ros::NodeHandle::getParam causing error when CORE2 is flashed

Software
1

Hello,

I am trying to pass some parameters to my serial node through the following node definition:

    <node pkg="rosbot-maze-navigator" type="serial_bridge.sh" name="bridge" output="screen">
        <param name="base_frame" value="$(arg BASE_FRAME)"/>
        <param name="odom_frame" value="$(arg ODOM_FRAME)"/>
        <param name="odometry_reset_topic" value="$(arg ODOMETRY_RESET_TOPIC)"/>
        <param name="pose_topic" value="$(arg POSE_TOPIC)"/>
        <param name="baudrate" value="$(arg SERIAL_BAUDRATE)"/>
        <param name="spin_rate" value="$(arg SERIAL_SPINRATE)"/>
    </node>

To be able to access these parameters from the node, I am using the following method:

char *base_frame;
[...]
node_handle.getParam("base_frame", &base_frame);

The code successfully gets built & CORE2 gets flashed. However, with the following warning:

C:/Users/erinc/.vscode/extensions/husarion.husarion-1.5.28/sdk/include/hROS/ros/node_handle.h: In instantiation of 'bool ros::NodeHandle_<Hardware, MAX_SUBSCRIBERS, MAX_PUBLISHERS, INPUT_SIZE, OUTPUT_SIZE>::getParam(const char*, char**, int) [with Hardware = hROSHardware; int MAX_SUBSCRIBERS = 25; int MAX_PUBLISHERS = 25; int INPUT_SIZE = 512; int OUTPUT_SIZE = 512]':
D:\Projects\rosbot-labyrinth\main.cpp:77:51:   required from here
C:/Users/erinc/.vscode/extensions/husarion.husarion-1.5.28/sdk/include/hROS/ros/node_handle.h:530:22: warning: comparison between
signed and unsigned integer expressions [-Wsign-compare]
           if (length == req_param_resp.strings_length){
                      ^

I don’t think this warning causes the problem, but the LEDs start to flash when I flash CORE2 with the mentioned code.

What can be wrong with this call? Is there a correct way to access serial node parameters?

Thanks,
Erinc

2

Hello Erinc,

There are some steps to set parameter on CORE2, first parameter for CORE2 sholud be set globally, outside of node scope:

  <param name="base_frame" value="$(arg BASE_FRAME)"/>
  <param name="odom_frame" value="$(arg ODOM_FRAME)"/>
  <param name="odometry_reset_topic" value="$(arg ODOMETRY_RESET_TOPIC)"/>
  <param name="pose_topic" value="$(arg POSE_TOPIC)"/>
  <param name="spin_rate" value="$(arg SERIAL_SPINRATE)"/>

  <node pkg="rosbot-maze-navigator" type="serial_bridge.sh" name="bridge" output="screen">    
      <param name="baudrate" value="$(arg SERIAL_BAUDRATE)"/>
  </node>

Then to retrieve parameters:

float paramter[1];
// wait until node is connected
while (!nh.connected())
{
	nh.spinOnce();
}

// retrieve params
if (!nh.getParam("param_name", parameter, 1))
{
	//default values
	parameter[0] = 1;
}

You can find more details regarding parameters in rosserial documentation

Regards,
Łukasz

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