hackrf: implement full control for RF/IF/BB gain stages

the following named gain stages are available:

RF: MGA-81563, switchable 0 or 14dB
IF: MAX2837 LNA, 0 to 40dB in 8dB steps
BB: MAX2837 VGA, 0 to 62dB in 2dB steps

7 files changed, 339 insertions, 234 deletions

diff --git a/grc/gen_osmosdr_blocks.py b/grc/gen_osmosdr_blocks.py
index 0cd5ffe..76231aa 100644
--- a/grc/gen_osmosdr_blocks.py
+++ b/grc/gen_osmosdr_blocks.py
@@ -21,12 +21,12 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 MAIN_TMPL = """\
 <?xml version="1.0"?>
 <block>
-	<name>$(title) $sourk.title()</name>
-	<key>$(prefix)_$(sourk)_c</key>
-	<category>Sources</category>
-	<throttle>1</throttle>
-	<import>import osmosdr</import>
-	<make>osmosdr.$(sourk)_c( args="nchan=" + str(\$nchan) + " " + \$args )
+  <name>$(title) $sourk.title()</name>
+  <key>$(prefix)_$(sourk)_c</key>
+  <category>Sources</category>
+  <throttle>1</throttle>
+  <import>import osmosdr</import>
+  <make>osmosdr.$(sourk)_c( args="nchan=" + str(\$nchan) + " " + \$args )
 self.\$(id).set_sample_rate(\$sample_rate)
 #for $n in range($max_nchan)
 \#if \$nchan() > $n
@@ -36,72 +36,74 @@ self.\$(id).set_iq_balance_mode(\$iq_balance_mode$(n), $n)
 self.\$(id).set_gain_mode(\$gain_mode$(n), $n)
 self.\$(id).set_gain(\$gain$(n), $n)
 self.\$(id).set_if_gain(\$if_gain$(n), $n)
+self.\$(id).set_bb_gain(\$bb_gain$(n), $n)
 \#if \$ant$(n)()
 self.\$(id).set_antenna(\$ant$(n), $n)
 \#end if
 \#end if
 #end for
-	</make>
-	<callback>set_sample_rate(\$sample_rate)</callback>
-	#for $n in range($max_nchan)
-	<callback>set_center_freq(\$freq$(n), $n)</callback>
-	<callback>set_freq_corr(\$corr$(n), $n)</callback>
-	<callback>set_iq_balance_mode(\$iq_balance_mode$(n), $n)</callback>
-	<callback>set_gain_mode(\$gain_mode$(n), $n)</callback>
-	<callback>set_gain(\$gain$(n), $n)</callback>
-	<callback>set_if_gain(\$if_gain$(n), $n)</callback>
-	<callback>set_antenna(\$ant$(n), $n)</callback>
-	#end for
-	<param>
-		<name>$(dir.title())put Type</name>
-		<key>type</key>
-		<type>enum</type>
-		<option>
-			<name>Complex float32</name>
-			<key>fc32</key>
-			<opt>type:fc32</opt>
-		</option>
-	</param>
-	<param>
-		<name>Device Arguments</name>
-		<key>args</key>
-		<value></value>
-		<type>string</type>
-		<hide>
-			\#if \$args()
-				none
-			\#else
-				part
-			\#end if
-		</hide>
-	</param>
-	<param>
-		<name>Num Channels</name>
-		<key>nchan</key>
-		<value>1</value>
-		<type>int</type>
-		#for $n in range(1, $max_nchan+1)
-		<option>
-			<name>$(n)</name>
-			<key>$n</key>
-		</option>
-		#end for
-	</param>
-	<param>
-		<name>Sample Rate (sps)</name>
-		<key>sample_rate</key>
-		<value>samp_rate</value>
-		<type>real</type>
-	</param>
-	$params
-	<check>$max_nchan >= \$nchan</check>
-	<check>\$nchan > 0</check>
-	<$sourk>
-		<name>$dir</name>
-		<type>\$type.type</type>
-		<nports>\$nchan</nports>
-	</$sourk>
-	<doc>
+  </make>
+  <callback>set_sample_rate(\$sample_rate)</callback>
+  #for $n in range($max_nchan)
+  <callback>set_center_freq(\$freq$(n), $n)</callback>
+  <callback>set_freq_corr(\$corr$(n), $n)</callback>
+  <callback>set_iq_balance_mode(\$iq_balance_mode$(n), $n)</callback>
+  <callback>set_gain_mode(\$gain_mode$(n), $n)</callback>
+  <callback>set_gain(\$gain$(n), $n)</callback>
+  <callback>set_if_gain(\$if_gain$(n), $n)</callback>
+  <callback>set_bb_gain(\$bb_gain$(n), $n)</callback>
+  <callback>set_antenna(\$ant$(n), $n)</callback>
+  #end for
+  <param>
+    <name>$(dir.title())put Type</name>
+    <key>type</key>
+    <type>enum</type>
+    <option>
+      <name>Complex float32</name>
+      <key>fc32</key>
+      <opt>type:fc32</opt>
+    </option>
+  </param>
+  <param>
+    <name>Device Arguments</name>
+    <key>args</key>
+    <value></value>
+    <type>string</type>
+    <hide>
+      \#if \$args()
+        none
+      \#else
+        part
+      \#end if
+    </hide>
+  </param>
+  <param>
+    <name>Num Channels</name>
+    <key>nchan</key>
+    <value>1</value>
+    <type>int</type>
+    #for $n in range(1, $max_nchan+1)
+    <option>
+      <name>$(n)</name>
+      <key>$n</key>
+    </option>
+    #end for
+  </param>
+  <param>
+    <name>Sample Rate (sps)</name>
+    <key>sample_rate</key>
+    <value>samp_rate</value>
+    <type>real</type>
+  </param>
+  $params
+  <check>$max_nchan >= \$nchan</check>
+  <check>\$nchan > 0</check>
+  <$sourk>
+    <name>$dir</name>
+    <type>\$type.type</type>
+    <nports>\$nchan</nports>
+  </$sourk>
+  <doc>
 The OsmoSDR $sourk.title() block:
 
