nRF52 Bootloader

Features

• DFU over Serial and OTA ( application, Bootloader+SD )
• Self-upgradable via Serial and OTA
• DFU using UF2 (https://github.com/Microsoft/uf2) (application only)
• Auto-enter DFU briefly on startup for DTR auto-reset trick (832 only)

How to use

There are two pins, DFU and FRST that bootloader will check upon reset/power:

• Double Reset Reset twice within 500 ms will enter DFU with UF2 and CDC support (only works with nRF52840)
• DFU = LOW and FRST = HIGH: Enter bootloader with UF2 and CDC support
• DFU = LOW and FRST = LOW: Enter bootloader with OTA, to upgrade with a mobile application such as Nordic nrfConnect/Toolbox
• DFU = HIGH and FRST = HIGH: Go to application code if it is present, otherwise enter DFU with UF2
• The GPREGRET register can also be set to force the bootloader can enter any of above modes (plus a CDC-only mode for Arduino). GPREGRET is set by the application before performing a soft reset.

#include "nrf_nvic.h"
void reset_to_uf2(void) {
  NRF_POWER->GPREGRET = 0x57; // 0xA8 OTA, 0x4e Serial
  NVIC_SystemReset();         // or sd_nvic_SystemReset();
}

Please check the board definition for details.

Making your own UF2

To create your own UF2 DFU update image, simply use the Python conversion script on a .bin file or .hex file, specifying the family as 0xADA52840 (nRF52840)

nRF52840
uf2conv.py firmware.hex -c -f 0xADA52840

If using a .bin file with the conversion script you must specify application address with the -b switch, this address depend on the SoftDevice size/version e.g S140 v6 is 0x26000, v7 is 0x27000

nRF52840
uf2conv.py firmware.bin -c -b 0x26000 -f 0xADA52840

To create a UF2 image for bootloader from a .hex file using separated family of 0xd663823c

uf2conv.py bootloader.hex -c -f 0xd663823c

What's the difference between bin and hex?

Burn & Upgrade with pre-built binaries

You can burn and/or upgrade the bootloader with either a J-link or DFU (serial) to a specific pre-built binary version

Note: The bootloader can be downgraded. Since the binary release is a merged version of both bootloader and the Nordic SoftDevice, you can freely upgrade/downgrade to any version you like.

How to compile and build

Use J-Link to "unbrick" the device.

Build

git clone this repo
cd bootloader
git submodule update --init
make all

Flash

To flash the bootloader (without softdevice/mbr) using JLink:

make flash

If you are using pyocd as debugger, add FLASHER=pyocd to make command:

make FLASHER=pyocd flash

To upgrade the bootloader using DFU Serial via port /dev/ttyACM0

make SERIAL=/dev/ttyACM0 flash-dfu

make flash-sd  # flash SoftDevice (will erase chip)
make flash-mbr # flash mbr only

说明

make all 之后，写入 opensk.uf2

DCONFIG_GPIO_AS_PINRESET 被定义的时候， P0.18 会被当作 RESET

这个 P0.18 不能修改成别的 PIN