UART and Logger

RE: UART and Logger

Jim Logsdon — Mon, 25 Aug 2025 19:44:40 GMT

Please close this ticket.

RE: UART and Logger

SwRa — Thu, 30 Jan 2025 13:42:20 GMT

Hi James,

Could you try adding the following as well:

CONFIG_RTT_CONSOLE=y

CONFIG_UART_CONSOLE=n

CONFIG_LOG_MODE_IMMEDIATE=y

CONFIG_LOG_PRINTK=y

Ensure you're using the correct tool to view RTT output. The standard UART terminal won't show RTT logs. You need to use a tool like SEGGER's RTT Viewer or J-Link RTT Viewer or the RTT Console in nRF Connect for VS Code to see the RTT output.

Regards,

Swathy

RE: UART and Logger

Jim Logsdon — Thu, 23 Jan 2025 20:49:17 GMT

I'm not having success make the esb_ptx sample use the RTT instead of the UART. I've pasted the configuration you recommended into prj.conf as you recommended:

# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause

CONFIG_NCS_SAMPLES_DEFAULTS=y

CONFIG_ESB=y

CONFIG_DK_LIBRARY=y

CONFIG_CLOCK_CONTROL=y

CONFIG_USE_SEGGER_RTT=y

CONFIG_LOG=y

CONFIG_LOG_BACKEND_RTT=y

CONFIG_LOG_BACKEND_UART=n

The esb_ptx application still writes out the uart and not the RTT.

I get the following problems reported:

Any idea why it's not working?

RE: UART and Logger

SwRa — Thu, 23 Jan 2025 13:59:52 GMT

[quote user="Jim Logsdon"] Can you still use the debug interface for debugging while also using it as the Logger back end?[/quote]

Yes, it should be possible. 🙂

Regards,

Swathy

RE: UART and Logger

Jim Logsdon — Thu, 23 Jan 2025 13:53:25 GMT

Oh. That makes so much sense. Can you still use the debug interface for debugging while also using it as the Logger back end?

RE: UART and Logger

SwRa — Thu, 23 Jan 2025 13:43:31 GMT

Hi James,

RTT (Real-Time Transfer) on the nRF52 DK does not use a dedicated physical connection like UART does. Instead, RTT operates through the existing debug interface.

[quote user="Jim Logsdon"]I see that the UART is connected from the nRF52832 to the nRF5340, but I don't see anything connections labelled RTT.[/quote]

The RTT is not a peripheral on the nRF in the same way. RTT works by having the debugger read and write to specific memory locations on the nRF52832 chip. This means it doesn't require any additional pins or physical connections beyond what's already used for debugging. It is just the debugger reading some memory areas on the nRF, which doesn't affect the performance of the chip.

Best Regards,

Swathy

RE: UART and Logger

Jim Logsdon — Thu, 23 Jan 2025 13:19:43 GMT

Thank you for such a quick response! I will work to use the RTT for logging.

What is the physical layer for RTT on the nRF52DK board?

I see that the UART is connected from the nRF52832 to the nRF5340, but I don't see anything connections labelled RTT.

Thanks, and hopefully this is my last question.

Jim

RE: UART and Logger

SwRa — Thu, 23 Jan 2025 12:45:35 GMT

Hi James,

UART0 is usually used for logging.. The logging module can be configured to use a different backend, such as the RTT.. This ensures that the UART instance is free to be used for your application.. To do this, you need to add the following to prj.conf:

CONFIG_USE_SEGGER_RTT=y

CONFIG_LOG=y

CONFIG_LOG_BACKEND_RTT=y

CONFIG_LOG_BACKEND_UART=n

You could also use another UART instance (eg.: you can use UART1 to receive data if UART0 is used for logging)

Regards,

Swathy