Move USRP GPSDO and time handling into separate class

10 files changed, 496 insertions, 299 deletions

diff --git a/Makefile.am b/Makefile.am
index 6e5c1a3..2d56842 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -90,6 +90,8 @@ odr_dabmod_SOURCES  = src/DabMod.cpp \
 					  src/output/Soapy.h \
 					  src/output/UHD.cpp \
 					  src/output/UHD.h \
+					  src/output/USRPTime.cpp \
+					  src/output/USRPTime.h \
 					  src/InputFileReader.cpp \
 					  src/InputMemory.cpp \
 					  src/InputMemory.h \
diff --git a/TODO b/TODO
index c175926..cf7f9df 100644
--- a/TODO
+++ b/TODO
@@ -15,12 +15,14 @@ This would enable SFN support with LimeSDR devices.
 
 Move dpd port from uhd section to somewhere else.
 
-Clean up and separate GPS and refclk checks. Ensure muting is set properly at startup.
+Clean up and separate GPS and refclk checks.
+ * *done* handle UHD GPSDO and time
+ * handle SoapySDR time
+ * Add refclk stuff and timestamps to Soapy.
+ * Ensure muting is set properly at startup.
 
 Add antenna selection to config.
 
-Add refclk stuff and timestamps to Soapy.
-
 *done* Make an abstraction for the DPD feedback server, use it for Soapy and UHD.
 
 Move staticdelay into a new process block
diff --git a/src/Utils.cpp b/src/Utils.cpp
index cd116c7..385253b 100644
--- a/src/Utils.cpp
+++ b/src/Utils.cpp
@@ -210,3 +210,17 @@ double parseChannel(const std::string& chan)
     }
     return freq;
 }
+
+int transmission_frame_duration_ms(unsigned int dabMode)
+{
+    switch (dabMode) {
+        case 1: return 96;
+        case 2: return 24;
+        case 3: return 24;
+        case 4: return 48;
+        default:
+            throw std::runtime_error("invalid DAB mode");
+    }
+}
+
+
diff --git a/src/Utils.h b/src/Utils.h
index 8da3a1b..2bc6cb3 100644
--- a/src/Utils.h
+++ b/src/Utils.h
@@ -67,3 +67,7 @@ void set_thread_name(const char *name);
 // Convert a channel like 10A to a frequency
 double parseChannel(const std::string& chan);
 
+// dabMode is either 1, 2, 3, 4, corresponding to TM I, TM II, TM III and TM IV.
+// throws a runtime_error if dabMode is not one of these values.
+int transmission_frame_duration_ms(unsigned int dabMode);
+
diff --git a/src/output/SDR.cpp b/src/output/SDR.cpp
index 356ae4f..ac25061 100644
--- a/src/output/SDR.cpp
+++ b/src/output/SDR.cpp
@@ -63,9 +63,12 @@ SDR::SDR(SDRDeviceConfig& config, std::shared_ptr<SDRDevice> device) :
     m_running(false),
     m_device(device)
 {
-    // muting is remote-controllable, and reset by the GPS fix check
+    // muting is remote-controllable
     m_config.muting = false;
 
+    time_last_frame.tv_sec = 0;
+    time_last_frame.tv_nsec = 0;
+
     m_device_thread = std::thread(&SDR::process_thread_entry, this);
 
     m_dpd_feedback_server = make_shared<DPDFeedbackServer>(
@@ -95,11 +98,6 @@ void SDR::stop()
 int SDR::process(Buffer *dataIn)
 {
     if (m_device) {
-        if (not m_device->is_clk_source_ok()) {
-            // Ignore frame
-            return dataIn->getLength();
-        }
-
         FrameData frame;
         frame.buf.resize(dataIn->getLength());
 
@@ -210,6 +208,37 @@ void SDR::setETISource(EtiSource *etiSource)
     m_eti_source = etiSource;
 }
 
