Does nrf52820 support USB DFU？

[helen]

Excuse me：

                   1、 I can't find the USB DFU example of the nrf52820 in the SDK.Does nrf52820 support USB DFU？

                  2、52820 needs to Implement USB OTA ，enumeration as keyboard, mouse and 2.4G wireless communication. Please help to evaluate whether the resources are enough?

Thanks！

[Einar Thorsrud]

Hi,

The statement you refer to is old, from when the nRF52840 was the only nRF52 series device with USB, but has unfortunately not been updated. There is nothing preventing you from using USB DFU on the nRF52820. There is also example projects for this in the SDK, under <SDK17.0.2>\examples\dfu\secure_bootloader\pca10100e_usb*. Note that these projects are using nRF52820 emulation on the nRF52833 DK.

[helen]

Is there a USB DFU Application guide for nrf52820? Where can I get the USB DFU Application guide?

[Einar Thorsrud]

Hi,

I am not sure what you mean by Application guide?

What we have is the Open Bootloader with DFU example which demonstrates USB bootloader, although not with project files for the nRF52820 (those are only provided for the secure bootloader, but both can be referred to to see how to make a USB bootloader for the nRF52820. You can also refer to the documentation for the bootloader modules including the DFU trigger library.

[helen]

Excuse me

1、How much flash does the bootloader occupy in this example（<SDK17.0.2>\examples\dfu\secure_bootloader\pca10100e_usb）?After compiling this project, I see that there is not much flash available.

2、How much flash and ram do S132 and S112 occupy respectively?

[Einar Thorsrud]

Hi,

The memory usage you see in SES there is misleading, as it includes the reserved flash. You will get a better overview if you click View -> Memory Usage, and expand FLASH:

Here you see that address 0 - 0x33FFF is reserved (this is where you would have the MBR/SoftDevice, application, etc). The bootloader itself is close to the end, but there are two pages resaved after that for MBR parameters and bootloader settings. You can also see the start address of the bootloader in the linker settings, and for the <SDK17.0.2>\examples\dfu\secure_bootloader\pca10100e_usb project this is 0x34000. The size of this bootloader is 33.2 kB, but as it requires full pages in practice it is 36 kB (0x9000 bytes).

The SoftDevice sizes can be found from the SoftDevice specification. For S132 7.2.0 the size is 152 kB (0x26000 bytes). And for S112 7.2.0 it is 100.0 kB (0x19000 bytes). Note that you can always find this information in the release notes of the SoftDevice.