Fix serial sync errors caused by multi thread collision #17
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SYMPTOM: Unpredictable errors when calling roboclaw API, manifesting in several different forms such as "OSError: 11" CAUSE: The roboclaw API is not thread-safe, but we have three different threads potentially calling into the API simultaneously. When this occurs, errors follow. 1. self.run for our '/odom' publisher thread 2. self.cmd_vel_callback as '/cmd_vel' subscriber 3. self.check_vitals running for diagnostics FIX: Use a threading.Lock() object to synchronize usage of roboclaw API object. Thereby ensuring only one thread will be communicating with roboclaw at any given time. REFERENCES: ROS Python API Threading Model https://answers.ros.org/question/9543/rospy-threading-model/ StackOverflow "Semaphores on Python" https://stackoverflow.com/questions/31508574/semaphores-on-python
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SYMPTOM: Unpredictable errors when calling roboclaw API, manifesting
in several different forms such as "OSError: 11"
CAUSE: The roboclaw API is not thread-safe, but we have three different
threads potentially calling into the API simultaneously. When this
occurs, errors follow.
FIX: Use a threading.Lock() object to synchronize usage of roboclaw
API object. Thereby ensuring only one thread will be communicating
with roboclaw at any given time.
REFERENCES:
ROS Python API Threading Model
https://answers.ros.org/question/9543/rospy-threading-model/
StackOverflow "Semaphores on Python"
https://stackoverflow.com/questions/31508574/semaphores-on-python