Merge pull request #2 from fourstix/issue_1

Updated tune_cap property to take/resturn pf values

Author: fourstix

examples/example3_tune_antenna_i2c.py

@@ -56,12 +56,12 @@
 # 16 by default but can be 32, 64, or 128, depending on what value you set.
 print ('Division Ratio is set to: ', str(lightning.division_ratio))
 
-# Here you give a value of 0-15, which increases the capacitance on
-# the RLC circuit in steps of 8pF, up to 120pF. For example giving a
-# paramater of 2: 2 * 8pF = 16pF. # The change in frequency is very modest.
-# At 15 (max - 120pF), the frequency is around 490kHz down from 512kHz.
-# The equation for calculating frequency in an RLC circuit is:
-# f = 1/(2pi*sqrt(LC)). To change the capacitance, uncomment the line below.
+# Here you can set a value of 0-120, which increases the capacitance on
+# the RLC circuit in steps of 8pF, up to 120pF. The change in frequency is
+# very modest. At 15 (max - 120pF), the frequency is around 490kHz down from
+# 512kHz. The equation for calculating frequency in an RLC circuit is:
+# f = 1/(2pi*sqrt(LC))
+# To change the capacitance, uncomment the line below.
 # lightning.tune_cap = 0
 
 # When reading the internal capcitor value, it will return the value in pF.

examples/example3_tune_antenna_spi.py

@@ -60,12 +60,12 @@
 # 16 by default but can be 32, 64, or 128, depending on what value you set.
 print ('Division Ratio is set to: ', str(lightning.division_ratio))
 
-# Here you give a value of 0-15, which increases the capacitance on
-# the RLC circuit in steps of 8pF, up to 120pF. For example giving a
-# paramater of 2: 2 * 8pF = 16pF. # The change in frequency is very modest.
-# At 15 (max - 120pF), the frequency is around 490kHz down from 512kHz.
-# The equation for calculating frequency in an RLC circuit is:
-# f = 1/(2pi*sqrt(LC)). To change the capacitance, uncomment the line below.
+# Here you can set a value of 0-120, which increases the capacitance on
+# the RLC circuit in steps of 8pF, up to 120pF. The change in frequency is
+# very modest. At 15 (max - 120pF), the frequency is around 490kHz down from
+# 512kHz. The equation for calculating frequency in an RLC circuit is:
+# f = 1/(2pi*sqrt(LC))
+# To change the capacitance, uncomment the line below.
 # lightning.tune_cap = 0
 
 # When reading the internal capcitor value, it will return the value in pF.

sparkfun_qwiicas3935.py

@@ -486,9 +486,8 @@ def division_ratio(self, value):
 
     @property
     def tune_cap(self):
-        """This setting will return the capacitance of the internal capacitors. It will
-        return a value from one to 15 multiplied by the 8pF steps of the internal
-        capacitance."""
+        """This setting will return the capacitance of the internal capacitor.
+         It will return a value from 0 to 120pF, in 8pF steps."""
         # REG0x08, bits [3:0], manufacturer default: 0.
 
         value = self._read_register(_FREQ_DISP_IRQ)
@@ -500,13 +499,16 @@ def tune_cap(self):
     @tune_cap.setter
     def tune_cap(self, value):
         """This setting will add capacitance to the series RLC antenna on the
-        product. It's possible to add 0-120pF in steps of 8pF to the antenna.
-        The Tuning Cap value must be between 0 and 15."""
+        product. It's possible to add 0-120pF in steps of  8pF to the antenna.
+        The Tuning Cap value will be set between 0 and 120pF, in steps of 8pF.
+        If necessary, the input value is rounded down to the nearest 8pF."""
         # REG0x08, bits [3:0], manufacturer default: 0.
-        if value < 0 or value > 15:
-            raise ValueError('The Tuning Cap value must be between 0 and 15.')
+        # Divide down to integer 0 - 15, rounding down
+        reg_value = value // 8
+        if reg_value < 0 or reg_value > 15:
+            raise ValueError('The Tuning Cap value must be between 0 and 120pF.')
 
-        self._write_register_bits(_FREQ_DISP_IRQ, _CAP_MASK, value, 0)
+        self._write_register_bits(_FREQ_DISP_IRQ, _CAP_MASK, reg_value, 0)
 
     # abstract methods
     @abstractmethod