Custom board for nRF52811 in nRFConnect - code halts on z_log_minimal_printk() in CONFIG_UART_CONSOLE=y, but if RTT console is used, code debugs fine.

Question

Hi there

#
# Copyright (c) 2020 Nordic Semiconductor
#
# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
#
CONFIG_NCS_SAMPLES_DEFAULTS=y
CONFIG_DK_LIBRARY=y
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

# CONFIG_BT=y
# CONFIG_BT_PERIPHERAL=y
# CONFIG_BT_DEVICE_NAME="ElixirS2-PPI"
# CONFIG_BT_MAX_CONN=2
# CONFIG_BT_SMP=y
# CONFIG_BT_MAX_PAIRED=2

# Enable the BMS service
# CONFIG_BT_BMS=y

# Enable bonding
# CONFIG_BT_SETTINGS=y
# CONFIG_FLASH=y
# CONFIG_FLASH_PAGE_LAYOUT=y
# CONFIG_FLASH_MAP=y
# CONFIG_NVS=y
# CONFIG_SETTINGS=y

# ADC Stuff
CONFIG_DYNAMIC_INTERRUPTS=y
CONFIG_NRFX_SAADC=y
CONFIG_NRFX_SPIM1=y
CONFIG_NRFX_TIMER0=y
CONFIG_NRFX_TIMER1=y
CONFIG_NRFX_TIMER2=y
CONFIG_NRFX_RTC0=y

# Logging to RTT
#CONFIG_USE_SEGGER_RTT=y
#CONFIG_RTT_CONSOLE=y
CONFIG_UART_CONSOLE=y
CONFIG_LOG_DEFAULT_LEVEL=3
CONFIG_LOG_MAX_LEVEL=4
CONFIG_LOG_PRINTK=y


CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

prj.conf

// Copyright (c) 2021 Nordic Semiconductor ASA
// SPDX-License-Identifier: Apache-2.0

/dts-v1/;
#include <nordic/nrf52811_qfaa.dtsi>

/ {
	model = "LX_ElixirS2";
	compatible = "LX-nrf52811";

	chosen {
		zephyr,console = &uart0;
		zephyr,shell-uart = &uart0;
		zephyr,uart-mcumgr = &uart0;
		zephyr,bt-mon-uart = &uart0;
		zephyr,bt-c2h-uart = &uart0;
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
		zephyr,code-partition = &slot0_partition;
	};
};

&adc {
	status = "okay";
};

&gpiote {
	status = "okay";
};

&gpio0 {
	status = "okay";
};

&uart0 {
	status = "okay";
	compatible = "nordic,nrf-uarte";
	current-speed = <115200>;
	tx-pin = <9>;
	rx-pin = <8>;
//	rts-pin = <5>;
//	cts-pin = <7>;
};

&spi1 {
	compatible = "nordic,nrf-spi";
	status = "okay";
	sck-pin = <18>;
	mosi-pin = <17>;
	miso-pin = <16>;
};

&flash0 {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x0 0xc000>;
		};
		slot0_partition: partition@c000 {
			label = "image-0";
			reg = <0xc000 0xa000>;
		};
		slot1_partition: partition@16000 {
			label = "image-1";
			reg = <0x16000 0xa000>;
		};
		scratch_partition: partition@20000 {
			label = "image-scratch";
			reg = <0x20000 0xa000>;
		};
		storage_partition: partition@2a000 {
			label = "storage";
			reg = <0x2a000 0x6000>;
		};
	};
};

EXR-200-004.dts

/*
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

#include <kernel.h>
#include <nrfx_timer.h>

#include "hal/nrf_clock.h"

#include "Application/App_Sampling.h"

void main(void)
{
    // This stage of the product won't necessarily have and external xtal. Default to using the inernal RC.
    //nrf_clock_lf_src_set(NRF_CLOCK, NRF_CLOCK_LFCLK_RC);

    AppSampling_InitModule();

    AppSampling_InitRegister();

    k_sleep(K_FOREVER);
}

main.c

Please refer the .dts custom board file. We took a basic file generated from nRFConnect for nRF52811, and added in some missing bits which match our application, as found in the board definition for the nRF52832 Dev Kit. You will note on lines 41/42 we cannot decide what to do with the UART RTS/CTS pin definitions - we don't want to use any. But we feel that the processor may be blocking, waiting for a hardware CTS signal prior to sending debug content out the serial port. Is that what's going on?

In prj.conf, lines 38..40, if we enable the RTT instead, the application code works just fine (although we're not currently seeing any RTT output in the SeggerRTTViewer tool, perhaps beside the point, but worth mentioning.).

How would we best setup the configuration for TX/RX-only UART0 debug?

Thanks

Luke