From fd4d2bb64fcbbce1392754af2df0c47186a1954a Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Thu, 10 May 2018 11:47:13 +0200
Subject: [PATCH] Common static function to calculate device center frequency
 from all contributing parameters

---
 sdrbase/dsp/devicesamplesource.cpp | 43 ++++++++++++++++++++++++++++++
 sdrbase/dsp/devicesamplesource.h   | 14 ++++++++++
 2 files changed, 57 insertions(+)

diff --git a/sdrbase/dsp/devicesamplesource.cpp b/sdrbase/dsp/devicesamplesource.cpp
index 4295d2f3b..bc2e8a963 100644
--- a/sdrbase/dsp/devicesamplesource.cpp
+++ b/sdrbase/dsp/devicesamplesource.cpp
@@ -15,6 +15,7 @@
 // along with this program. If not, see <http://www.gnu.org/licenses/>.          //
 ///////////////////////////////////////////////////////////////////////////////////
 
+#include <QDebug>
 #include <dsp/devicesamplesource.h>
 
 DeviceSampleSource::DeviceSampleSource() :
@@ -39,3 +40,45 @@ void DeviceSampleSource::handleInputMessages()
 		}
 	}
 }
+
+qint64 DeviceSampleSource::calculateDeviceCenterFrequency(
+            quint64 centerFrequency,
+            qint64 transverterDeltaFrequency,
+            int log2Decim,
+            fcPos_t fcPos,
+            quint32 devSampleRate,
+            bool transverterMode)
+{
+    qint64 deviceCenterFrequency = centerFrequency;
+    deviceCenterFrequency -= transverterMode ? transverterDeltaFrequency : 0;
+    deviceCenterFrequency = deviceCenterFrequency < 0 ? 0 : deviceCenterFrequency;
+    qint64 f_img = deviceCenterFrequency;
+
+    if ((log2Decim == 0) || (fcPos == FC_POS_CENTER))
+    {
+        f_img = deviceCenterFrequency;
+    }
+    else
+    {
+        if (fcPos == FC_POS_INFRA)
+        {
+            deviceCenterFrequency += (devSampleRate / 4);
+            f_img = deviceCenterFrequency + devSampleRate/2;
+        }
+        else if (fcPos == FC_POS_SUPRA)
+        {
+            deviceCenterFrequency -= (devSampleRate / 4);
+            f_img = deviceCenterFrequency - devSampleRate/2;
+        }
+    }
+
+    qDebug() << "DeviceSampleSource::calculateDeviceCenterFrequency:"
+            << " desired center freq: " << centerFrequency << " Hz"
+            << " device center freq: " << deviceCenterFrequency << " Hz"
+            << " device sample rate: " << devSampleRate << "S/s"
+            << " Actual sample rate: " << devSampleRate/(1<<log2Decim) << "S/s"
+            << " center freq position code: " << fcPos
+            << " image frequency: " << f_img << "Hz";
+
+    return deviceCenterFrequency;
+}
diff --git a/sdrbase/dsp/devicesamplesource.h b/sdrbase/dsp/devicesamplesource.h
index 8ee7604ba..776ed7f00 100644
--- a/sdrbase/dsp/devicesamplesource.h
+++ b/sdrbase/dsp/devicesamplesource.h
@@ -35,6 +35,12 @@ namespace SWGSDRangel
 class SDRBASE_API DeviceSampleSource : public QObject {
 	Q_OBJECT
 public:
+    typedef enum {
+        FC_POS_INFRA = 0,
+        FC_POS_SUPRA,
+        FC_POS_CENTER
+    } fcPos_t;
+
 	DeviceSampleSource();
 	virtual ~DeviceSampleSource();
 	virtual void destroy() = 0;
@@ -80,6 +86,14 @@ public:
 	MessageQueue *getMessageQueueToGUI() { return m_guiMessageQueue; }
     SampleSinkFifo* getSampleFifo() { return &m_sampleFifo; }
 
+    static qint64 calculateDeviceCenterFrequency(
+            quint64 centerFrequency,
+            qint64 transverterDeltaFrequency,
+            int log2Decim,
+            fcPos_t fcPos,
+            quint32 devSampleRate,
+            bool transverterMode = false);
+
 protected slots:
 	void handleInputMessages();