RTL-SDR: updated documentation and widgets tool tips

plugins/samplesource/rtlsdr/readme.md

@@ -2,7 +2,7 @@
 
 <h2>Introduction</h2>
 
-This input sample source plugin gets its samples from a [RTLSDR device](http://www.rtl-sdr.com/). 
+This input sample source plugin gets its samples from a [RTLSDR device](http://www.rtl-sdr.com/).
 
 <h2>Build</h2>
 
@@ -24,19 +24,21 @@ This is the center frequency of reception in kHz.
 
 <h4>1.2: Start/Stop</h4>
 
-Device start / stop button. 
+Device start / stop button.
 
   - Blue triangle icon: device is ready and can be started
   - Green square icon: device is running and can be stopped
   - Magenta (or pink) square icon: an error occurred. In the case the device was accidentally disconnected you may click on the icon, plug back in and start again.
-  
+
 <h4>1.3: Record</h4>
 
 Record baseband I/Q stream toggle button
 
-<h4>1.4: Stream sample rate</h4>
+<h4>1.4: Device or Baseband sample rate</h4>
 
-Baseband I/Q sample rate in kS/s. This is the device sample rate (4) divided by the decimation factor (6). 
+In device sample rate input mode (7) this is the baseband I/Q sample rate in kS/s. This is the device sample rate (8) divided by the decimation factor (9).
+
+In baseband sample rate input mode (7) this is the device I/Q sample rate in kS/s. This is the baseband sample rate (8) multiplied bu the decimation factor (9)
 
 <h3>2: Local Oscillator correction</h3>
 
@@ -48,19 +50,19 @@ These buttons control the local DSP auto correction options:
 
   - **DC**: auto remove DC component
   - **IQ**: auto make I/Q balance. The DC correction must be enabled for this to be effective.
-  
+
 <h3>4: Decimated bandpass center frequency position relative the RTL-SDR center frequency</h3>
 
   - **Cen**: the decimation operation takes place around the RTL-SDR center frequency Fs
-  - **Inf**: the decimation operation takes place around Fs - Fc. 
+  - **Inf**: the decimation operation takes place around Fs - Fc.
   - **Sup**: the decimation operation takes place around Fs + Fc.
-  
-With SR as the sample rate before decimation Fc is calculated as: 
+
+With SR as the sample rate before decimation Fc is calculated as:
 
   - if decimation n is 4 or lower:  Fc = SR/2^(log2(n)-1). The device center frequency is on the side of the baseband. You need a RF filter bandwidth at least twice the baseband.
   - if decimation n is 8 or higher: Fc = SR/n. The device center frequency is half the baseband away from the side of the baseband. You need a RF filter bandwidth at least 3 times the baseband.
 
-<h3>4a: Transverter mode open dialog</h3>
+<h3>5: Transverter mode open dialog</h3>
 
 This button opens a dialog to set the transverter mode frequency translation options:
 
@@ -68,11 +70,11 @@ This button opens a dialog to set the transverter mode frequency translation opt
 
 Note that if you mouse over the button a tooltip appears that displays the translating frequency and if translation is enabled or disabled. When the frequency translation is enabled the button is lit.
 
-<h4>4a.1: Translating frequency</h4>
+<h4>5.1: Translating frequency</h4>
 
 You can set the translating frequency in Hz with this dial. Use the wheels to adjust the sample rate. Left click on a digit sets the cursor position at this digit. Right click on a digit sets all digits on the right to zero. This effectively floors value at the digit position. Wheels are moved with the mousewheel while pointing at the wheel or by selecting the wheel with the left mouse click and using the keyboard arrows. Pressing shift simultaneously moves digit by 5 and pressing control moves it by 2.
 
-The frequency set in the device is the frequency on the main dial (1) minus this frequency. Thus it is positive for down converters and negative for up converters. 
+The frequency set in the device is the frequency on the main dial (1) minus this frequency. Thus it is positive for down converters and negative for up converters.
 
 For example with the DX Patrol that has a mixer at 120 MHz for HF operation you would set the value to -120,000,000 Hz so that if the main dial frequency is set at 7,130 kHz the RTLSDR of the DX Patrol will be set to 127.130 MHz.
 