 While primarily being developed for the OsmoSDR hardware, this block as well supports:
@@ -155,23 +157,28 @@ The frequency correction factor in parts per million (ppm). Set to 0 if unknown.
 
 IQ Balance Mode:
 Controls the behavior of software IQ imbalance corrrection.
-  Off: Disable correction algorithm (pass through)
-  Manual: Keep last estimated correction when switched from Automatic to Manual
-  Automatic: Find the best solution to compensate for image signals.
+  Off: Disable correction algorithm (pass through).
+  Manual: Keep last estimated correction when switched from Automatic to Manual.
+  Automatic: Periodicallly find the best solution to compensate for image signals.
 
 This functionality depends on http://cgit.osmocom.org/cgit/gr-iqbal/
 
 Gain Mode:
 Chooses between the manual (default) and automatic gain mode where appropriate.
-Currently, only rtlsdr devices support automatic gain mode.
+To allow manual control of RF/IF/BB gain stages, manual gain mode must be configured.
+Currently, only RTL-SDR devices support automatic gain mode.
 
 RF Gain:
-Overall RF gain of the receiving device. For the new gain value to be applied, the manual gain mode must be enabled first.
+Overall RF gain of the receiving device.
 
 IF Gain:
-Overall IF gain of the receiving device. For the new gain value to be applied, the manual gain mode must be enabled first.
+Overall intermediate frequency gain of the receiving device.
 This setting has only effect for RTL-SDR and OsmoSDR devices with E4000 tuners. Observations lead to a reasonable gain range from 15 to 30dB.
 
+BB Gain:
+Overall baseband gain of the receiving device.
+This setting has only effect for HackRF Jawbreaker. Observations lead to a reasonable gain range from 15 to 30dB.
+
 Antenna:
 For devices with only one antenna, this may be left blank.
 Otherwise, the user should specify one of the possible antenna choices.
@@ -180,125 +187,132 @@ See the OsmoSDR project page for more detailed documentation:
 http://sdr.osmocom.org/trac/
 http://sdr.osmocom.org/trac/wiki/rtl-sdr
 http://sdr.osmocom.org/trac/wiki/GrOsmoSDR
-	</doc>
+  </doc>
 </block>
 """
 
