spec_t ts);
+	void restart();
 	void setPriority(float prio);
 	enum TxWindowType getWindowType() { return tx_window; }
 
@@ -737,12 +737,18 @@ bool uhd_device::flush_recv(size_t num_pkts)
 	return true;
 }
 
-void uhd_device::restart(uhd::time_spec_t)
+void uhd_device::restart()
 {
+	/* Allow 100 ms delay to align multi-channel streams */
+	double delay = 0.1;
+
 	aligned = false;
 
+	uhd::time_spec_t current = usrp_dev->get_time_now();
+
 	uhd::stream_cmd_t cmd = uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS;
-	cmd.stream_now = true;
+	cmd.stream_now = false;
+	cmd.time_spec = uhd::time_spec_t(current.get_real_secs() + delay);
 
 	usrp_dev->issue_stream_cmd(cmd);
 
@@ -765,7 +771,7 @@ bool uhd_device::start()
 	async_event_thrd.start((void * (*)(void*))async_event_loop, (void*)this);
 
 	// Start streaming
-	restart(uhd::time_spec_t(0.0));
+	restart();
 
 	// Display usrp time
 	double time_now = usrp_dev->get_time_now().get_real_secs();
@@ -886,7 +892,7 @@ int uhd_device::readSamples(std::vector<short *> &bufs, int len, bool *overrun,
 			LOG(ALERT) << "UHD: Unrecoverable error, exiting...";
 			exit(-1);
 		case ERROR_TIMING:
-			restart(prev_ts);
+			restart();
 		case ERROR_UNHANDLED:
 			continue;
 		}