add '_is_deinited()' to guard against reads/writes on an inactive pin.

[Adafruit_Blinka-hackapet.git] / src / adafruit_blinka / microcontroller / generic_linux / sysfs_pwmout.py

diff --git a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
index c966b410a60939f3e3535b349003aa177d2780cc..3ce2ee3a195f2f1f3b26fb35b2af5976c9905bf6 100644 (file)
--- a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
+++ b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
@@ -22,6 +22,7 @@ class PWMOut(object):
 
     # Channel paths
     _export_path = "export"
+    _unexport_path = "unexport"
     _pin_path = "pwm{}"
 
     # Pin attribute paths
@@ -54,13 +55,13 @@ class PWMOut(object):
         self._open(pin, duty_cycle, frequency, variable_frequency)
 
     def __del__(self):
-        self.close()
+        self.deinit()
 
     def __enter__(self):
         return self
 
     def __exit__(self, t, value, traceback):
-        self.close()
+        self.deinit()
 
     def _open(self, pin, duty=0, freq=500, variable_frequency=False):
         self._channel = None
@@ -78,29 +79,54 @@ class PWMOut(object):
             raise ValueError("PWM channel does not exist, check that the required modules are loaded.")
 
         pin_path = os.path.join(channel_path, self._pin_path.format(self._pwmpin))
-        if not os.path.isdir(pin_path):
-            try:
-                with open(os.path.join(channel_path, self._export_path), "w") as f_export:
-                    f_export.write("%d\n" % self._pwmpin)
-            except IOError as e:
-                raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror)
+        try:
+            with open(os.path.join(channel_path, self._unexport_path), "w") as f_unexport:
+                f_unexport.write("%d\n" % self._pwmpin)
+        except IOError as e:
+            pass # not unusual, it doesnt already exist
+        try:
+            with open(os.path.join(channel_path, self._export_path), "w") as f_export:
+                f_export.write("%d\n" % self._pwmpin)
+        except IOError as e:
+            raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror)
 
-        self._set_enabled(True)
+        #self._set_enabled(False) # This line causes a write error when trying to enable
 
         # Look up the period, for fast duty cycle updates
         self._period = self._get_period()
 
+        #self.duty_cycle = 0  # This line causes a write error when trying to enable
+
         # set frequency
         self.frequency = freq
         # set duty
         self.duty_cycle = duty
 
-    def close(self):
-        """Close the sysfs PWM."""
+        self._set_enabled(True)
+
+    def deinit(self):
+        """Deinit the sysfs PWM."""
+        if self._channel is not None:
+            self.duty_cycle = 0
+            try:
+                channel_path = os.path.join(self._sysfs_path, self._channel_path.format(self._channel))
+                with open(os.path.join(channel_path, self._unexport_path), "w") as f_unexport:
+                    f_unexport.write("%d\n" % self._pwmpin)
+            except IOError as e:
+                raise PWMError(e.errno, "Unexporting PWM pin: " + e.strerror)
+
         self._channel = None
         self._pwmpin = None
 
+    def _is_deinited(self):
+        if self._pwmpin is None:
+            raise ValueError("Object has been deinitialize and can no longer "
+                             "be used. Create a new object.")
+
     def _write_pin_attr(self, attr, value):
+        # Make sure the pin is active
+        self._is_deinited()
+
         path = os.path.join(
             self._sysfs_path,
             self._channel_path.format(self._channel),
@@ -112,6 +138,9 @@ class PWMOut(object):
             f_attr.write(value + "\n")
 
     def _read_pin_attr(self, attr):
+        # Make sure the pin is active
+        self._is_deinited()
+
         path = os.path.join(
             self._sysfs_path,
             self._channel_path.format(self._channel),
@@ -172,16 +201,15 @@ class PWMOut(object):
 
         # convert to 16-bit
         duty_cycle = int(duty_cycle * 65535)
-
         return duty_cycle
 
     def _set_duty_cycle(self, duty_cycle):
-        # convert from 16-bit
-        duty_cycle /= 65535
-
         if not isinstance(duty_cycle, (int, float)):
             raise TypeError("Invalid duty cycle type, should be int or float.")
-        elif not 0.0 <= duty_cycle <= 1.0:
+
+        # convert from 16-bit
+        duty_cycle /= 65535.0
+        if not 0.0 <= duty_cycle <= 1.0:
             raise ValueError("Invalid duty cycle value, should be between 0.0 and 1.0.")
 
         # Convert duty cycle from ratio to seconds