+void SDR::sleep_through_frame()
+{
+    struct timespec now;
+    if (clock_gettime(CLOCK_MONOTONIC, &now) != 0) {
+        stringstream ss;
+        ss << "clock_gettime failure: " << strerror(errno);
+        throw runtime_error(ss.str());
+    }
+
+    if (time_last_frame.tv_sec == 0) {
+        if (clock_gettime(CLOCK_MONOTONIC, &time_last_frame) != 0) {
+            stringstream ss;
+            ss << "clock_gettime failure: " << strerror(errno);
+            throw runtime_error(ss.str());
+        }
+    }
+
+    long delta_us = timespecdiff_us(time_last_frame, now);
+    long wait_time_us = transmission_frame_duration_ms(m_config.dabMode);
+
+    if (wait_time_us - delta_us > 0) {
+        usleep(wait_time_us - delta_us);
+    }
+
+    time_last_frame.tv_nsec += wait_time_us * 1000;
+    while (time_last_frame.tv_nsec >= 1000000000L) {
+        time_last_frame.tv_nsec -= 1000000000L;
+        time_last_frame.tv_sec++;
+    }
+}
+
 void SDR::handle_frame(struct FrameData& frame)
 {
     // Assumes m_device is valid
@@ -217,6 +246,7 @@ void SDR::handle_frame(struct FrameData& frame)
     constexpr double tx_timeout = 20.0;
 
     if (not m_device->is_clk_source_ok()) {
+        sleep_through_frame();
         return;
     }
 
diff --git a/src/output/SDR.h b/src/output/SDR.h
index 5593ce3..d3693da 100644
--- a/src/output/SDR.h
+++ b/src/output/SDR.h
@@ -70,6 +70,7 @@ class SDR : public ModOutput, public RemoteControllable {
         void stop(void);
         void process_thread_entry(void);
         void handle_frame(struct FrameData &frame);
+        void sleep_through_frame(void);
 
         SDRDeviceConfig& m_config;
 
@@ -87,6 +88,9 @@ class SDR : public ModOutput, public RemoteControllable {
         bool     last_tx_time_initialised = false;
         uint32_t last_tx_second = 0;
         uint32_t last_tx_pps = 0;
+
+        struct timespec time_last_frame;
+
 };
 
 }
diff --git a/src/output/UHD.cpp b/src/output/UHD.cpp
index 54ff6c2..55beacc 100644
--- a/src/output/UHD.cpp
+++ b/src/output/UHD.cpp
@@ -28,6 +28,9 @@
 
 #ifdef HAVE_OUTPUT_UHD
 
+//#define MDEBUG(fmt, args...) fprintf(LOG, fmt , ## args)
+#define MDEBUG(fmt, args...)
+
 #include "PcDebug.h"
 #include "Log.h"
 #include "RemoteControl.h"
@@ -81,46 +84,6 @@ static void uhd_msg_handler(uhd::msg::type_t type, const std::string &msg)
 }
 
 
-// Check function for GPS TIMELOCK sensor from the ODR LEA-M8F board GPSDO
-static bool check_gps_timelock(uhd::usrp::multi_usrp::sptr usrp)
-{
-    try {
-        std::string sensor_value(
-                usrp->get_mboard_sensor("gps_timelock", 0).to_pp_string());
-
-        if (sensor_value.find("TIME LOCKED") == std::string::npos) {
-            etiLog.level(warn) << "OutputUHD: gps_timelock " << sensor_value;
-            return false;
-        }
-
-        return true;
-    }
-    catch (uhd::lookup_error &e) {
-        etiLog.level(warn) << "OutputUHD: no gps_timelock sensor";
-        return false;
-    }
-}
-
-// Check function for GPS LOCKED sensor from the Ettus GPSDO
-static bool check_gps_locked(uhd::usrp::multi_usrp::sptr usrp)
-{
-    try {
-        uhd::sensor_value_t sensor_value(
-                usrp->get_mboard_sensor("gps_locked", 0));
-        if (not sensor_value.to_bool()) {
-            etiLog.level(warn) << "OutputUHD: gps_locked " <<
-                sensor_value.to_pp_string();
-            return false;
-        }
-
-        return true;
-    }
-    catch (uhd::lookup_error &e) {
-        etiLog.level(warn) << "OutputUHD: no gps_locked sensor";
-        return false;
-    }
-}
-
 
 UHD::UHD(
         SDRDeviceConfig& config) :
@@ -128,11 +91,6 @@ UHD::UHD(
     m_conf(config),
     m_running(false)
 {
-    // Variables needed for GPS fix check
-    first_gps_fix_check.tv_sec = 0;
-    last_gps_fix_check.tv_sec = 0;
-    time_last_frame.tv_sec = 0;
-
     std::stringstream device;
     device << m_conf.device;
 
