Can't set 100Hz for MAVLINK_MSG_ID_HIGHRES_IMU on Rover

[lida2003]

Setup:

• latest 4.6-dev
• 921600 (UAVT, MAVLinkv2)

same code from setting MAV_CMD_SET_MESSAGE_INTERVAL,MAVLINK_MSG_ID_HIGHRES_IMU to 100Hz, which is 10000 us.

Result:

• F435 Copter 100Hz OK
• H743 Copter 100Hz/200Hz OK
• H743 Rover NG about 50Hz

PS: Previous discussion hereCan't set 100Hz for MAVLINK_MSG_ID_HIGHRES_IMU?
#4.

[stephendade]

Just a guess, but the loop rate in Rover SCHED_LOOP_RATE is 50 by default. Trying increasing this to 100 or 200.

[lida2003]

I successfully set 10Hz(actually 9Hz), 25Hz(actually 24Hz), 50Hz(actually 49~50Hz), but I can't set 40Hz, 100Hz, 200Hz.

But it works for copter code 4.6-dev(same git commit code). It might be copter handles this command different from rover. I'm NOT digging into the code right now.

Just post this question here, maybe someone can take care of it when have time.

--- EDIT:

BTW, I can test if there is any debug version.

[stephendade]

Ok, I've done some digging and created a patch in #28144.

I've confirmed by initial guess that Ardupilot is indeed capping the message rate at SCHED_LOOP_RATE. Try setting this parameter to 250Hz and try your message rates again.

[lida2003]

I'll do the test tomorrow and get back to you soon.

--- EDIT

Yes, change loop rate helps. Is there any api for changing "SCHEDULER_LOOP_RATE"?

diff --git a/libraries/AP_Scheduler/AP_Scheduler.cpp b/libraries/AP_Scheduler/AP_Scheduler.cpp
index 7d21cf015a..cee4abc6fe 100644
--- a/libraries/AP_Scheduler/AP_Scheduler.cpp
+++ b/libraries/AP_Scheduler/AP_Scheduler.cpp
@@ -43,7 +43,7 @@
 #if APM_BUILD_COPTER_OR_HELI || APM_BUILD_TYPE(APM_BUILD_ArduSub)
 #define SCHEDULER_DEFAULT_LOOP_RATE 400
 #else
-#define SCHEDULER_DEFAULT_LOOP_RATE  50
+#define SCHEDULER_DEFAULT_LOOP_RATE 200
 #endif

GCS_MAVLINK::set_ap_message_interval is invoked in GCS_MAVLINK::set_message_interval

Does this mean we can remove this part in GCS_MAVLINK::set_ap_message_interval or maybe return false from set_ap_message_interval?

ardupilot/libraries/GCS_MAVLink/GCS_Common.cpp

Lines 1654 to 1660 in 075a5c3

	#if AP_SCHEDULER_ENABLED
	// send messages out at most 80% of main loop rate
	if (interval_ms != 0 &&
	interval_ms*800 < AP::scheduler().get_loop_period_us()) {
	interval_ms = AP::scheduler().get_loop_period_us()/800.0f;
	}
	#endif

[stephendade]

Is there any api for changing "SCHEDULER_LOOP_RATE"?

That's just an Ardupilot parameter that you can set via your GCS.

[lida2003]

Thanks.