RTT logging interferes with USB

[Jefferson]

I am using RTT logging and it is interfering with USB HID data transfer.  The host sends consecutive OUT packets and I print some logs after each one.  I will miss a APP_USBD_HID_USER_EVT_OUT_REPORT_READY event sometimes.  I am doing this in the main loop:

while (1) {

while (app_usbd_event_queue_process())
{
;
}

//process data and print to log

if (NRF_LOG_PROCESS() == false)
{
nrf_pwr_mgmt_run();
}

}

Is this the correct way to handle USB?  I copied it from the USB HID examples.  If I turn off logging or set APP_USBD_CONFIG_EVENT_QUEUE_ENABLE to 0 then I don't see this problem.

[Jimmy Wong]

I used the nRF52840 dongle as the example and add the logger through USB.
it may be useful for your case.
jimmywongiot.com/.../
github.com/.../

[Edvin]

Do you use deferred logging? Please check the definition of NRF_LOG_DEFERRED in sdk_config.h. If it is not set to 1, can you try to set it to 1?

[Jefferson]

I tried setting to 1 and 0 and both don't work.

[Edvin]

Then I guess this requires more information on what your application does, and what the "//process data and print to log" does. 

Keep NRF_LOG_DEFERRED set to 1, since this will only process logging when nothing else requires attention. 

Just to clarify something: Are you trying to log RTT via the USB peripheral, or are you logging with RTT via the debugger, and at the same time using the USB for something else?

[Jefferson]

I am logging with debugger and using USB for HID.  I think the problem is how idle_state_handle() and nrf_pwr_mgmt_run() is handled by the SDK and all examples.  It does not work in many cases.  When running NRF_LOG_PROCESS() and it returns false, a USB event could occur but nrf_pwr_mgmt_run() would be run and could be stuck in sleep if no more USB events occur.  Setting USB events to interrupts fixes the problem in most cases but there is still some time for interrupt to occur before entering sleep mode and getting stuck in sleep.