Optimize the bootup time in nRF Connect SDK 2.4.2

[Stephen Long Jr]

Hello.

My name is Stephen and I am developing a beacon device using nRF52840 and Zephyr. I am using ncs 2.4.2. I need to optimize the boot-up time. I triggered the GPIO pin in the first line of the main function and measure time interval after VDD is triggered. At then, the boot up is 21.7ms. I need to reduce the boot-time less 10ms. To disable the log, I used the following proj.conf.

CONFIG_MULTITHREADING=y
CONFIG_LOG=n
CONFIG_SERIAL=n
CONFIG_CONSOLE=n
CONFIG_PRINTK=n
CONFIG_SHELL=n
CONFIG_UART_CONSOLE=n
CONFIG_USE_SEGGER_RTT=n
CONFIG_BOOTLOADER_MCUBOOT=n

CONFIG_BT=y
CONFIG_BT_EXT_ADV=y
CONFIG_BT_PER_ADV=y
CONFIG_BT_CTLR_PHY_CODED=y
CONFIG_BT_USER_PHY_UPDATE=y
CONFIG_BT_HCI=y
CONFIG_BT_CTLR=y
CONFIG_BT_CTLR_TX_PWR_PLUS_8=y
CONFIG_BT_DEBUG_LOG=n
CONFIG_BT_DEVICE_NAME="WePower"
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_250PPM=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n
#CONFIG_BOARD_ENABLE_DCDC=y
# From Nordic to disable Crypto RNG
CONFIG_HW_CC3XX=n
CONFIG_ENTROPY_CC3XX=n
CONFIG_ENTROPY_NRF5_RNG=y
CONFIG_CC3XX_BACKEND=n
# Software Crypto with Mbed
CONFIG_MBEDTLS=y
CONFIG_MBEDTLS_BUILTIN=y
CONFIG_MBEDTLS_HEAP_SIZE=512
CONFIG_MBEDTLS_CIPHER_CCM_ENABLED=y
CONFIG_MBEDTLS_CIPHER_GCM_ENABLED=y
CONFIG_CRYPTO=y
CONFIG_CRYPTO_MBEDTLS_SHIM=y
# GPIO
CONFIG_GPIO=y
CONFIG_NRFX_GPIOTE=y
# I2C
CONFIG_I2C=y
CONFIG_I2C_NRFX=y
CONFIG_NRFX_TWIM0=y
CONFIG_SENSOR=y
CONFIG_LIS2DW12=y
CONFIG_LPS22HH=y
CONFIG_LPS22HH_TRIGGER_NONE=n
CONFIG_CBPRINTF_FP_SUPPORT=n

But the boot-time was not updated.  I'd appreciate it if anyone can help me to solve this issue. I attached the screenshot of boot-up time.

Thank you,

Stephen

[Kenneth]

Hello,

Are you able to provide some more information about the use case? You write you need the boot time to take less than 10ms, but I want to understand why that is so I can understand what problem you are trying to solve.

For instance if you need fast startup time you may consider using system on idle instead of power off, the difference in current consumption is ~2uA, but then the device will wakeup close to immediately, since the application don't need to boot up on wakeup.

If you need to use system off, but also less than 10ms I don't see much alternatives, since the boot will setup the entire board (e.g. init external sensors during boot) and this will take some time. However it could still be possible to add a sys init during boot if you just need to read a pin before reaching main when using system off.

Kenneth

[Stephen Long Jr]

Thank you for your reply. The device will be in the sleep mode. When reading the sensor, it will be activated. The problem is to reduce the boot-up time. The device needs to advertise the data every 20ms. So I want to reduce the bootup time to less than 20ms, if possible, 10ms. 

If I add the sys init function, can I read the GPIO pin while booting?

Regards,

Stephen

[Kenneth]

Hello,

I am sorry, but I don't understand the problem. May I ask if you have gone through the tutorials?
https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/ 
https://academy.nordicsemi.com/courses/bluetooth-low-energy-fundamentals/ 

Reason for asking is that there is no need to do a boot every 20ms, maybe the code is asserting and you thereby trigger a soft reset every 20ms.

Kenenth

[Stephen Long Jr]

our device is an energy-harvesting device. So the energy is not much. The long boot time is not so good.

The client wants to reduce the boot time to less than 10ms.

Stephen

[Kenneth]

Hello,

I would likely have commented out that i2c sensor and see if that have any impact. In any case, I think you should not only look at the time it takes, but also the current consumption during the period. Do you have access to a nordic power profiler kit II so you can measure the entire boot with current consumption? It's also possible to measure digital pins at the same time, so you can see for instance the button press, pin toggling when application start and even i2c if you like.

Kenneth