 PARAMS_TMPL = """
-	<param>
-		<name>Ch$(n): Frequency (Hz)</name>
-		<key>freq$(n)</key>
-		<value>100e6</value>
-		<type>real</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-	</param>
-	<param>
-	<name>Ch$(n): Freq. Corr. (ppm)</name>
-		<key>corr$(n)</key>
-		<value>0</value>
-		<type>real</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-	</param>
-	<param>
-		<name>Ch$(n): IQ Balance Mode</name>
-		<key>iq_balance_mode$(n)</key>
-		<value>0</value>
-		<type>int</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-		<option>
-			<name>Off</name>
-			<key>0</key>
-		</option>
-		<option>
-			<name>Manual</name>
-			<key>1</key>
-		</option>
-		<option>
-			<name>Automatic</name>
-			<key>2</key>
-		</option>
-	</param>
-	<param>
-		<name>Ch$(n): Gain Mode</name>
-		<key>gain_mode$(n)</key>
-		<value>0</value>
-		<type>int</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-		<option>
-			<name>Manual</name>
-			<key>0</key>
-		</option>
-		<option>
-			<name>Automatic</name>
-			<key>1</key>
-		</option>
-	</param>
-	<param>
-		<name>Ch$(n): RF Gain (dB)</name>
-		<key>gain$(n)</key>
-		<value>10</value>
-		<type>real</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-	</param>
-	<param>
-		<name>Ch$(n): IF Gain (dB)</name>
-		<key>if_gain$(n)</key>
-		<value>24</value>
-		<type>real</type>
-		<hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
-	</param>
-	<param>
-		<name>Ch$(n): Antenna</name>
-		<key>ant$(n)</key>
-		<value></value>
-		<type>string</type>
-		<hide>
-			\#if not \$nchan() > $n
-				all
-			\#elif \$ant$(n)()
-				none
-			\#else
-				part
-			\#end if
-		</hide>
-	</param>
+  <param>
+    <name>Ch$(n): Frequency (Hz)</name>
+    <key>freq$(n)</key>
+    <value>100e6</value>
+    <type>real</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+  </param>
+  <param>
+  <name>Ch$(n): Freq. Corr. (ppm)</name>
+    <key>corr$(n)</key>
+    <value>0</value>
+    <type>real</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+  </param>
+  <param>
+    <name>Ch$(n): IQ Balance Mode</name>
+    <key>iq_balance_mode$(n)</key>
+    <value>0</value>
+    <type>int</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+    <option>
+      <name>Off</name>
+      <key>0</key>
+    </option>
+    <option>
+      <name>Manual</name>
+      <key>1</key>
+    </option>
+    <option>
+      <name>Automatic</name>
+      <key>2</key>
+    </option>
+  </param>
+  <param>
+    <name>Ch$(n): Gain Mode</name>
+    <key>gain_mode$(n)</key>
+    <value>0</value>
+    <type>int</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+    <option>
+      <name>Manual</name>
+      <key>0</key>
+    </option>
+    <option>
+      <name>Automatic</name>
+      <key>1</key>
+    </option>
+  </param>
+  <param>
+    <name>Ch$(n): RF Gain (dB)</name>
+    <key>gain$(n)</key>
+    <value>10</value>
+    <type>real</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+  </param>
+  <param>
+    <name>Ch$(n): IF Gain (dB)</name>
+    <key>if_gain$(n)</key>
+    <value>20</value>
+    <type>real</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+  </param>
+  <param>
+    <name>Ch$(n): BB Gain (dB)</name>
+    <key>bb_gain$(n)</key>
+    <value>20</value>
+    <type>real</type>
+    <hide>\#if \$nchan() > $n then 'none' else 'all'#</hide>
+  </param>
+  <param>
+    <name>Ch$(n): Antenna</name>
+    <key>ant$(n)</key>
+    <value></value>
+    <type>string</type>
+    <hide>
+      \#if not \$nchan() > $n
+        all
+      \#elif \$ant$(n)()
+        none
+      \#else
+        part
+      \#end if
+    </hide>
+  </param>
 """
 
 def parse_tmpl(_tmpl, **kwargs):
-	from Cheetah import Template
-	return str(Template.Template(_tmpl, kwargs))
+  from Cheetah import Template
+  return str(Template.Template(_tmpl, kwargs))
 
