Hal interfaces is a python package that provides the hardware abstraction layer for the various sensors and actuators used in the exercises of Robotics Academy.
In order to import the specific HAL interface follow the next pattern.
Being for general interfaces:
from hal_interfaces.general.{INTERFACE} import ...where {INTERFACE} needs to be substitued by the interface name.
And for specific interfaces:
from hal_interfaces.specific.{EXERCISE}.{INTERFACE} import ...where {EXERCISE} is the name of exercise being worked on and {INTERFACE} needs to be substitued by the interface name.
If the interface is only specific to one exercise add it as a specific interface, if not the add it to general. Also the naming scheme that needs to be followed when naming a new interface file is snake case or lower case with underlines.
For reference, please refer to the existing interfaces.
- Inside the general directory
- Create a directory named after the exercise name inside of the specific directory.
- Import each interface as stated in the How to use section.
- Initialize each interface
- For subscribers (interfaces that receive data) it is recommended to add them inside an executor thread as follows:
import rclpy
import sys
import threading
import time
freq = 60.0 # Desired iteration frequency for subscriber callback
def __auto_spin() -> None:
while rclpy.ok():
executor.spin_once(timeout_sec=0)
time.sleep(1/freq)
# Init the interfaces and start rclpy
#
#####################################
# Spin nodes so that subscription callbacks load topic data
executor = rclpy.executors.MultiThreadedExecutor()
# Add all of the interfaces that need to receive data
executor.add_node(my_interface_1)
executor.add_node(my_interface_2)
executor_thread = threading.Thread(target=__auto_spin, daemon=True)
executor_thread.start()