# Adafruit nRF52 Bootloader

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This is a CDC/DFU/UF2 bootloader for nRF52 boards.

- [Adafruit CLUE](https://www.adafruit.com/product/4500)
- [Adafruit Circuit Playground Bluefruit](https://www.adafruit.com/product/4333)
- [Adafruit Feather nRF52832](https://www.adafruit.com/product/3406)
- [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062)
- [Adafruit Feather nRF52840 Sense](https://www.adafruit.com/product/4516)
- [Adafruit ItsyBitsy nRF52840 Express](https://www.adafruit.com/product/4481)
- Adafruit Metro nRF52840 Express
- [Electronut Labs Papyr](https://docs.electronut.in/papyr/)
- MakerDiary MDK nRF52840 USB Dongle
- [Nordic nRF52840DK PCA10056](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK)
- [Nordic nRF52840DK PCA10059 ("Dongle")](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-Dongle)
- Particle Argon
- Particle Boron
- Particle Xenon

UF2 is an easy-to-use bootloader that appears as a flash drive. You can just copy `.uf2`-format
application images to the flash drive to load new firmware.
See https://github.com/Microsoft/uf2 and https://github.com/adafruit/uf2-samdx1
for more information.

[adafruit-nrfutil](https://github.com/adafruit/Adafruit_nRF52_nrfutil),
a modified version of [Nordic nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil),
is required to perform DFU.
Install `python3` if it is not installed already and run this command to install adafruit-nrfutil from PyPi:

```
$ pip3 install --user adafruit-nrfutil
```

This repository depends on the following submodules:

- [tinyusb](https://github.com/hathach/tinyusb)
- [nrfx](https://github.com/NordicSemiconductor/nrfx)

Note that `tinyusb` also includes `nrfx` as a submodule, so you need
to initialize and update  submodules with the `--recursive`` flag.

Clone this repo with following commands, or fork it for your own development

```
git clone https://github.com/adafruit/Adafruit_nRF52_Bootloader
cd Adafruit_nRF52_Bootloader
git submodule update --init --recursive
```

## 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 = LOW`: Factory Reset mode: erase firmware application and its data
- `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.

On the Nordic PCA10056 DK board, `DFU` is connected to **Button1**, and `FRST` is connected to **Button2**.
So holding down **Button1** while clicking **RESET** will put the board into USB bootloader mode, with UF2 and CDC support.
Holding down **Button2** while clicking **RESET** will put the board into OTA (over-the-air) bootloader mode.

On the Nordic PCA10059 Dongle board, `DFU` is connected to the white button.
`FRST` is connected to pin 1.10. Ground it to pull `FRST` low, as if you had pushed an `FRST`  button.
There is an adjacent ground pad.

For other boards, 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](https://github.com/Microsoft/uf2/blob/master/utils/uf2conv.py) on a .bin file or .hex file, specifying the family as **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 

To create a UF2 image from a .bin file:
```
uf2conv.py firmware.bin -c -b 0x26000 -f 0xADA52840
```

To create a UF2 image from a .hex file:
```
uf2conv.py firmware.hex -c -f 0xADA52840
```

## 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
without the hassle of installing a toolchain and compiling the code.
This is preferred if you are not developing/customizing the bootloader.
Pre-builtin binaries are available on GitHub [releases](https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases)

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

You should only continue if you are looking to develop bootloader for your own.
You must have have a J-Link available to "unbrick" your device.

Prerequisites

- ARM GCC
- Nordic's [nRF5x Command Line Tools](https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Command-Line-Tools)

To build:

```
make BOARD=feather_nrf52840_express all
```

To flash the bootloader with JLink:

```
make BOARD=feather_nrf52840_express flash
```

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

```
make BOARD=feather_nrf52840_express SERIAL=/dev/ttyACM0 dfu-flash
```

To flash SoftDevice (and chip erase):

```
make BOARD=feather_nrf52840_express sd
```

For the list of supported boards, run `make` without `BOARD=` :

```
$ make
You must provide a BOARD parameter with 'BOARD='
Supported boards are: feather_nrf52840_express feather_nrf52840_express pca10056
Makefile:90: *** BOARD not defined.  Stop
```

### Common makefile problems

#### 1. `arm-none-eabi-gcc`: No such file or directory

If you get the following error ...

```
$ make BOARD=feather_nrf52840_express all 
Compiling file: main.c
/bin/sh: /usr/bin/arm-none-eabi-gcc: No such file or directory
make: *** [_build/main.o] Error 127
```

... you may need to pass the location of the GCC ARM toolchain binaries to `make` using
the variable `CROSS_COMPILE` as below:
```
$ make CROSS_COMPILE=/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/arm-none-eabi- BOARD=feather_nrf52832 all
```

#### 2. `mergehex: No such file or directory`

Make sure that `mergehex` is available from the command-line. This binary is
part of Nordic's nRF5x Command Line Tools.

#### 3. `make: nrfjprog: No such file or directory`

Make sure that `nrfjprog` is available from the command-line. This binary is
part of Nordic's nRF5x Command Line Tools.