[ROS 2] RPLiDAR A1 auto standby not working properly

[jarkenau]

To my understanding, the code responsible for the auto standby assumes that the motor has been started (e.g a node subscribing to the /scan topic) before it can be stopped. This is because is_scanning must be true before the motor can be automatically stopped.

rplidar_ros/src/rplidar_node.cpp

Lines 441 to 443 in f0ace62

	else if (scan_pub->get_subscription_count() == 0) {
	if (is_scanning) {
	this->stop();

is_scanning is only set in the start() method

rplidar_ros/src/rplidar_node.cpp

Line 346 in f0ace62

is_scanning = true;

which is only called if auto_standby is disabled or /scan has more than one subscriber

rplidar_ros/src/rplidar_node.cpp

Lines 438 to 439 in f0ace62

	if (scan_pub->get_subscription_count() > 0 && !is_scanning) {
	this->start();

rplidar_ros/src/rplidar_node.cpp

Line 416 in f0ace62

if (!auto_standby && !this->start()) {

A possible solution is to simply skip the check when having no subscribers. Due to the LIDAR starting spinning as soon as it gets power.