 max_num_channels = 5
 
 import os.path
 
 if __name__ == '__main__':
-	import sys
-	for file in sys.argv[1:]:
-		head, tail = os.path.split(file)
-
-		if tail.startswith('rtlsdr'):
-			title = 'RTLSDR'
-			prefix = 'rtlsdr'
-		elif tail.startswith('osmosdr'):
-			title = 'OsmoSDR'
-			prefix = 'osmosdr'
-		else: raise Exception, 'file %s has wrong syntax!'%tail
-
-		if tail.endswith ('source_c.xml'):
-			sourk = 'source'
-			dir = 'out'
-		elif tail.endswith ('sink_c.xml'):
-			sourk = 'sink'
-			dir = 'in'
-		else: raise Exception, 'is %s a source or sink?'%file
-
-		params = ''.join([parse_tmpl(PARAMS_TMPL, n=n) for n in range(max_num_channels)])
-		open(file, 'w').write(parse_tmpl(MAIN_TMPL,
-			max_nchan=max_num_channels,
-			params=params,
-			title=title,
-			prefix=prefix,
-			sourk=sourk,
-			dir=dir,
-		))
+  import sys
+  for file in sys.argv[1:]:
+    head, tail = os.path.split(file)
+
+    if tail.startswith('rtlsdr'):
+      title = 'RTLSDR'
+      prefix = 'rtlsdr'
+    elif tail.startswith('osmosdr'):
+      title = 'OsmoSDR'
+      prefix = 'osmosdr'
+    else: raise Exception, 'file %s has wrong syntax!'%tail
+
+    if tail.endswith ('source_c.xml'):
+      sourk = 'source'
+      dir = 'out'
+    elif tail.endswith ('sink_c.xml'):
+      sourk = 'sink'
+      dir = 'in'
+    else: raise Exception, 'is %s a source or sink?'%file
+
+    params = ''.join([parse_tmpl(PARAMS_TMPL, n=n) for n in range(max_num_channels)])
+    open(file, 'w').write(parse_tmpl(MAIN_TMPL,
+      max_nchan=max_num_channels,
+      params=params,
+      title=title,
+      prefix=prefix,
+      sourk=sourk,
+      dir=dir,
+    ))
diff --git a/include/osmosdr/osmosdr_source_c.h b/include/osmosdr/osmosdr_source_c.h
index 453f592..dd4505c 100644
--- a/include/osmosdr/osmosdr_source_c.h
+++ b/include/osmosdr/osmosdr_source_c.h
@@ -208,6 +208,16 @@ public:
   virtual double set_if_gain( double gain, size_t chan = 0 ) = 0;
 
   /*!
+   * Set the BB gain for the underlying radio hardware.
+   * This function will automatically distribute the desired gain value over
+   * available BB gain stages in an appropriate way and return the actual value.
+   * \param gain the gain in dB
+   * \param chan the channel index 0 to N-1
+   * \return the actual gain in dB
+   */
+  virtual double set_bb_gain( double gain, size_t chan = 0 ) = 0;
+
+  /*!
    * Get the available antennas of the underlying radio hardware.
    * \param chan the channel index 0 to N-1
    * \return a vector of strings containing the names of available antennas
@@ -226,7 +236,7 @@ public:
   /*!
    * Get the actual underlying radio hardware antenna setting.
    * \param chan the channel index 0 to N-1
-   * \return antenna the actual antenna's name
+   * \return the actual antenna's name
    */
   virtual std::string get_antenna( size_t chan = 0 ) = 0;
 
diff --git a/lib/hackrf/hackrf_source_c.cc b/lib/hackrf/hackrf_source_c.cc
index 0ded9f3..5543ea0 100644
--- a/lib/hackrf/hackrf_source_c.cc
+++ b/lib/hackrf/hackrf_source_c.cc
@@ -83,7 +83,9 @@ hackrf_source_c::hackrf_source_c (const std::string &args)
     _center_freq(0),
     _freq_corr(0),
     _auto_gain(false),
-    _if_gain(0),
+    _amp_gain(0),
+    _lna_gain(0),
+    _vga_gain(0),
     _skipped(0)
 {
   int ret;
@@ -157,21 +159,17 @@ hackrf_source_c::hackrf_source_c (const std::string &args)
               << std::endl;
   }
 
-  ret = hackrf_sample_rate_set( _dev, 10000000 );
-  if (ret != HACKRF_SUCCESS)
-    throw std::runtime_error("Failed to set default samplerate.");
+  set_sample_rate( 5000000 );
 
-  ret = hackrf_set_amp_enable( _dev, 0 );
-  if (ret != HACKRF_SUCCESS)
-    throw std::runtime_error("Failed to disable the RX amplifier.");
+  set_gain( 0 ); /* disable AMP gain stage */
 
   hackrf_max2837_read( _dev, 8, &val );
   val |= 0x3; /* enable LNA & VGA control over SPI */
   hackrf_max2837_write( _dev, 8, val );
 
