circuitpython/ports/nrf/boards/feather52840/README.md

# Setup

The `feather52840` board is currently based on the `PCA10056` development
board from Nordic Semiconductors, since commercial modules are not yet
available for the nRF52840.

The difference between the `pca10056` and `feather52840` board support
packages is that no bootloader is present on the `pca10056` (a HW debugger
like a Segger J-Link is required to flash firmware images), whereas the
`feather52840` package uses a serial bootloader, with a slightly different
flash layout to account for the bootloader's presence.

Both targets run on the same hardware and assume the same pinouts.

The `feather52840` board support package will be updated at a later date
to reflect any pin changes in the final Feather form-factor HW.

## Installing CircuitPython submodules

Before you can build, you will need to run the following commands once, which
will install the submodules that are part of the CircuitPython ecosystem, and
build the `mpy-cross` tool:

```
$ cd circuitpython
$ git submodule update --init
$ make -C mpy-cross
```

You then need to download the SD and Nordic SDK files via:

> This script relies on `wget`, which must be available from the command line.

```
$ cd ports/nrf
$ ./drivers/bluetooth/download_ble_stack.sh
```

## Installing the Serial Bootloader

The Adafruit nRF52840 Feather uses a serial bootloader that allows you to
update the core CircuitPython firmware and internal file system contents
using only a serial connection.

On empty devices, the serial bootloader will need to be flashed once using a
HW debugger such as a Segger J-Link before the serial updater (`nrfutil`) can
be used.

### Install `nrfjprog`

Before you can install the bootloader, you will first need to install the
`nrfjprog` tool from Nordic Semiconductors for your operating system. The
binary files can be downloaded via the following links:

- [nRF5x toolset tar for Linux 32-bit v9.7.2](http://www.nordicsemi.com/eng/nordic/Products/nRF52832/nRF5x-Command-Line-Tools-Linux32/52619)
- [nRF5x toolset tar for Linux 64-bit v9.7.2](http://www.nordicsemi.com/eng/nordic/Products/nRF52832/nRF5x-Command-Line-Tools-Linux64/51388)
- [nRF5x toolset tar for OSX v9.7.2](http://www.nordicsemi.com/eng/nordic/Products/nRF52832/nRF5x-Command-Line-Tools-OSX/53406)
- [nRF5x toolset installer for Windows v9.7.2](http://www.nordicsemi.com/eng/nordic/Products/nRF52832/nRF5x-Command-Line-Tools-Win32/48768)

You will then need to add the `nrfjprog` folder to your system `PATH` variable
so that it is available from the command line. The exact process for this is
OS specific, but on a POSIX type system like OS X or Linux, you can
temporarily add the location to your `PATH` environment variables as follows:

```
$ export PATH=$PATH:YOURPATHHERE/nRF5x-Command-Line-Tools_9_7_2_OSX/nrfjprog/
```

You can test this by running the following command:

```
$ nrfjprog --version
nrfjprog version: 9.7.2
JLinkARM.dll version: 6.20f
```

### Flash the Bootloader with `nrfjprog`

> This operation only needs to be done once, and only on boards that don't
  already have the serial bootloader installed.

Once `nrfjprog` is installed and available in `PATH` you can flash your
board with the serial bootloader via the following command:

```
make SD=s140 BOARD=feather52840 boot-flash
```

This should give you the following (or very similar) output, and you will see
a DFU blinky pattern on one of the board LEDs:

```
$ make SD=s140 BOARD=feather52840 boot-flash
Use make V=1, make V=2 or set BUILD_VERBOSE similarly in your environment to increase build verbosity.
nrfjprog --program boards/feather52840/bootloader/feather52840_bootloader_6.0.0_s140_single.hex -f nrf52 --chiperase --reset
Parsing hex file.
Erasing user available code and UICR flash areas.
Applying system reset.
Checking that the area to write is not protected.
Programing device.
Applying system reset.
Run.
```

From this point onward, you can now use a simple serial port for firmware
updates.

## Building and Flashing CircuitPython

With the serial bootloader present on your board, you can build and flash
a CircuitPython binary via the following command:

```
make SD=s140 SERIAL=/dev/ttyACM0 BOARD=feather52840 dfu-gen dfu-flash
```