@@ -183,6 +141,8 @@ UHD::UHD(
     }
     m_usrp->set_time_source(m_conf.pps_src);
 
+    m_device_time = std::make_shared<USRPTime>(m_usrp, m_conf);
+
     if (m_conf.subDevice != "") {
         m_usrp->set_tx_subdev_spec(uhd::usrp::subdev_spec_t(m_conf.subDevice),
                 uhd::usrp::multi_usrp::ALL_MBOARDS);
@@ -388,8 +348,34 @@ size_t UHD::receive_frame(
 // Return true if GPS and reference clock inputs are ok
 bool UHD::is_clk_source_ok(void)
 {
-    //TODO
-    return true;
+    bool ok = true;
+
+    if (refclk_loss_needs_check()) {
+        try {
+            if (not m_usrp->get_mboard_sensor("ref_locked", 0).to_bool()) {
+                ok = false;
+
+                etiLog.level(alert) <<
+                    "OutputUHD: External reference clock lock lost !";
+
+                if (m_conf.refclk_lock_loss_behaviour == CRASH) {
+                    throw std::runtime_error(
+                            "OutputUHD: External reference clock lock lost.");
+                }
+            }
+        }
+        catch (uhd::lookup_error &e) {
+            suppress_refclk_loss_check = true;
+            etiLog.log(warn, "OutputUHD: This USRP does not have mboard "
+                    "sensor for ext clock loss. Check disabled.");
+        }
+    }
+
+    if (m_device_time) {
+        ok |= m_device_time->verify_time();
+    }
+
+    return ok;
 }
 
 const char* UHD::device_name(void)
@@ -406,27 +392,6 @@ bool UHD::refclk_loss_needs_check() const
     return m_conf.refclk_src != "internal";
 }
 
-bool UHD::gpsfix_needs_check() const
-{
-    if (m_conf.refclk_src == "internal") {
-        return false;
-    }
-    else if (m_conf.refclk_src == "gpsdo") {
-        return (m_conf.maxGPSHoldoverTime != 0);
-    }
-    else if (m_conf.refclk_src == "gpsdo-ettus") {
-        return (m_conf.maxGPSHoldoverTime != 0);
-    }
-    else {
-        return false;
-    }
-}
-
-bool UHD::gpsdo_is_ettus() const
-{
-    return (m_conf.refclk_src == "gpsdo-ettus");
-}
-
 void UHD::stop_threads()
 {
     m_running.store(false);
@@ -436,197 +401,6 @@ void UHD::stop_threads()
 }
 