-  set_if_gain( 24 ); /* preset to a reasonable default (non-GRC use case) */
+  set_if_gain( 16 ); /* preset to a reasonable default (non-GRC use case) */
 
-  set_gain( 16 ); /* preset to a reasonable default (non-GRC use case) */
+  set_bb_gain( 20 ); /* preset to a reasonable default (non-GRC use case) */
 
   _buf = (unsigned short **) malloc(_buf_num * sizeof(unsigned short *));
 
@@ -365,7 +363,7 @@ double hackrf_source_c::set_sample_rate(double rate)
       _sample_rate = rate;
       set_bandwidth( rate );
     } else {
-      throw std::runtime_error( std::string( hackrf_error_name( (hackrf_error) ret ) ) );
+      throw std::runtime_error( std::string( __FUNCTION__ ) );
     }
   }
 
@@ -398,7 +396,7 @@ double hackrf_source_c::set_center_freq( double freq, size_t chan )
     if ( HACKRF_SUCCESS == ret ) {
       _center_freq = freq;
     } else {
-      throw std::runtime_error( std::string( hackrf_error_name( (hackrf_error) ret ) ) );
+      throw std::runtime_error( std::string( __FUNCTION__ ) );
     }
   }
 
@@ -428,28 +426,33 @@ std::vector<std::string> hackrf_source_c::get_gain_names( size_t chan )
 {
   std::vector< std::string > names;
 
-  names += "LNA";
+  names += "RF";
   names += "IF";
+  names += "BB";
 
   return names;
 }
 
 osmosdr::gain_range_t hackrf_source_c::get_gain_range( size_t chan )
 {
-  osmosdr::gain_range_t range;
-
-  range += osmosdr::range_t( 0, 40, 8 );
-
-  return range;
+  return get_gain_range( "RF", chan );
 }
 
 osmosdr::gain_range_t hackrf_source_c::get_gain_range( const std::string & name, size_t chan )
 {
+  if ( "RF" == name ) {
+    return osmosdr::gain_range_t( 0, 14, 14 );
+  }
+
   if ( "IF" == name ) {
+    return osmosdr::gain_range_t( 0, 40, 8 );
+  }
+
+  if ( "BB" == name ) {
     return osmosdr::gain_range_t( 0, 62, 2 );
   }
 
-  return get_gain_range( chan );
+  return osmosdr::gain_range_t();
 }
 
 bool hackrf_source_c::set_gain_mode( bool automatic, size_t chan )
@@ -466,56 +469,65 @@ bool hackrf_source_c::get_gain_mode( size_t chan )
 
 double hackrf_source_c::set_gain( double gain, size_t chan )
 {
-  osmosdr::gain_range_t rf_gains = get_gain_range( chan );
+  osmosdr::gain_range_t rf_gains = get_gain_range( "RF", chan );
 
   if (_dev) {
     double clip_gain = rf_gains.clip( gain, true );
-    double rel_gain = fabs( rf_gains.stop() - clip_gain );
 
     std::map<double, int> reg_vals;
     reg_vals[ 0 ] = 0;
-    reg_vals[ 8 ] = 4;
-    reg_vals[ 16 ] = 2;
-    reg_vals[ 24 ] = 6;
-    reg_vals[ 32 ] = 3;
-    reg_vals[ 40 ] = 7;
-
-    if ( reg_vals.count( rel_gain ) ) {
-      int value = reg_vals[ rel_gain ];
+    reg_vals[ 14 ] = 1;
 
-//      std::cerr << "lna gain: " << rel_gain << " value: " << value << std::endl;
-
-      uint16_t val;
-      hackrf_max2837_read( _dev, 1, &val );
-
-      val = (val & ~(7 << 2)) | ((value & 7) << 2);
-
-      if ( hackrf_max2837_write( _dev, 1, val ) == HACKRF_SUCCESS )
-        _gain = clip_gain;
+    if ( reg_vals.count( clip_gain ) ) {
+      int value = reg_vals[ clip_gain ];
+#if 0
+      std::cerr << "amp gain: " << gain
+                << " clip_gain: " << clip_gain
+                << " value: " << value
+                << std::endl;
+#endif
+      if ( hackrf_set_amp_enable( _dev, value ) == HACKRF_SUCCESS )
+        _amp_gain = clip_gain;
     }
   }
 
