Fixed issue #15 with pwm acting three times as fast.

Author: Thomas Preston

CHANGELOG

@@ -1,6 +1,11 @@
 Change Log
 ==========
 
+v0.7.4
+------
+- Fixed a bug with io_pwm() running three times faster than it should.
+  Fixes #15.
+
 v0.7.3
 ------
 - Fixed a bug with colourtail timing issue in the firmware.

codebug_tether/core.py

@@ -170,7 +170,7 @@ def pwm_on(self, t2_prescale, full_period, on_period):
         """Turns on the PWM generator with the given settings.
 
         :param t2_prescale: One of T2_PS_1_1, T2_PS_1_4, T2_PS_1_16
-                            Scales down the 4MHz instruction clock by
+                            Scales down the 12MHz instruction clock by
                             1, 4 or 16.
         :param full_period: 8-bit value - which is scaled up to 10-bits
                             (<< 2) - to which timer 2 will count up to
@@ -180,7 +180,7 @@ def pwm_on(self, t2_prescale, full_period, on_period):
                           full_period to control duty cycle. For
                           example:
 
-                              # 4MHz / 16 with 50% duty cycle
+                              # 12MHz / 16 with 50% duty cycle
                               codebug.pwm_on(T2_PS_1_16, 0xff, 0x200)
 
         """
@@ -203,14 +203,13 @@ def pwm_freq(self, frequency):
 
         """
         # calculate pwm settings
-        # 4 MHz / 16 = 250k ticks per second
-        full_period = int(250000 / frequency) - 1
+        # 12MHz / 16 = 750k ticks per second
+        full_period = int(750000 / frequency) - 1
         # for 50% duty cycle: shift up by 2 then /(2 i.e. 50% duty cycle)
         # on_period = (full_period << 2) / 2;
         # this is quicker
         on_period = full_period << 1
         self.pwm_on(T2_PS_1_16, full_period, on_period)
-        pass
 
     def pwm_off(self):
         go_busy_off_mask = 0xff ^ (1 << 4)

codebug_tether/version.py

@@ -1 +1 @@
-__version__ = '0.7.3'
+__version__ = '0.7.4'