RTT Logging in NCS: messages lost

[Bruno Randolf]

Hello,

I am trying to get reliable log output using the Nordic Connect SDK (NCS) over RTT.  When I use Minimal mode, the following config:

CONFIG_LOG_MODE_MINIMAL=y
CONFIG_SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL=y

I get the following output at startup. It includes everything I want to log.

*** Booting Zephyr OS build v2.7.99-ncs1-1  ***
W: Starting MyProject
I: Set up button at GPIO_0 pin 11
I: ACCEL init
E: No device found
I: SoftDevice Controller build revision:
I: 0e e7 c5 66 67 18 3c ac |...fg.<.
I: b3 d2 cc 81 a3 dc f1 c0 |........
I: c0 36 02 22             |.6."
I: HW Platform: Nordic Semiconductor (0x0002)
I: HW Variant: nRF52x (0x0002)
I: Firmware: Standard Bluetooth controller (0x00) Version 14.50663 Build 1008232294
I: Identity: D4:39:D6:4B:AC:BF (random)
I: HCI: version 5.2 (0x0b) revision 0x12fe, manufacturer 0x0059
I: LMP: version 5.2 (0x0b) subver 0x12fe
I: Bluetooth initialized

+ 20 lines of my own debug output

But MINIMAL logging mode has several disadvantages, so I try to use CONFIG_LOG2_MODE_DEFERRED, but the following happens:

*** Booting Zephyr OS build v2.7.99-ncs1-1  ***
[00:00:00.000,152] <wrn> main: Starting LocBeacon2
[00:00:00.500,518] <inf> gpio: Set up button at GPIO_0 pin 11
[00:00:00.500,549] <inf> accel: ACCEL init
[00:00:00.500,549] <err> accel: No device found
[00:00:00.500,671] <inf> sdc_hci_driver: SoftDevice Controller build revision:
                                         0e e7 c5 66 67 18 3c ac  b3 d2 cc 81 a3 dc f1 c0 |...fg.<. ........
                                         c0 36 02 22                                      |.6."             
[00:00:00.504,241] <inf> bt_hci_core: HW Platform: Nordic Semiconductor (0x0002)
[00:00:00.504,272] <inf> bt_hci_core: HW Variant: nRF52x (0x0002)
[00:00:00.504,302] <inf> bt_hci_core: Firmware: Standard Bluetooth controller (0x00) Version 14.50663 Build 1008232294
[00:00:00.505,584] <inf> bt_hci_core: Identity: D4:39:D6:4B:AC:BF (random)
[00:00:00.505,615] <inf> bt_[0m
0m

Logging is stopped at the HCI output and truncated from there on. My own log output is lost, after that logging works based on the events in the system, but that usually does not generate many lines of output.

I tried the following config with no improvement:

CONFIG_LOG_BUFFER_SIZE=8192
CONFIG_SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL=y
CONFIG_LOG_BLOCK_IN_THREAD=y

How can I have reliable RTT logging of more (all!) log messages, especially at system startup?

[Einar Thorsrud]

Hi,

Can you try to increase the RTT buffer size as well, using (say) CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=4096?

[Bruno Randolf]

Yes, okay, that works. Interestingly then the following config is not needed, maybe because the initial output all fits into the RTT buffer? I would conclude then that there must be a bug with blocking when the RTT buffer is full.

#CONFIG_LOG_BLOCK_IN_THREAD=y
#CONFIG_LOG_BUFFER_SIZE=4096
#CONFIG_SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL=y

[Einar Thorsrud]

Hi,

Even if you use CONFIG_LOG_BLOCK_IN_THREAD=y there is a timeout which is 1000 (ms) by default, specified by CONFIG_LOG_BLOCK_IN_THREAD_TIMEOUT_MS. If you set this to -1, the logger will block forever if needed.