Flashing target device from dev kit

[bdoan]

Is it necessary to use the 32768 crystal on the target device in order to flash that device using a connection to the nRF52 development board, or can the device use the internal RC oscillator?

if it can use the RC oscillator, how must the setup be changed?

[Menon]

Hello,

I have a doubt about your setup. Could you clarify this before answering the question? Are you using a nRF52dk to flash your target device? I strongly believe it is not necessary to use the 32.768 kHz crystal. I will confirm this after you clarify the setup.

if it can use the RC oscillator, how must the setup be changed?

For answering this, please share the SDK version you are trying with.

 

Kind Regards,

Abhijith

[bdoan]

The board is a PCA10040    3.0.0    2023.4

Please see :

https://infocenter.nordicsemi.com/pdf/nRF52_DK_User_Guide_v2.x.x.pdf 
page 21
4.8.2     Programming external boards using connector P20

also see page 17
4.6     32.768 kHz crystal

My overriding question is: "do I need to use the 32.768 kHz crystal at all in my custom board design and if not, what changes need to be made in firmware for peripheral_uart?

Since the overall power consumption of the nRF52832 is very low, I am not concerned with implementing sleep mode.

[Menon]

Hello,

Yes, you can use the internal RC oscillator instead of a 32 kHz crystal on a custom board made of nRF52832. I assume you are using our Nrf Connect SDK; if so, you need to include the below configuration inside the application. Read more about the below configuration inside the Kconfig references.

CONFIG_CLOCK_CONTROL=y  //  set the clock control to enabled
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y  //  set the clock control to enabled
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n // disable the external crystal oscillator

Kind Regards,

Abhijith

[bdoan]

Does it need to use any low frequency oscillator if sleep more is not required?

[Susheel Nuguru]

Hi, the RTC timers in the RTOS uses low frequency oscillator. This RTC is running even in sleep mode so you need this LF clock even in low power modes. It is very unlikely that you are designing something that does not use a peripheral that does not use a LF clock. so in short, you need either a external crystal or need to configure to use internal RC for LFCLK for your system to work.