From 8eb2b6842570af606c797d1bc8da55bb27487b99 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Sat, 25 Feb 2017 12:05:34 +0100
Subject: Add ability to set UHD LO offset

---
 src/DabMod.cpp    |  1 +
 src/OutputUHD.cpp | 26 +++++++++++++++++++++++---
 src/OutputUHD.h   |  1 +
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/DabMod.cpp b/src/DabMod.cpp
index 37db71a..741ac73 100644
--- a/src/DabMod.cpp
+++ b/src/DabMod.cpp
@@ -503,6 +503,7 @@ int launch_modulator(int argc, char* argv[])
                 throw std::runtime_error("Configuration error");
             }
 
+            outputuhd_conf.lo_offset = pt.get<double>("uhdoutput.lo_offset", 0);
 
             outputuhd_conf.refclk_src = pt.get("uhdoutput.refclk_source", "internal");
             outputuhd_conf.pps_src = pt.get("uhdoutput.pps_source", "none");
diff --git a/src/OutputUHD.cpp b/src/OutputUHD.cpp
index 7f880e0..072b63a 100644
--- a/src/OutputUHD.cpp
+++ b/src/OutputUHD.cpp
@@ -221,9 +221,29 @@ OutputUHD::OutputUHD(
         throw std::runtime_error("Cannot set USRP sample rate. Aborted.");
     }
 
-    //set the centre frequency
-    MDEBUG("OutputUHD:Setting freq to %f...\n", myConf.frequency);
-    myUsrp->set_tx_freq(myConf.frequency);
+    if (myConf.lo_offset != 0.0) {
+        etiLog.log(info, "OutputUHD:Setting freq to %f with LO offset %f...\n",
+                myConf.frequency, myConf.lo_offset);
+        const auto tr = uhd::tune_request_t(myConf.frequency, myConf.lo_offset);
+        uhd::tune_result_t result = myUsrp->set_tx_freq(tr);
+
+        etiLog.level(info) << "OutputUHD: " << std::fixed <<
+            "Target RF: " << result.target_rf_freq <<
+            "Actual RF: " << result.actual_rf_freq <<
+            "Target DSP: " << result.target_dsp_freq <<
+            "Actual DSP: " << result.actual_dsp_freq;
+
+        if (result.clipped_rf_freq != result.target_rf_freq) {
+            etiLog.level(warn) <<
+                "OutputUHD: clipped RF frequency " << std::fixed <<
+                " different from target";
+        }
+    }
+    else {
+        //set the centre frequency
+        etiLog.log(info, "OutputUHD:Setting freq to %f...\n", myConf.frequency);
+        myUsrp->set_tx_freq(myConf.frequency);
+    }
     myConf.frequency = myUsrp->get_tx_freq();
     MDEBUG("OutputUHD:Actual frequency: %f\n", myConf.frequency);
 
diff --git a/src/OutputUHD.h b/src/OutputUHD.h
index e477e47..cbf159f 100644
--- a/src/OutputUHD.h
+++ b/src/OutputUHD.h
@@ -182,6 +182,7 @@ struct OutputUHDConfig {
     long masterClockRate = 32768000;
     unsigned sampleRate = 2048000;
     double frequency = 0.0;
+    double lo_offset = 0.0;
     double txgain = 0.0;
     bool enableSync = false;
     bool muteNoTimestamps = false;
-- 
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