nRF9160 Using UART with printf without all the debugging outputs from Zephyr

[JonnyMN]

How do I use printf to output my own messages, and read incoming data, from a UART port that is separate from Zephyr's debugging outputs? This UART line will be connected to another microcontroller for custom commands.

Here is what I have so far:

I want printf messages to be directed to the UART0 port for my program to talk to another device. I also want to be able to read the incoming messages.

Here is my code that works:

while (1) {
		char *s = console_getline();
		printf("Here's your string: %s\n", s);
	}

However, with the above code, I also get what appears to be debug outputs from Zephyr being put on my UART0 line. For example, when the device starts up, I get a bunch of debug messages, etc. Also, any printk() messages are also on UART0.

I thought I could get around this by modifying the kconfig settings (via kconfig or guiconfig). I tried disabling things like the kernal boot banner, logging, etc, but the settings are reset to the defaults after rebuilding the project.

[Øyvind]

Hello, 

You can enable the Logging module of Zephyr by adding #include <logging/log.h> to e.g. main.c and the following lines to prj.conf

# Configure logger
CONFIG_LOG=y
CONFIG_USE_SEGGER_RTT=n
CONFIG_LOG_BACKEND_UART=y
CONFIG_LOG_DEFAULT_LEVEL=4

There are four severity levels available in the system: error, warning, info and debug.

In your main.c add the following lines just before your main loop.

#define LOG_MODULE_NAME app
LOG_MODULE_REGISTER(LOG_MODULE_NAME);

In you application you should be able to replace e.g the printk() with LOG_INF() for debug/logging information.  

This should provide you with the following output

Let me know how that works for you

[JonnyMN]

This did not fix my problem, unfortunately.

Just to clear up any confusion, this is what I'm seeing as the device starts up:

*** Booting Zephyr OS build v2.7.99-ncs1-1  ***
I: Starting bootloader
I: Primary image: magic=bad, swap_type=0x0, copy_done=0x2, image_ok=0x2
I: Secondary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
I: Boot source: none
I: Swap type: none
I: Bootloader chainload address offset: 0x10000
I: Jumping to the first image slot
*** Booting Zephyr OS build v2.7.99-ncs1-1  ***
Flash regions..Domain..Permissions
00 03 0x00000 0x20000 .Secure..rwxl
04 31 0x20000 0x100000 .Non-Secure.rwxl

Non-secure callable region 0 placed in flash region 3 with size 32.

SRAM region..Domain..Permissions
00 03 0x00000 0x08000 .Secure..rwxl
04 31 0x08000 0x40000 .Non-Secure.rwxl

Peripheral..Domain..Status
00 NRF_P0               Non-Secure.OK
01 NRF_CLOCK            Non-Secure.OK
02 NRF_RTC0             Non-Secure.OK
03 NRF_RTC1             Non-Secure.OK
04 NRF_NVMC             Non-Secure.OK
05 NRF_UARTE1           Non-Secure.OK
06 NRF_UARTE2           Secure..SKIP
07 NRF_TWIM2            Non-Secure.OK
08 NRF_SPIM3            Non-Secure.OK
09 NRF_TIMER0           Non-Secure.OK
10 NRF_TIMER1           Non-Secure.OK
11 NRF_TIMER2           Non-Secure.OK
12 NRF_SAADC            Non-Secure.OK
13 NRF_PWM0             Non-Secure.OK
14 NRF_PWM1             Non-Secure.OK
15 NRF_PWM2             Non-Secure.OK
16 NRF_PWM3             Non-Secure.OK
17 NRF_WDT              Non-Secure.OK
18 NRF_IPC              Non-Secure.OK
19 NRF_VMC              Non-Secure.OK
20 NRF_FPU              Non-Secure.OK
21 NRF_EGU0             Non-Secure.OK
22 NRF_EGU1             Non-Secure.OK
23 NRF_EGU2             Non-Secure.OK
24 NRF_EGU3             Non-Secure.OK
25 NRF_EGU4             Non-Secure.OK
26 NRF_EGU5             Non-Secure.OK
27 NRF_DPPIC            Non-Secure.OK
28 NRF_REGULATORS       Non-Secure.OK
29 NRF_PDM              Non-Secure.OK
30 NRF_I2S              Non-Secure.OK
31 NRF_GPIOTE1          Non-Secure.OK

SPM: NS image at 0x20200
SPM: NS MSP at 0x20015338
SPM: NS reset vector at 0x25ec1
SPM: prepare to jump to Non-Secure image.
*** Booting Zephyr OS build v2.7.99-ncs1-1  ***

I don't want any of these messages on my UART 0 port. I only want messages that I send using printf() function in my code only. 

Here is what I want to see during device startup:

// nothing, but I had to put something here since the code block wont let me post without any text.

[Øyvind]

Ok, I see. You could use e.g. RTT for logs. See RTT chapter in Logging in nRF Connect SDK. To turn off the "boot banner" you can add CONFIG_BOOT_BANNER=n. 

Also, please see the Zephyr Logging API. 

[JonnyMN]

I added the following to my prj.conf file:

CONFIG_BOOT_BANNER=n

CONFIG_LOG=y
CONFIG_LOG_MODE_MINIMAL=y
CONFIG_LOG_BACKEND_UART=n
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y

But it had no effect. Boot banner and all the Zephyr start-up messages are still present on UART0.

[JonnyMN]

Are there any updates on this? Again, I want to silence all outputs to the UART0, and only transmit data I send out via a printf() function.

[Øyvind]

My apologies for the late answer. Can you please add the following folder and file to your project folder: child_image/spm.conf

In this file, add the following line: CONFIG_SERIAL=n

Then, in your prj.conf add the following:

CONFIG_UART_CONSOLE=n

CONFIG_RTT_CONSOLE=y 

Let me know how that works for you. 

Kind regards,
Øyvind