 
-static int transmission_frame_duration_ms(unsigned int dabMode)
-{
-    switch (dabMode) {
-        // could happen when called from constructor and we take the mode from ETI
-        case 0: return 0;
-
-        case 1: return 96;
-        case 2: return 24;
-        case 3: return 24;
-        case 4: return 48;
-        default:
-            throw std::runtime_error("OutputUHD: invalid DAB mode");
-    }
-}
-
-
-void UHD::set_usrp_time()
-{
-    if (m_conf.enableSync and (m_conf.pps_src == "none")) {
-        etiLog.level(warn) <<
-            "OutputUHD: WARNING:"
-            " you are using synchronous transmission without PPS input!";
-
-        struct timespec now;
-        if (clock_gettime(CLOCK_REALTIME, &now)) {
-            perror("OutputUHD:Error: could not get time: ");
-            etiLog.level(error) << "OutputUHD: could not get time";
-        }
-        else {
-            m_usrp->set_time_now(uhd::time_spec_t(now.tv_sec));
-            etiLog.level(info) << "OutputUHD: Setting USRP time to " <<
-                std::fixed <<
-                uhd::time_spec_t(now.tv_sec).get_real_secs();
-        }
-    }
-
-    if (m_conf.pps_src != "none") {
-        /* handling time for synchronisation: wait until the next full
-         * second, and set the USRP time at next PPS */
-        struct timespec now;
-        time_t seconds;
-        if (clock_gettime(CLOCK_REALTIME, &now)) {
-            etiLog.level(error) << "OutputUHD: could not get time :" <<
-                strerror(errno);
-            throw std::runtime_error("OutputUHD: could not get time.");
-        }
-        else {
-            seconds = now.tv_sec;
-
-            MDEBUG("OutputUHD:sec+1: %ld ; now: %ld ...\n", seconds+1, now.tv_sec);
-            while (seconds + 1 > now.tv_sec) {
-                usleep(1);
-                if (clock_gettime(CLOCK_REALTIME, &now)) {
-                    etiLog.level(error) << "OutputUHD: could not get time :" <<
-                        strerror(errno);
-                    throw std::runtime_error("OutputUHD: could not get time.");
-                }
-            }
-            MDEBUG("OutputUHD:sec+1: %ld ; now: %ld ...\n", seconds+1, now.tv_sec);
-            /* We are now shortly after the second change. */
-
-            usleep(200000); // 200ms, we want the PPS to be later
-            m_usrp->set_time_unknown_pps(uhd::time_spec_t(seconds + 2));
-            etiLog.level(info) << "OutputUHD: Setting USRP time next pps to " <<
-                std::fixed <<
-                uhd::time_spec_t(seconds + 2).get_real_secs();
-        }
-
-        usleep(1e6);
-        etiLog.log(info,  "OutputUHD: USRP time %f\n",
-                m_usrp->get_time_now().get_real_secs());
-    }
-}
-
-void UHD::initial_gps_check()
-{
-    if (first_gps_fix_check.tv_sec == 0) {
-        etiLog.level(info) << "Waiting for GPS fix";
-
-        if (clock_gettime(CLOCK_MONOTONIC, &first_gps_fix_check) != 0) {
-            stringstream ss;
-            ss << "clock_gettime failure: " << strerror(errno);
-            throw std::runtime_error(ss.str());
-        }
-    }
-
-    check_gps();
-
-    if (last_gps_fix_check.tv_sec >
-            first_gps_fix_check.tv_sec + initial_gps_fix_wait) {
-        stringstream ss;
-        ss << "GPS did not show time lock in " <<
-            initial_gps_fix_wait << " seconds";
-        throw std::runtime_error(ss.str());
-    }
-
-    if (time_last_frame.tv_sec == 0) {
-        if (clock_gettime(CLOCK_MONOTONIC, &time_last_frame) != 0) {
-            stringstream ss;
-            ss << "clock_gettime failure: " << strerror(errno);
-            throw std::runtime_error(ss.str());
-        }
-    }
-
-    struct timespec now;
-    if (clock_gettime(CLOCK_MONOTONIC, &now) != 0) {
-        stringstream ss;
-        ss << "clock_gettime failure: " << strerror(errno);
-        throw std::runtime_error(ss.str());
-    }
-
-    long delta_us = timespecdiff_us(time_last_frame, now);
-    long wait_time_us = transmission_frame_duration_ms(m_conf.dabMode);
-
-    if (wait_time_us - delta_us > 0) {
-        usleep(wait_time_us - delta_us);
-    }
-
-    time_last_frame.tv_nsec += wait_time_us * 1000;
-    if (time_last_frame.tv_nsec >= 1000000000L) {
-        time_last_frame.tv_nsec -= 1000000000L;
-        time_last_frame.tv_sec++;
-    }
-}
-
-void UHD::check_gps()
-{
-    struct timespec time_now;
-    if (clock_gettime(CLOCK_MONOTONIC, &time_now) != 0) {
-        stringstream ss;
-        ss << "clock_gettime failure: " << strerror(errno);
-        throw std::runtime_error(ss.str());
-    }
-
-    // Divide interval by two because we alternate between
-    // launch and check
-    if (gpsfix_needs_check() and
-            last_gps_fix_check.tv_sec + gps_fix_check_interval/2.0 <
-            time_now.tv_sec) {
-        last_gps_fix_check = time_now;
-
-        // Alternate between launching thread and checking the
-        // result.
-        if (gps_fix_task.joinable()) {
-            if (gps_fix_future.has_value()) {
-
-                gps_fix_future.wait();
-
-                gps_fix_task.join();
-
-                if (not gps_fix_future.get()) {
-                    if (num_checks_without_gps_fix == 0) {
-                        etiLog.level(alert) <<
-                            "OutputUHD: GPS Time Lock lost";
-                    }
-                    num_checks_without_gps_fix++;
-                }
-                else {
-                    if (num_checks_without_gps_fix) {
-                        etiLog.level(info) <<
-                            "OutputUHD: GPS Time Lock recovered";
-                    }
-                    num_checks_without_gps_fix = 0;
-                }
-
-                if (gps_fix_check_interval * num_checks_without_gps_fix >
-                        m_conf.maxGPSHoldoverTime) {
-                    std::stringstream ss;
-                    ss << "Lost GPS Time Lock for " << gps_fix_check_interval *
-                        num_checks_without_gps_fix << " seconds";
-                    throw std::runtime_error(ss.str());
-                }
-            }
-        }
-        else {
-            // Checking the sensor here takes too much
-            // time, it has to be done in a separate thread.
-            if (gpsdo_is_ettus()) {
-                gps_fix_pt = boost::packaged_task<bool>(
-                        boost::bind(check_gps_locked, m_usrp) );
-            }
-            else {
-                gps_fix_pt = boost::packaged_task<bool>(
-                        boost::bind(check_gps_timelock, m_usrp) );
-            }
-            gps_fix_future = gps_fix_pt.get_future();
-
-            gps_fix_task = boost::thread(boost::move(gps_fix_pt));
-        }
-    }
-}
 
