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[hackapet/Adafruit_Blinka.git] / src / adafruit_blinka / microcontroller / bcm283x / pulseio / PulseIn.py

diff --git a/src/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py b/src/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py
index 6b86614b43418d263e668f58eee4878adb84e414..fd9febee7dabdbe70f5fec1bd3d9810fb2943b43 100644 (file)
--- a/src/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py
+++ b/src/adafruit_blinka/microcontroller/bcm283x/pulseio/PulseIn.py
@@ -25,7 +25,7 @@ def final():
 
 atexit.register(final)
 
-# pylint: disable=c-extension-no-member
+# pylint: disable=c-extension-no-member, consider-using-with
 class PulseIn:
     """PulseIn Class to read PWM signals"""
 
@@ -45,7 +45,9 @@ class PulseIn:
                 print("Message Queue Key: ", self._mq.key)
             queues.append(self._mq)
         except sysv_ipc.ExistentialError:
-            raise RuntimeError("Message queue creation failed")
+            raise RuntimeError(
+                "Message queue creation failed"
+            ) from sysv_ipc.ExistentialError
 
         dir_path = os.path.dirname(os.path.realpath(__file__))
         cmd = [
@@ -68,24 +70,29 @@ class PulseIn:
         # wait for it to start up
         if DEBUG:
             print("Waiting for startup success message from subprocess")
-        message = self._wait_receive_msg()
+        message = self._wait_receive_msg(timeout=0.25)
         if message[0] != b"!":
             raise RuntimeError("Could not establish message queue with subprocess")
         self._paused = False
 
     # pylint: disable=redefined-builtin
-    def _wait_receive_msg(self, timeout=0.25, type=2):
+    def _wait_receive_msg(self, timeout=0, type=2):
         """Internal helper that will wait for new messages of a given type,
         and throw an exception on timeout"""
-        stamp = time.monotonic()
-        while (time.monotonic() - stamp) < timeout:
-            try:
-                message = self._mq.receive(block=False, type=type)
-                return message
-            except sysv_ipc.BusyError:
-                time.sleep(0.001)  # wait a bit then retry!
-        # uh-oh timed out
-        raise RuntimeError("Timed out waiting for PulseIn message")
+        if timeout > 0:
+            stamp = time.monotonic()
+            while (time.monotonic() - stamp) < timeout:
+                try:
+                    message = self._mq.receive(block=False, type=type)
+                    return message
+                except sysv_ipc.BusyError:
+                    time.sleep(0.001)  # wait a bit then retry!
+            # uh-oh timed out
+            raise RuntimeError(
+                "Timed out waiting for PulseIn message. Make sure libgpiod is installed."
+            )
+        message = self._mq.receive(block=True, type=type)
+        return message
 
     # pylint: enable=redefined-builtin