NRF52840 boot/flash strategy

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Tue, 08 Jan 2019 08:54:11 GMT

Does not seem so unfortunately (link 1, link 2).

RE: NRF52840 boot/flash strategy

Garrett — Fri, 04 Jan 2019 19:54:40 GMT

So booting directly from external flash via XIP is not an option?

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Tue, 23 Jan 2018 12:21:26 GMT

Great! Thanks. :) Good luck with your future development if you decide to use the nrf52840!

RE: NRF52840 boot/flash strategy

Mickael — Tue, 23 Jan 2018 12:07:12 GMT

Very happy with the support! Thanks a lot Bjorn.

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Tue, 23 Jan 2018 11:54:13 GMT

If you are happy with the answers, would you mind pressing the up arrow on some of my comments? :)

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Tue, 23 Jan 2018 11:52:37 GMT

If the nrf52 bootloader gets corrupted, you can reprogram the nrf52 bootloader on the nrf52840 PDK via the built in Segger J-Link programmer using just a usb cable. If the bootloader on an external nrf52840 gets corrupt, you can then only program the external chip using a Segger J-Link programmer either on the nrf52dk and debug out (see link), or with another segger j-link programmer. You will have to use a 10 pin SWD cable for this.

RE: NRF52840 boot/flash strategy

Mickael — Fri, 19 Jan 2018 14:30:02 GMT

Thanks again!

And I promise this is the last one:

so if your bootloader in flash gets corrupted, the ONLY way you re-program an NRF52840 (on the DK or on our own product) is via JTAG or SWD?

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Fri, 19 Jan 2018 13:46:40 GMT

The nrf52840 pdk has an IF BOOT/RESET button that can be used to update the Segger chip on the PDK. This way, the interface MCU on the PDK enters bootloader mode. You are correct that the bootloader is purely in flash. Yep, what dfu is chosen is purely down to what is coded in the bootloader. See this link here for more info.

RE: NRF52840 boot/flash strategy

Mickael — Thu, 18 Jan 2018 17:27:36 GMT

Hi Bjorn,

I have almost got it now (I think!).

... But I have got one last one:

often MCUs has a specific "bootstrap" pin, which can be set before device start-up and that will force ROM Code to jump to a minimal DFU code which can be used to reprogram via a hardcoded specific interface. This is used, for example, if your flash is corrupted (included your bootloader) and your device wont boot anymore... Well anyway I am sure that you know all of this.
so far as I can tell, NRF52 does not implement such an HW level mechanism - ist that correct?
My current understanding of NRF52840 mechanism is that the bootloard is purely in Flash - what DFU is chosen is purely down to what is coded in the bootloader - right?

Thanks for your help, Mickael

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Wed, 17 Jan 2018 09:55:59 GMT

The device that is referred to in the Serial Secure DFU bootloader example can refer to either the nrf52DK or the nrf52 chip. Since the USB DFU example implementation also uses the serial secure dfu bootloader, it will be the same for this example. In general, Nordic recommends to start developing a product on the nrf52dk & then move on to a custom board once the application works on the DK.

RE: NRF52840 boot/flash strategy

Mickael — Tue, 16 Jan 2018 11:14:03 GMT

Hi Bjorn,

thanks a lot for your answer - I am starting to see clearer.

Can you therefore confirm my understanding below:

If looking at NRF52840 chip physical interfaces (as opposed to the DK's), the FW can be programmed via: SWD (directly using a J-Link or via P19 of the NRF52 DK thanks to the embedded J-LINK OB) ; BLE (as you mentionned) ; on the NRF52 DK documentation, I have also found evidences of UART and USB DFUs implementation but I am struggling to understand if they refer to the DK's board or the NRF's chip interfaces... Could you please clarify that for me?

Thanks for your help, Mickael

RE: NRF52840 boot/flash strategy

Bjørn Kvaale — Mon, 15 Jan 2018 15:02:31 GMT

Take a look at these two links (link1, link2). The recommended ways are to either use the debug out port on an nrf52 dk (p19) & program the external module via an SWD cable or via P20 to program shield-mounted targets. This can be done via nrfgostudio for example. For an example of Over the Air DFU via BLE, you can have a look at this secure dfu blog post. If your device has a USB connected to Segger J-Link (like the nrf52 DK), you could naturally also use USB.