 void UHD::print_async_thread()
 {
diff --git a/src/output/UHD.h b/src/output/UHD.h
index 5ae477b..4d3eecc 100644
--- a/src/output/UHD.h
+++ b/src/output/UHD.h
@@ -47,6 +47,7 @@ DESCRIPTION:
 
 #include "Log.h"
 #include "output/SDR.h"
+#include "output/USRPTime.h"
 #include "TimestampDecoder.h"
 #include "RemoteControl.h"
 #include "ThreadsafeQueue.h"
@@ -54,9 +55,6 @@ DESCRIPTION:
 #include <stdio.h>
 #include <sys/types.h>
 
-//#define MDEBUG(fmt, args...) fprintf(LOG, fmt , ## args)
-#define MDEBUG(fmt, args...)
-
 // If the timestamp is further in the future than
 // 100 seconds, abort
 #define TIMESTAMP_ABORT_FUTURE 100
@@ -100,6 +98,7 @@ class UHD : public Output::SDRDevice
         uhd::usrp::multi_usrp::sptr m_usrp;
         uhd::tx_streamer::sptr m_tx_stream;
         uhd::rx_streamer::sptr m_rx_stream;
+        std::shared_ptr<USRPTime> m_device_time;
 
         size_t num_underflows = 0;
         size_t num_overflows = 0;
@@ -110,21 +109,6 @@ class UHD : public Output::SDRDevice
 
         uhd::tx_metadata_t md;
 
-        // GPS Fix check variables
-        int num_checks_without_gps_fix = 1;
-        struct timespec first_gps_fix_check;
-        struct timespec last_gps_fix_check;
-        struct timespec time_last_frame;
-        boost::packaged_task<bool> gps_fix_pt;
-        boost::unique_future<bool> gps_fix_future;
-        boost::thread gps_fix_task;
-
-        // Wait time in seconds to get fix
-        static const int initial_gps_fix_wait = 180;
-
-        // Interval for checking the GPS at runtime
-        static constexpr double gps_fix_check_interval = 10.0; // seconds
-
         // Used to print statistics once a second
         std::chrono::steady_clock::time_point last_print_time;
 
@@ -132,24 +116,11 @@ class UHD : public Output::SDRDevice
         bool refclk_loss_needs_check(void) const;
         bool suppress_refclk_loss_check = false;
 
-        // Returns true if we want to check for the gps_timelock sensor
-        bool gpsfix_needs_check(void) const;
-
-        // Return true if the gpsdo is from ettus, false if it is the ODR
-        // LEA-M8F board is used
-        bool gpsdo_is_ettus(void) const;
-
         // Poll asynchronous metadata from UHD
         std::atomic<bool> m_running;
         boost::thread m_async_rx_thread;
         void stop_threads(void);
         void print_async_thread(void);
-
-        void check_gps();
-
-        void set_usrp_time();
-
-        void initial_gps_check();
 };
 
