How to use rmw_uros_ping_agent() and rmw_uros_sync_session() correctly ?

Dear all,

I am currently implementing micro-ros client on a RP2040 Pico board to publish the IMU data every 5ms (i.e. 200Hz).
Each time I need to publish the data, I check the connection of which transport layer is serial over USB knowing that its typical latency is reported here : https://docs.vulcanexus.org/en/iron/rst/microros_documentation/benchmarking/benchmarking.html#latency

However, measuring the time (in microsecs) taken by critical code in my implementation gives:

proc_imu() already took : 415
proc_baro() already took : 9
**check_connection() already took : 2635**
publish() already took : 1645
Whole loop() already took : 6709

As one could see, the whole loop() exceeded the expected 5ms and the most critical function is **check_connection()** which is implementated as below :
void check_connection(){
switch (uros_conn_curr_state) {
case WAITING_AGENT:
EXECUTE_EVERY_N_MS(5, uros_conn_curr_state = (RMW_RET_OK == rmw_uros_ping_agent(100, 1)) ? AGENT_AVAILABLE : WAITING_AGENT;);
break;
case AGENT_AVAILABLE:
uros_conn_curr_state = (true == **create_entities()**) ? AGENT_CONNECTED : WAITING_AGENT;
if (uros_conn_curr_state == WAITING_AGENT) {
destroy_entities();
};
break;
case AGENT_CONNECTED:
EXECUTE_EVERY_N_MS(500, uros_conn_curr_state = (RMW_RET_OK == rmw_uros_ping_agent(100, 1)) ? AGENT_CONNECTED : AGENT_DISCONNECTED;);
if (uros_conn_curr_state == AGENT_CONNECTED) {
rclc_executor_spin_some(&executor, 1000);
};
break;
case AGENT_DISCONNECTED:
destroy_entities();
uros_conn_curr_state = WAITING_AGENT;
break;
default:
break;
}
}

And the rmw_uros_sync_session() is call within create_entities() :
bool create_entities()
{

..

// create executor
executor = rclc_executor_get_zero_initialized_executor();
RCCHECK(rclc_executor_init(&executor, &support.context, 2, &allocator));
RCCHECK(rclc_executor_add_service(&executor, &service_fps, &req_fps, &res_fps, service_fps_callback));
RCCHECK(rclc_executor_add_service(&executor, &service_exp, &req_exp, &res_exp, service_exp_callback));

RCSOFTCHECK(rmw_uros_sync_session(timeout_ms));

return true;
}

I put my doubt on the **rmw_uros_ping_agent()** function according to some issue reports, one of them is : https://github.com/micro-ROS/micro_ros_arduino/issues/506

To update, I also found cases that the **check_connection()** took less than 1ms but the publish() took > 6ms :
proc_imu() already took : 384
proc_baro() already took : 8
check_connection() already took : 953
**publish() already took : 6375**
Whole loop() already took : 9727

proc_imu() already took : 411
proc_baro() already took : 7
check_connection() already took : 986
**publish() already took : 6668**
Whole loop() already took : 10062

Thanks in advance for you advice / suggestion.
Khang

Commencez par check_connection() et create_entities(), puis suivez rmw_uros_ping_agent(), rmw_uros_sync_session(), publish() et rclc_executor_spin_some(). Reproduisez les timings signalés sur le RP2040 Pico avec serial-over-USB et déterminez si le délai est causé par le ping, la synchronisation de session, le travail de l’exécuteur ou la publication. Le travail est considéré comme terminé lorsque le comportement temporel et l’utilisation correcte de l’API sont documentés ou que le problème sous-jacent est identifié.

Rédigé par le modèle d'indexation à partir du texte de l'issue.