@@ -82,43 +84,54 @@ For bands even higher in the frequency spectrum the GHz digits are not really si
 
 The Hz precision allows a fine tuning of the transverter LO offset
 
-<h4>4a.2: Translating frequency enable/disable</h4>
+<h4>5.2: Translating frequency enable/disable</h4>
 
 Use this toggle button to activate or deactivate the frequency translation
 
-<h4>4a.3: Confirmation buttons</h4>
+<h4>5.3: Confirmation buttons</h4>
 
-Use these buttons to confirm ("OK") or dismiss ("Cancel") your changes. 
+Use these buttons to confirm ("OK") or dismiss ("Cancel") your changes.
 
-<h3>5: Toggle low/high sample rate range</h3>
+<h3>6: Toggle low/high sample rate range</h3>
 
 When button is on the sample rate can vary from 230 kS/s to 300 kS/s
 When button is off the sample rate can vary from 950 kS/s to 2400 kS/s
 
-<h3>6: Device sample rate</h3>
+<h3>7: Device sample rate / Baseband sample rate input toggle</h3>
 
-This is the device sample rate in samples per second (S/s).
+Use this toggle button to switch the sample rate input next (8) between device sample rate and baseband sample rate input. The button shows the current mode:
+
+  - **SR**: device sample rate input mode. The baseband sample rate (1.4) is the device sample rate (8) divided by the decimation factor (9).
+  - **BB**: baseband sample rate input mode. The device sample rate (1.4) is the baseband sample rate (8) multiplied by the decimation factor (9).
+
+<h3>8: Sample rate</h3>
+
+This is the device sample rate or baseband sample rate in samples per second (S/s). The control (7) is used to switch between the two input modes.
+
+The limits are adjusted automatically. In baseband input mode the limits are driven by the decimation factor (9). You may need to increase this decimation factor to be able to reach lower values.
 
 Use the wheels to adjust the sample rate. Left click on a digit sets the cursor position at this digit. Right click on a digit sets all digits on the right to zero. This effectively floors value at the digit position. Wheels are moved with the mousewheel while pointing at the wheel or by selecting the wheel with the left mouse click and using the keyboard arrows. Pressing shift simultaneously moves digit by 5 and pressing control moves it by 2.
 
-<h3>7: Decimation factor</h3>
+<h3>9: Decimation factor</h3>
 
 The I/Q stream from the RTLSDR ADC is downsampled by a power of two before being sent to the passband. Possible values are increasing powers of two: 1 (no decimation), 2, 4, 8, 16, 32, 64.
 
-<h3>8: Direct sampling mode</h3>
+<h3>10: Direct sampling mode</h3>
 
 Use this checkbox to activate the special RTLSDR direct sampling. This can be used to tune to HF frequencies.
 
-<h3>9: Offset tuning</h3>
+<h3>11: Offset tuning</h3>
 
 This controls the offset tuning. Some RF frontends like the obsolete E4000 implement this feature and it can seriously reduce the central DC peak without digital correction. This does not work for the R820T and R820T2 that are very popular on which it will produce no effect. However these RF frontends exhibit a central DC peak much smaller than on the E4000 and can be easly corrected digitally via control (3).
 
-<h3>10: RF bandwidth</h3>
+<h3>12: RF bandwidth</h3>
 
 This controls the tuner filter bandwidth and can be varied from 350 kHz to 8 MHz. In practice depending on the value this appears to be larger and the filter center is slightly offset above the center frequency. This can still be very useful to eliminate or attenuate large signals outside the device to host I/Q stream passband.
 
-<h3>11: RF gain and AGC</h2>
+<h3>13: RF gain</h2>
 
 The slider sets RF gain in dB. The values are defined in the RTLSDR device and generally are: 0.0, 0.9, 1.4, 2.7, 3.7, 7.7, 8.7, 12.5, 14.4, 15.7, 16.6, 19.7, 20.7, 22.9, 25.4, 28.0, 29.7, 32.8, 33.8, 36.4, 37.2, 38.6, 40.2, 42.1, 43.4, 43.9, 44.5, 48.0, 49.6
 
