add raw frequency property; update docs

Author: CedarGroveStudios

README.rst

@@ -23,9 +23,9 @@ A CircuitPython driver for the AD9833 Programmable Waveform Generator.
 .. image:: https://github.com/CedarGroveStudios/CircuitPython_AD9833/blob/master/media/DSC05796_combo.jpg
 
 
-The AD9833 is a programmable waveform generator that produces sine, square, and triangular waveform output from 0 MHz to 12.5MHz with 28-bit resoluLon. The driver controls the waveform generator's frequency, phase, and waveform type.
+The AD9833 is a programmable waveform generator that produces sine, square, and triangular waveform output from 0 MHz to 12.5MHz with 28-bit resolution. The driver controls the waveform generator's frequency, phase, and waveform type.
 
-The Cedar Grove AD9833 Precision Waveform Generator and AD9833 ADSR Precision Waveform Generator FeatherWings provide all the support circuitry for the AD9833. The ADSR (Attack, Decay, Sustain, Release) version incorporates the AD5245 digital potenLometer to provide output amplitude control.
+The Cedar Grove AD9833 Precision Waveform Generator and AD9833 ADSR Precision Waveform Generator FeatherWings provide all the support circuitry for the AD9833. The ADSR (Attack, Decay, Sustain, Release) version incorporates the AD5245 digital potentiometer to provide output amplitude control.
 
 
 Dependencies

cedargrove_ad9833.py

@@ -55,9 +55,9 @@ def __init__(
         During initialization, the generator is reset and placed in the pause
         state.
 
-        :param int wave_freq: The 28-bit waveform frequency in Hz ranging from
-        0 to 2 ** 28. Practical maximum is 12.5MHz (one-half the master clock
-          frequency). Defaults to 440.
+        :param float wave_freq: The floating point waveform frequency in Hz
+        ranging from 0.09 to 12.5MHz (one-half the master clock frequency).
+        Defaults to 440. Resolution is approximately 0.09Hz.
         :param int wave_phase: The waveform phase offset in 2π Rad // 4096.
           Defaults to 0.
         :param str wave_type: The "sine", "triangle", or "square" wave shape.
@@ -92,7 +92,9 @@ def __init__(
 
     @property
     def wave_freq(self):
-        """The wave generator output frequency value."""
+        """The frequency output of the wave generator. The wave_freq value can
+        differ slightly from the wave generator’s output frequency due to the
+        internal conversion needed for loading the DAC counter register."""
         return self._wave_freq
 
     @wave_freq.setter
@@ -104,6 +106,16 @@ def wave_freq(self, new_wave_freq=440):
         self._wave_freq = min(self._wave_freq, self._m_clock // 2)
         self._update_freq_register(self._wave_freq)
 
+    @property
+    def raw_wave_freq(self):
+        """The frequency output of the wave generator as derived from the
+        DAC counter register (FREQREG) value. The raw frequency is based on the
+        25Mhz master clock and the 28-bit DAC counter register. The raw wave
+        value can differ slightly from wave_freq due to the internal conversion
+        needed for loading the DAC counter register."""
+        freq_word = int(round(float(self._wave_freq * pow(2, 28)) / self._m_clock))
+        return freq_word * (self._m_clock / pow(2, 28))
+
     @property
     def wave_phase(self):
         """The wave generator integer output phase value."""
@@ -129,7 +141,7 @@ def wave_type(self, new_wave_type="sine"):
         :param str new_wave_type: The waveform type. Defaults to 'sine'."""
         self._wave_type = new_wave_type
         if self._wave_type not in ("triangle", "square", "sine"):
-            # Default to sine in type isn't valid
+            # Default to sine if type isn't valid
             self._wave_type = "sine"
         self._update_control_register()