 } // namespace Output
diff --git a/src/output/USRPTime.cpp b/src/output/USRPTime.cpp
new file mode 100644
index 0000000..dcedeab
--- /dev/null
+++ b/src/output/USRPTime.cpp
@@ -0,0 +1,280 @@
+/*
+   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Her Majesty the
+   Queen in Right of Canada (Communications Research Center Canada)
+
+   Copyright (C) 2017
+   Matthias P. Braendli, matthias.braendli@mpb.li
+
+    http://opendigitalradio.org
+
+DESCRIPTION:
+   The part of the UHD output that takes care of the GPSDO.
+*/
+
+/*
+   This file is part of ODR-DabMod.
+
+   ODR-DabMod 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.
+
+   ODR-DabMod 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 ODR-DabMod.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "output/USRPTime.h"
+
+#ifdef HAVE_OUTPUT_UHD
+
+//#define MDEBUG(fmt, args...) fprintf(LOG, fmt , ## args)
+#define MDEBUG(fmt, args...)
+
+namespace Output {
+
+using namespace std;
+
+
+// Check function for GPS TIMELOCK sensor from the ODR LEA-M8F board GPSDO
+static bool check_gps_timelock(uhd::usrp::multi_usrp::sptr& usrp)
+{
+    try {
+        const string sensor_value =
+            usrp->get_mboard_sensor("gps_timelock", 0).to_pp_string();
+
+        if (sensor_value.find("TIME LOCKED") == string::npos) {
+            etiLog.level(warn) << "OutputUHD: gps_timelock " << sensor_value;
+            return false;
+        }
+
+        return true;
+    }
+    catch (const uhd::lookup_error &e) {
+        etiLog.level(warn) << "OutputUHD: no gps_timelock sensor";
+        return false;
+    }
+}
+
+// Check function for GPS LOCKED sensor from the Ettus GPSDO
+static bool check_gps_locked(uhd::usrp::multi_usrp::sptr& usrp)
+{
+    try {
+        const uhd::sensor_value_t sensor_value(
+                usrp->get_mboard_sensor("gps_locked", 0));
+        if (not sensor_value.to_bool()) {
+            etiLog.level(warn) << "OutputUHD: gps_locked " <<
+                sensor_value.to_pp_string();
+            return false;
+        }
+
+        return true;
+    }
+    catch (const uhd::lookup_error &e) {
+        etiLog.level(warn) << "OutputUHD: no gps_locked sensor";
+        return false;
+    }
+}
+
+
+USRPTime::USRPTime(
+        uhd::usrp::multi_usrp::sptr usrp,
+        SDRDeviceConfig& conf) :
+    m_usrp(usrp),
+    m_conf(conf),
+    time_last_check(timepoint_t::clock::now())
+{
+    if (m_conf.enableSync and (m_conf.pps_src == "none")) {
+        set_usrp_time_from_localtime();
+    }
+}
+
+bool USRPTime::verify_time()
+{
+    if (not gpsfix_needs_check()) {
+        return true;
+    }
+
+    /* During bootup, we say the gpsdo is not ok, and we poll the GPSDO until
+     * we reach lock. Then we sync time. If we do not reach lock in time, we
+     * crash.
+     *
+     * Once we are synced and we have lock, everything ok. If we lose lock for
+     * a number of seconds, we switch to the lost_fix state.
+     *
+     * In the lost fix state, we return false to get the TX muted, and we monitor.
+     * If the fix comes back, we unmute. If we reach the timeout, we crash.
+     */
+
+    check_gps();
+
+    const auto duration_without_fix =
+        gps_fix_check_interval * num_checks_without_gps_fix;
+
+    switch (gps_state) {
+        case gps_state_e::bootup:
+            if (duration_without_fix > initial_gps_fix_wait) {
+                throw runtime_error("GPS did not fix in " +
+                        to_string(initial_gps_fix_wait) + " seconds");
+            }
+
+            if (num_checks_without_gps_fix == 0) {
+                if (m_conf.pps_src != "none") {
+                    set_usrp_time_from_pps();
+                }
+                gps_state = gps_state_e::monitor_fix;
+                return true;
+            }
+
+            return false;
+
+        case gps_state_e::monitor_fix:
+            if (duration_without_fix > m_conf.maxGPSHoldoverTime) {