-  return get_gain( chan );
+  return _amp_gain;
 }
 
 double hackrf_source_c::set_gain( double gain, const std::string & name, size_t chan)
 {
+  if ( "RF" == name ) {
+    return set_gain( gain, chan );
+  }
+
   if ( "IF" == name ) {
     return set_if_gain( gain, chan );
   }
 
+  if ( "BB" == name ) {
+    return set_bb_gain( gain, chan );
+  }
+
   return set_gain( gain, chan );
 }
 
 double hackrf_source_c::get_gain( size_t chan )
 {
-  return _gain;
+  return _amp_gain;
 }
 
 double hackrf_source_c::get_gain( const std::string & name, size_t chan )
 {
+  if ( "RF" == name ) {
+    return get_gain( chan );
+  }
+
   if ( "IF" == name ) {
-    return _if_gain;
+    return _lna_gain;
+  }
+
+  if ( "BB" == name ) {
+    return _vga_gain;
   }
 
   return get_gain( chan );
@@ -523,7 +535,45 @@ double hackrf_source_c::get_gain( const std::string & name, size_t chan )
 
 double hackrf_source_c::set_if_gain(double gain, size_t chan)
 {
-  osmosdr::gain_range_t if_gains = get_gain_range( "IF", chan );
+  osmosdr::gain_range_t rf_gains = get_gain_range( "IF", chan );
+
+  if (_dev) {
+    double clip_gain = rf_gains.clip( gain, true );
+    double rel_gain = fabs( rf_gains.stop() - clip_gain );
+
+    std::map<double, int> reg_vals;
+    reg_vals[ 0 ] = 0;
+    reg_vals[ 8 ] = 4;
+    reg_vals[ 16 ] = 2;
+    reg_vals[ 24 ] = 6;
+    reg_vals[ 32 ] = 3;
+    reg_vals[ 40 ] = 7;
+
+    if ( reg_vals.count( rel_gain ) ) {
+      int value = reg_vals[ rel_gain ];
+#if 0
+      std::cerr << "lna gain: " << gain
+                << " clip_gain: " << clip_gain
+                << " rel_gain: " << rel_gain
+                << " value: " << value
+                << std::endl;
+#endif
+      uint16_t val;
+      hackrf_max2837_read( _dev, 1, &val );
+
+      val = (val & ~(7 << 2)) | ((value & 7) << 2);
+
+      if ( hackrf_max2837_write( _dev, 1, val ) == HACKRF_SUCCESS )
+        _lna_gain = clip_gain;
+    }
+  }
+
+  return _lna_gain;
+}
+
+double hackrf_source_c::set_bb_gain( double gain, size_t chan )
+{
+  osmosdr::gain_range_t if_gains = get_gain_range( "BB", chan );
 
   if (_dev) {
     double clip_gain = if_gains.clip( gain, true );
@@ -536,20 +586,24 @@ double hackrf_source_c::set_if_gain(double gain, size_t chan)
 
     if ( reg_vals.count( rel_gain ) ) {
       int value = reg_vals[ rel_gain ];
-
-//      std::cerr << "vga gain: " << rel_gain << " value: " << value << std::endl;
-
+#if 0
+      std::cerr << "vga gain: " << gain
+                << " clip_gain: " << clip_gain
+                << " rel_gain: " << rel_gain
+                << " value: " << value
+                << std::endl;
+#endif
       uint16_t val;
       hackrf_max2837_read( _dev, 5, &val );
 
       val = (val & ~0x1f) | (value & 0x1f);
 
       if ( hackrf_max2837_write( _dev, 5, val ) == HACKRF_SUCCESS )
-        _if_gain = clip_gain;
+        _vga_gain = clip_gain;
     }
   }
 
