1 files changed, 52 insertions, 1 deletions

diff --git a/include/usrp_uhd/utils.hpp b/include/usrp_uhd/utils.hpp
index c1b2bad5c..ef2362453 100644
--- a/include/usrp_uhd/utils.hpp
+++ b/include/usrp_uhd/utils.hpp
@@ -2,6 +2,7 @@
 // Copyright 2010 Ettus Research LLC
 //
 
+#include <usrp_uhd/wax.hpp>
 #include <boost/foreach.hpp>
 #include <boost/format.hpp>
 #include <boost/function.hpp>
@@ -25,6 +26,56 @@ std::vector<Key> get_map_keys(const std::map<Key, T> &m){
     return v;
 }
 
+template<typename T> T signum(T n){
+    if (n < 0) return -1;
+    if (n > 0) return 1;
+    return 0;
+}
+
+inline void tune(
+    freq_t target_freq,
+    freq_t lo_offset,
+    wax::proxy subdev_freq_proxy,
+    bool subdev_quadrature,
+    bool subdev_spectrum_inverted,
+    bool subdev_is_tx,
+    wax::proxy dsp_freq_proxy,
+    freq_t dsp_sample_rate
+){
+    // Ask the d'board to tune as closely as it can to target_freq+lo_offset
+    subdev_freq_proxy = target_freq + lo_offset;
+    freq_t inter_freq = wax::cast<freq_t>(subdev_freq_proxy);
+
+    // Calculate the DDC setting that will downconvert the baseband from the
+    // daughterboard to our target frequency.
+    freq_t delta_freq = target_freq - inter_freq;
+    int delta_sign = signum(delta_freq);
+    delta_freq *= delta_sign;
+    delta_freq = fmod(delta_freq, dsp_sample_rate);
+    bool inverted = delta_freq > dsp_sample_rate/2.0;
+    freq_t dxc_freq = inverted? (delta_freq - dsp_sample_rate) : (-delta_freq);
+    dxc_freq *= delta_sign;
+
+    // If the spectrum is inverted, and the daughterboard doesn't do
+    // quadrature downconversion, we can fix the inversion by flipping the
+    // sign of the dxc_freq...  (This only happens using the basic_rx board)
+    if (subdev_spectrum_inverted){
+        inverted = not inverted;
+    }
+    if (inverted and not subdev_quadrature){
+        dxc_freq = -dxc_freq;
+        inverted = not inverted;
+    }
+    if (subdev_is_tx){
+        dxc_freq = -dxc_freq;	// down conversion versus up conversion
+    }
+
+    dsp_freq_proxy = dxc_freq;
+    //freq_t actual_dxc_freq = wax::cast<freq_t>(dsp_freq_proxy);
+
+    //return some kind of tune result tuple/struct
+}
+
 } //namespace usrp_uhd
 
 /*!
@@ -57,7 +108,7 @@ namespace std{
         return last != std::find(first, last, elem);
     }
 
-    template <class T>
+    template<class T>
     T sum(const T &a, const T &b){
         return a + b;
     }