-The AGC checkbox can be used to switch on or off the RTL2838 AGC. This is independent of the gain setting as this AGC acts after the gain block. 
+<h3>14: Automatic Gain Control (AGC)</h3>
+
+The AGC checkbox can be used to switch on or off the RTL2838 AGC. This is independent of the gain setting as this AGC acts after the gain block.

plugins/samplesource/rtlsdr/rtlsdrgui.cpp

@@ -251,11 +251,12 @@ void RTLSDRGui::displayGains()
 
 void RTLSDRGui::displaySampleRate()
 {
-    ui->sampleRateMode->setStyleSheet("QToolButton { background:rgb(79,79,79); }");
     ui->sampleRate->blockSignals(true);
+    displayFcTooltip();
 
     if (m_sampleRateMode)
     {
+        ui->sampleRateMode->setStyleSheet("QToolButton { background:rgb(60,60,60); }");
         ui->sampleRateMode->setText("SR");
 
         if (m_settings.m_lowSampleRate) {
@@ -272,6 +273,7 @@ void RTLSDRGui::displaySampleRate()
     }
     else
     {
+        ui->sampleRateMode->setStyleSheet("QToolButton { background:rgb(50,50,50); }");
         ui->sampleRateMode->setText("BB");
 
         if (m_settings.m_lowSampleRate) {
@@ -289,6 +291,17 @@ void RTLSDRGui::displaySampleRate()
     ui->sampleRate->blockSignals(false);
 }
 
+void RTLSDRGui::displayFcTooltip()
+{
+    int32_t fShift = DeviceSampleSource::calculateFrequencyShift(
+        m_settings.m_log2Decim,
+        (DeviceSampleSource::fcPos_t) m_settings.m_fcPos,
+        m_settings.m_devSampleRate,
+        DeviceSampleSource::FrequencyShiftScheme::FSHIFT_STD
+    );
+    ui->fcPos->setToolTip(tr("Relative position of device center frequency: %1 kHz").arg(QString::number(fShift / 1000.0f, 'g', 5)));
+}
+
 void RTLSDRGui::displaySettings()
 {
     ui->transverter->setDeltaFrequency(m_settings.m_transverterDeltaFrequency);
@@ -343,16 +356,9 @@ void RTLSDRGui::on_decim_currentIndexChanged(int index)
 
 void RTLSDRGui::on_fcPos_currentIndexChanged(int index)
 {
-	if (index == 0) {
-		m_settings.m_fcPos = RTLSDRSettings::FC_POS_INFRA;
-		sendSettings();
-	} else if (index == 1) {
-		m_settings.m_fcPos = RTLSDRSettings::FC_POS_SUPRA;
-		sendSettings();
-	} else if (index == 2) {
-		m_settings.m_fcPos = RTLSDRSettings::FC_POS_CENTER;
-		sendSettings();
-	}
+    m_settings.m_fcPos = (RTLSDRSettings::fcPos_t) (index < 0 ? 0 : index > 2 ? 2 : index);
+    displayFcTooltip();
+    sendSettings();
 }
 
 void RTLSDRGui::on_ppm_valueChanged(int value)
@@ -501,6 +507,7 @@ void RTLSDRGui::on_sampleRate_changed(quint64 value)
         m_settings.m_devSampleRate = value * (1 << m_settings.m_log2Decim);
     }
 
+    displayFcTooltip();
     sendSettings();
 }
 

plugins/samplesource/rtlsdr/rtlsdrgui.h

@@ -70,6 +70,7 @@ private:
 
 	void displayGains();
     void displaySampleRate();
+    void displayFcTooltip();
 	void displaySettings();
 	void sendSettings();
 	void updateSampleRateAndFrequency();

plugins/samplesource/rtlsdr/rtlsdrgui.ui

@@ -146,7 +146,7 @@
         <enum>Qt::StrongFocus</enum>
        </property>
        <property name="toolTip">
-        <string>Tuner center frequency in kHz</string>
+        <string>Center frequency of reception in kHz</string>
        </property>
       </widget>
      </item>
@@ -362,7 +362,7 @@
         </size>
        </property>
        <property name="toolTip">
-        <string>Toggle between device to host and base band sample rate input</string>
+        <string>Toggle between device to host (SR) and base band (BB) sample rate input</string>
        </property>
        <property name="text">
         <string>SR</string>