nrf52840 configuration and Antenna design for custom board

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Thu, 24 Jun 2021 14:00:19 GMT

We recommend that total sink + source is <15mA. This will ensure that the chip can still use do all internal operations (e.g. radio) without reduction in performance.

If you draw less than min IOH,HDH = 6mA, then the output pin voltage will be (if VDD>=2.7V) >VDD-0.4V. And if you draw less than IOL,HDH = 3mA, then the output pin voltage will be (if VDD>=1.7V) >VDD-0.4V. If you draw more than this, then we don't guarantee >VDD-0.4V.

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Fri, 11 Jun 2021 05:00:57 GMT

Thanks for the help. I have another question. I was reading about GPIO current specification in product specification document. We can source/sink 15 mA current in GPIOs configured in high drive mode. We can source/sink upto 4 mA from GPIO configured in normal drive mode. If we configure GPIO in high drive mode and source current of 15 mA from it can we source 4 mA from other GPIOs that are configured in low drive mode?
What is total current we can source/sink from all GPIOs?

Regards

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Wed, 09 Jun 2021 11:25:49 GMT

At any voltage level.

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Tue, 08 Jun 2021 11:22:56 GMT

I am reading product specifications for nrf52840. In section 5.3.8.2 Regulator specifications, REG0 stage. The max current reading of 25 mA are at which voltage level of High voltage mode because high voltage mode can be from 2.5 V to 5.5 V

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Mon, 07 Jun 2021 12:43:56 GMT

Yes

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Mon, 07 Jun 2021 11:07:55 GMT

Thanks for the reply so just to confirm for debugging nrf52840 DK we do not need any external debugging device. The jlink on board on DK is enough

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Mon, 07 Jun 2021 08:15:38 GMT

1. The DK comes with a debugger / programmer already https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/if_mcu.html

2. Take a look at this: https://infocenter.nordicsemi.com/topic/nwp_027/WP/nwp_027/intro.html

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Mon, 07 Jun 2021 05:39:15 GMT

I have couple of more questions:

1) We are using nrf52840 DK for developing our firmware. I want to ask do we need external debugger like Jlink debbuger ultra plus for debugging nrf52840 DK?

2) We will expose SWD interface in our custom board can you recommend device that we can use for production programing?

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Fri, 04 Jun 2021 13:43:53 GMT

Thankyou

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Fri, 04 Jun 2021 11:58:06 GMT

Other than general ESD protection. SWDIO has internal pullup, SWDCLK has internal pulldown. In case these aren't sufficient, it's a good ideal to at least have space for external resistors to make the design more tolerant against noise.

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Fri, 04 Jun 2021 11:54:16 GMT

Thanks

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Fri, 04 Jun 2021 11:51:25 GMT

You can just remove the connector. No need for a resistor here. For measurements on the radio or the antenna, just cut the track and solder the coax to the ground plane / track.

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Fri, 04 Jun 2021 09:57:38 GMT

I have another question if I want to expose the SWD interface of nrf52840 and I am powering the custom board with battery what care should I take?
If you can refer me to some document that I can see for reference?

RE: nrf52840 configuration and Antenna design for custom board

Moghees — Fri, 04 Jun 2021 09:55:19 GMT

Thanks and If I remove the RF connector shown in blue box will there be any problem?
or
Should I place 0R resistor in place of it?

RE: nrf52840 configuration and Antenna design for custom board

ketiljo — Fri, 04 Jun 2021 08:50:54 GMT

Yes, the NCF pins can be left floating as any other GPIO not in use.

For the RF section, you can use the DK antenna and matching network. Note how C3 is grounded.