+                throw runtime_error("Lost GPS Fix for " +
+                        to_string(duration_without_fix) + " seconds");
+            }
+
+            return true;
+    }
+
+    throw logic_error("End of USRPTime::verify_time() reached");
+}
+
+void USRPTime::check_gps()
+{
+    timepoint_t time_now = timepoint_t::clock::now();
+
+    // Divide interval by two because we alternate between
+    // launch and check
+    const auto checkinterval = chrono::seconds(lrint(gps_fix_check_interval/2.0));
+
+    if (gpsfix_needs_check() and time_last_check + checkinterval < time_now) {
+        time_last_check = time_now;
+
+        // Alternate between launching thread and checking the
+        // result.
+        if (gps_fix_task.joinable()) {
+            if (gps_fix_future.has_value()) {
+
+                gps_fix_future.wait();
+
+                gps_fix_task.join();
+
+                if (not gps_fix_future.get()) {
+                    if (num_checks_without_gps_fix == 0) {
+                        etiLog.level(alert) << "OutputUHD: GPS Time Lock lost";
+                    }
+                    num_checks_without_gps_fix++;
+                }
+                else {
+                    if (num_checks_without_gps_fix) {
+                        etiLog.level(info) << "OutputUHD: GPS Time Lock recovered";
+                    }
+                    num_checks_without_gps_fix = 0;
+                }
+            }
+        }
+        else {
+            // Checking the sensor here takes too much
+            // time, it has to be done in a separate thread.
+            if (gpsdo_is_ettus()) {
+                gps_fix_pt = boost::packaged_task<bool>(
+                        boost::bind(check_gps_locked, m_usrp) );
+            }
+            else {
+                gps_fix_pt = boost::packaged_task<bool>(
+                        boost::bind(check_gps_timelock, m_usrp) );
+            }
+            gps_fix_future = gps_fix_pt.get_future();
+
+            gps_fix_task = boost::thread(boost::move(gps_fix_pt));
+        }
+    }
+}
+
+bool USRPTime::gpsfix_needs_check() const
+{
+    if (m_conf.refclk_src == "internal") {
+        return false;
+    }
+    else if (m_conf.refclk_src == "gpsdo") {
+        return (m_conf.maxGPSHoldoverTime != 0);
+    }
+    else if (m_conf.refclk_src == "gpsdo-ettus") {
+        return (m_conf.maxGPSHoldoverTime != 0);
+    }
+    else {
+        return false;
+    }
+}
+
+bool USRPTime::gpsdo_is_ettus() const
+{
+    return (m_conf.refclk_src == "gpsdo-ettus");
+}
+
+void USRPTime::set_usrp_time_from_localtime()
+{
+    etiLog.level(warn) <<
+        "OutputUHD: WARNING:"
+        " you are using synchronous transmission without PPS input!";
+
+    struct timespec now;
+    if (clock_gettime(CLOCK_REALTIME, &now)) {
+        etiLog.level(error) << "OutputUHD: could not get time :" <<
+            strerror(errno);
+    }
+    else {
+        const uhd::time_spec_t t(now.tv_sec, (double)now.tv_nsec / 1e9);
+        m_usrp->set_time_now(t);
+        etiLog.level(info) << "OutputUHD: Setting USRP time to " <<
+            std::fixed << t.get_real_secs();
+    }
+}
+
+void USRPTime::set_usrp_time_from_pps()
+{
+    /* handling time for synchronisation: wait until the next full
+     * second, and set the USRP time at next PPS */
+    struct timespec now;
+    time_t seconds;
+    if (clock_gettime(CLOCK_REALTIME, &now)) {
+        etiLog.level(error) << "OutputUHD: could not get time :" <<
+            strerror(errno);
+        throw std::runtime_error("OutputUHD: could not get time.");
+    }
+    else {
+        seconds = now.tv_sec;
+
+        MDEBUG("OutputUHD:sec+1: %ld ; now: %ld ...\n", seconds+1, now.tv_sec);
+        while (seconds + 1 > now.tv_sec) {
+            usleep(1);
+            if (clock_gettime(CLOCK_REALTIME, &now)) {
+                etiLog.level(error) << "OutputUHD: could not get time :" <<
+                    strerror(errno);
