nRF52832 application won't start without RTT console

[Alex-Uzinakod]

Hi, we're trying to run our nRF52832 without having to connect the RTT console debugger to launch the main application loop. So that an other team could just power the board and interact with the bluetooth firmware using the nRF Connect for Mobile app.

We managed to get the internal clock working and the nRST pin is switched from LOW to HIGH at the board boot (validated using a multimeter).

There's one last thing in our way, we absolutely need to connect to the RTT terminal to launch the main loop. That happens even when the debug option is turned off in the build configuration.

Is there a flag missing from our configuration?

 

Hardware:

• J-Link programmer
• USI AzureSphere combo module evaluation board (combines an Azure Sphere and an nRF52832 BLE chip)

Software:

• nRF Connect SDK v2.3.0
• nRF Toolchain v2.3.0
• nRF Connect for VS Code

 

We started from the following example https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/bluetooth/peripheral

proj.conf:

# Enable Bluetooth peripheral
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
CONFIG_DEBUG=n

# Config logger
CONFIG_LOG=n
CONFIG_BT_DEBUG_LOG=n
CONFIG_CONSOLE=n
CONFIG_USE_SEGGER_RTT=n
CONFIG_BT_DEBUG_MONITOR_RTT=n
CONFIG_LOG_BACKEND_RTT=n
CONFIG_LOG_BACKEND_UART=n
CONFIG_LOG_PRINTK=n

# Power management
CONFIG_PM=n

# Drivers and peripherals
CONFIG_I2C=n
CONFIG_WATCHDOG=n
CONFIG_PINMUX=n
CONFIG_SPI=n

# Boot
CONFIG_BOOT_BANNER=n
CONFIG_BOOT_DELAY=0

# Increased stack due to settings API usage
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

# Enable Secure Connections Only mode
# CONFIG_BT_SMP=y
# CONFIG_BT_TINYCRYPT_ECC=y
# CONFIG_BT_SMP_SC_ONLY=y
# CONFIG_BT_SMP_ENFORCE_MITM=y

# Use settings for BLE bonding
CONFIG_BT_SETTINGS=y
CONFIG_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_FCB=y
# CONFIG_BT_SIGNING=y
# CONFIG_BT_PRIVACY=y
CONFIG_BT_ATT_PREPARE_COUNT=5

## Battery Service
CONFIG_BT_BAS=y

## Device Information Service
CONFIG_BT_DIS=y
CONFIG_BT_DIS_PNP=n
### Manufacturer
CONFIG_BT_DIS_MANUF="Motion Composites inc."
### Model
CONFIG_BT_DIS_MODEL="Newton Power Assist"
### Revision
CONFIG_BT_DIS_HW_REV=y
CONFIG_BT_DIS_HW_REV_STR="Rev. C"
### Serial number
CONFIG_BT_DIS_SERIAL_NUMBER=n
CONFIG_BT_DIS_SERIAL_NUMBER_STR=""
### Powered Wheelchair
CONFIG_BT_DEVICE_APPEARANCE=3265

## Naming options
CONFIG_BT_DEVICE_NAME="NPA"
### Allows to set a name at runtime (ex: with a random id)
CONFIG_BT_DEVICE_NAME_DYNAMIC=y
CONFIG_BT_DEVICE_NAME_MAX=10
# CONFIG_BT_BONDING_REQUIRED=n
## Used to hide the BT device after connection to a central device.
# CONFIG_BT_FILTER_ACCEPT_LIST=y 

# CONFIG_BT_KEYS_OVERWRITE_OLDEST=y
## Required to set a non random key
# CONFIG_BT_FIXED_PASSKEY=y
CONFIG_NVS=y

CONFIG_BT_GATT_DYNAMIC_DB=y


# TODO: Disable for Release build
CONFIG_ASSERT=n

# This configures the SDK for the BLE NRF chip
# You can find the documentation for each setting here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/kconfig/index.html
# Search for the setting in the KConfig search engine
CONFIG_CLOCK_CONTROL=y
CONFIG_CLOCK_CONTROL_NRF=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC_CALIBRATION=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_500PPM=y

[JONATHAN LL]

There's one last thing in our way, we absolutely need to connect to the RTT terminal to launch the main loop.

Do you need to connect any RTT viewer terminal before the device works as intended or is it just a physical connection from the J-LINK?

Wondering if this could be a power issue as there should not be anything prohibiting the software from launching wit out RTT connected. Do you have a datasheet of the board? or a user guide?

Regards,
Jonathan

[Alex-Uzinakod]

I tested with the J-Link being connected but no RTT viewer connected and the firmware doesn't launch. I absolutly need to connect the RTT viewer to get the main loop to start running even when compiling as Release.

I'm using a board that has no documentation available online. Here's the documentation for a board similar to the one I'm using that's from the same company. fcc.report/.../4772970.pdf

[JONATHAN LL]

Thanks, can't see any issues here. Is it possible for you to test the code on different hardware ? Possibly a 52DK?

There doesn't seem to be anything that would indicate that RTT must be running for the application to work.

Regards

Jonathan 

[Alex-Uzinakod]

We don't have a devkit at the moment. We might order one to figure out if the behaviour is the same on different hardware.

In the mean time, we'll plug an oscilloscope on the J-Link pins to figure out what's happening when the RTT console connects to the nRF52 chip. Do you think this could help you help us figure out what's happening?

[JONATHAN LL]

You can try with a different code firs maybe, a simpler app like pin toggle or some other task. simple loop that prints or blinks led/toggles pin. 

So just try to rule out software first. 


Using a scope could help shed some light on what is going on. If there is a voltage enabled on one of the pins first after the RTT connection is enabled then that would indicate that you might have a power issue. 

With a alterative HW you can at least test you software.

Is the external low frequency freq/clock enabled in software? If that is the case and there is no physical low freq crystal then this often causes issues. 

Regards,
Jonathan

[Alex-Uzinakod]

I figured out my error, I wasn't enabling the bootloader build. See https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/application_development/sysbuild/with_mcuboot/README.html for details.

[JONATHAN LL]

Great! and thanks for updating us with the solution.