How to use internal capacitors on nrf5340?

RE: How to use internal capacitors on nrf5340?

Simon — Mon, 20 Jun 2022 14:43:32 GMT

Try adding these Kconfigs to the prj.conf:

CONFIG_SOC_ENABLE_LFXO=y
CONFIG_SOC_LFXO_CAP_INT_7PF=y
CONFIG_SOC_HFXO_CAP_INTERNAL=y
CONFIG_SOC_HFXO_CAP_INT_VALUE_X2=20
CONFIG_BUILD_WITH_TFM=y

Then build and program you application, and read the registers in the following manner:

@$ nrfjprog --memrd 0x400046D0
0x400046D0: 00000002 |....|

@$ nrfjprog --memrd 0x400045C4
0x400045C4: 00000107 |....|

Explanations:

[quote user="bong9"]I used the board name nrf5340dk_nrf5340_cpuapp_ns.
Was it a problem to use it as nonsecure?[/quote]

You need to add CONFIG_BUILD_WITH_TFM due to the following: https://github.com/nrfconnect/sdk-zephyr/blob/v2.7.99-ncs1-1/soc/arm/nordic_nrf/nrf53/Kconfig.soc#L149

[quote user="bong9"]Cannot read as nrfjprog --memrd.[/quote]

Be aware that the nonsecure oscillator offset is 0x40004000, not 0x50004000. This is probably why you couldn't read the registers

Best regards,

Simon

RE: How to use internal capacitors on nrf5340?

noseed — Fri, 17 Jun 2022 13:46:33 GMT

Hi.

I used the board name nrf5340dk_nrf5340_cpuapp_ns.
Was it a problem to use it as nonsecure?
Cannot read as nrfjprog --memrd.

The reason for 7 is that I checked the link below to add 3pf.

link

Thank you.

RE: How to use internal capacitors on nrf5340?

Simon — Fri, 17 Jun 2022 13:10:48 GMT

I did some testing.

I programmed the hello world sample (NCS v1.9.1) to the nRF5340 DK using the board name nrf5340dk_nrf5340_cpuapp with the following prj.conf

CONFIG_SOC_ENABLE_LFXO=y
CONFIG_SOC_LFXO_CAP_INT_7PF=y
CONFIG_SOC_HFXO_CAP_INTERNAL=y
CONFIG_SOC_HFXO_CAP_INT_VALUE_X2=20

Then I read the XOSC32KI.INTCAP register:

@$ nrfjprog --memrd 0x500046D0
0x500046D0: 00000002 |....|

According to the documentation, it is correct. A value of 2 means the 7 pF internal load capacitance is selected

Then I put a break point in the function nordicsemi_nrf53_init() to see what the calculated cap value was, which was 7
- I don't have much knowledge about this topic, so I'm not sure if a value of 7 makes sense. If it doesn't please let me know and I will take a closer look at it/ask internally
Then I read the XOSC32MCAPS register:

@$ nrfjprog --memrd 0x500045C4
0x500045C4: 00000107 |....|

As you can see, this will enable the capacitor and set the cap value to 7

Best regards,

Simon