-  return gain;
+  return _vga_gain;
 }
 
 std::vector< std::string > hackrf_source_c::get_antennas( size_t chan )
@@ -586,7 +640,7 @@ void hackrf_source_c::set_bandwidth( double bandwidth, size_t chan )
     if ( HACKRF_SUCCESS == ret ) {
       _bandwidth = bw;
     } else {
-      throw std::runtime_error( std::string( hackrf_error_name( (hackrf_error) ret ) ) );
+      throw std::runtime_error( std::string( __FUNCTION__ ) );
     }
   }
 }
diff --git a/lib/hackrf/hackrf_source_c.h b/lib/hackrf/hackrf_source_c.h
index 8bdb0d3..ea14944 100644
--- a/lib/hackrf/hackrf_source_c.h
+++ b/lib/hackrf/hackrf_source_c.h
@@ -107,6 +107,7 @@ private:
   double get_gain( const std::string & name, size_t chan = 0 );
 
   double set_if_gain( double gain, size_t chan = 0 );
+  double set_bb_gain( double gain, size_t chan = 0 );
 
   std::vector< std::string > get_antennas( size_t chan = 0 );
   std::string set_antenna( const std::string & antenna, size_t chan = 0 );
@@ -145,8 +146,9 @@ private:
   double _center_freq;
   double _freq_corr;
   bool _auto_gain;
-  double _gain;
-  double _if_gain;
+  double _amp_gain;
+  double _lna_gain;
+  double _vga_gain;
   unsigned int _skipped;
   double _bandwidth;
 };
diff --git a/lib/osmosdr_source_c_impl.cc b/lib/osmosdr_source_c_impl.cc
index b5e34e4..fcac3cb 100644
--- a/lib/osmosdr_source_c_impl.cc
+++ b/lib/osmosdr_source_c_impl.cc
@@ -541,7 +541,7 @@ double osmosdr_source_c_impl::get_gain( const std::string & name, size_t chan )
   return 0;
 }
 
-double osmosdr_source_c_impl::set_if_gain(double gain, size_t chan)
+double osmosdr_source_c_impl::set_if_gain( double gain, size_t chan )
 {
   size_t channel = 0;
   BOOST_FOREACH( osmosdr_src_iface *dev, _devs )
@@ -555,6 +555,20 @@ double osmosdr_source_c_impl::set_if_gain(double gain, size_t chan)
   return 0;
 }
 
+double osmosdr_source_c_impl::set_bb_gain( double gain, size_t chan )
+{
+  size_t channel = 0;
+  BOOST_FOREACH( osmosdr_src_iface *dev, _devs )
+    for (size_t dev_chan = 0; dev_chan < dev->get_num_channels(); dev_chan++)
+      if ( chan == channel++ )
+        if ( _if_gain[ chan ] != gain ) {
+          _if_gain[ chan ] = gain;
+          return dev->set_bb_gain( gain, dev_chan );
+        }
+
+  return 0;
+}
+
 std::vector< std::string > osmosdr_source_c_impl::get_antennas( size_t chan )
 {
   size_t channel = 0;
diff --git a/lib/osmosdr_source_c_impl.h b/lib/osmosdr_source_c_impl.h
index 292ca90..92c8d38 100644
--- a/lib/osmosdr_source_c_impl.h
+++ b/lib/osmosdr_source_c_impl.h
@@ -57,6 +57,7 @@ public:
   double get_gain( const std::string & name, size_t chan = 0 );
 
   double set_if_gain( double gain, size_t chan = 0 );
+  double set_bb_gain( double gain, size_t chan = 0 );
 
   std::vector< std::string > get_antennas( size_t chan = 0 );
   std::string set_antenna( const std::string & antenna, size_t chan = 0 );
diff --git a/lib/osmosdr_src_iface.h b/lib/osmosdr_src_iface.h
index 8169b3a..6c149f9 100644
--- a/lib/osmosdr_src_iface.h
+++ b/lib/osmosdr_src_iface.h
@@ -186,6 +186,16 @@ public:
   virtual double set_if_gain( double gain, size_t chan = 0 ) { return 0; }
 
   /*!
+   * Set the BB gain for the underlying radio hardware.
+   * This function will automatically distribute the desired gain value over
+   * available BB gain stages in an appropriate way and return the actual value.
+   * \param gain the gain in dB
+   * \param chan the channel index 0 to N-1
+   * \return the actual gain in dB
+   */
+  virtual double set_bb_gain( double gain, size_t chan = 0 ) { return 0; }
+
+  /*!
    * Get the available antennas of the underlying radio hardware.
    * \param chan the channel index 0 to N-1
    * \return a vector of strings containing the names of available antennas
@@ -203,7 +213,7 @@ public:
   /*!
    * Get the actual underlying radio hardware antenna setting.
    * \param chan the channel index 0 to N-1
-   * \return antenna the actual antenna's name
+   * \return the actual antenna's name
    */
   virtual std::string get_antenna( size_t chan = 0 ) = 0;
 };