+                throw std::runtime_error("OutputUHD: could not get time.");
+            }
+        }
+        MDEBUG("OutputUHD:sec+1: %ld ; now: %ld ...\n", seconds+1, now.tv_sec);
+        /* We are now shortly after the second change. */
+
+        usleep(200000); // 200ms, we want the PPS to be later
+        m_usrp->set_time_unknown_pps(uhd::time_spec_t(seconds + 2));
+        etiLog.level(info) << "OutputUHD: Setting USRP time next pps to " <<
+            std::fixed <<
+            uhd::time_spec_t(seconds + 2).get_real_secs();
+    }
+
+    usleep(1e6);
+    etiLog.log(info,  "OutputUHD: USRP time %f\n",
+            m_usrp->get_time_now().get_real_secs());
+}
+
+
+} // namespace Output
+
+#endif // HAVE_OUTPUT_UHD
diff --git a/src/output/USRPTime.h b/src/output/USRPTime.h
new file mode 100644
index 0000000..7527f21
--- /dev/null
+++ b/src/output/USRPTime.h
@@ -0,0 +1,116 @@
+/*
+   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Her Majesty the
+   Queen in Right of Canada (Communications Research Center Canada)
+
+   Copyright (C) 2017
+   Matthias P. Braendli, matthias.braendli@mpb.li
+
+    http://opendigitalradio.org
+
+DESCRIPTION:
+   The part of the UHD output that takes care of the GPSDO and setting device
+   time.
+*/
+
+/*
+   This file is part of ODR-DabMod.
+
+   ODR-DabMod 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.
+
+   ODR-DabMod 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 ODR-DabMod.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#ifdef HAVE_CONFIG_H
+#   include <config.h>
+#endif
+
+#ifdef HAVE_OUTPUT_UHD
+
+#include <uhd/usrp/multi_usrp.hpp>
+#include <chrono>
+#include <memory>
+#include <string>
+#include <atomic>
+
+#include "Log.h"
+#include "output/SDR.h"
+#include "TimestampDecoder.h"
+#include "RemoteControl.h"
+#include "ThreadsafeQueue.h"
+
+#include <stdio.h>
+#include <sys/types.h>
+
+namespace Output {
+
+class USRPTime {
+    public:
+        USRPTime( uhd::usrp::multi_usrp::sptr usrp,
+                SDRDeviceConfig& conf);
+
+        // Verifies the GPSDO state, that the device time is ok.
+        // Returns true if all ok.
+        // Should be called more often than the gps_fix_check_interval
+        bool verify_time(void);
+
+        // Wait time in seconds to get fix
+        static const int initial_gps_fix_wait = 180;
+
+        // Interval for checking the GPS at runtime
+        static constexpr double gps_fix_check_interval = 10.0; // seconds
+
+    private:
+        enum class gps_state_e {
+            /* At startup, the LEA-M8F GPSDO gets issued a hotstart request to
+             * make sure we will not sync time on a PPS edge that is generated
+             * while the GPSDO is in holdover. In the bootup state, we wait for
+             * the first PPS after hotstart, and then sync time.
+             */
+            bootup,
+
+            /* Once the system is up, we check lock every now and then. If the
+             * fix is lost for too long, we crash.
+             */
+            monitor_fix,
+        };
+
+        void check_gps();
+
+        uhd::usrp::multi_usrp::sptr m_usrp;
+        SDRDeviceConfig& m_conf;
+
+        gps_state_e gps_state = gps_state_e::bootup;
+        int num_checks_without_gps_fix = 1;
+
+        using timepoint_t = std::chrono::time_point<std::chrono::steady_clock>;
+        timepoint_t time_last_check;
+
+        boost::packaged_task<bool> gps_fix_pt;
+        boost::unique_future<bool> gps_fix_future;
+        boost::thread gps_fix_task;
+
+        // Returns true if we want to check for the gps_timelock sensor
+        bool gpsfix_needs_check(void) const;
+
+        // Return true if the gpsdo is from ettus, false if it is the ODR
+        // LEA-M8F board is used
+        bool gpsdo_is_ettus(void) const;
+
+        void set_usrp_time_from_localtime(void);
+        void set_usrp_time_from_pps(void);
+};
+
+} // namespace Output
+
+#endif // HAVE_OUTPUT_UHD