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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:

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.

IMPORTANT: Disable Mass Storage on PCA10056 J-Link

The J-Link firmware on the PCA10056 implement USB Mass Storage, but this causes a known conflict with reliable USB CDC serial port communication. In order to use the serial bootloader, you must disable MSD support on the Segger J-Link!

To disable mass storage support, run the JLinkExe (or equivalent) command, and send MSDDisable. (You can re-enable MSD support via MSDEnable):

$ JLinkExe
SEGGER J-Link Commander V6.20f (Compiled Oct 13 2017 17:20:01)
DLL version V6.20f, compiled Oct 13 2017 17:19:52

Connecting to J-Link via USB...O.K.
Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Jul 24 2017 17:30:12
Hardware version: V1.00
S/N: 683947110
VTref = 3.300V


Type "connect" to establish a target connection, '?' for help
J-Link>MSDDisable
Probe configured successfully.
J-Link>exit

Building and Flashing CircuitPython

Installing `nrfutil`

If you haven't installed the required command-line tool yet, go to the /libs/nrfutil folder (where nrfutil 0.5.2b is installed as a sub-module) and run the following commands:

If you get a 'sudo: pip: command not found' error running 'sudo pip install', you can install pip via 'sudo easy_install pip'

$ cd ../../lib/nrfutil
$ sudo pip install -r requirements.txt
$ sudo python setup.py install

Changes to `nrfutil` in 0.5.2b

IMPORTANT: Make sure that you have version 0.5.2b, since a small change was required to dfu_transport_serial.py to account for the increased minimum flash erase time on the nRF52840 compared to the earlier nRF52832!

You can also manually change the file with the following new values (lines 67-68), and reinstall the utility via sudo python setup.py install:

FLASH_PAGE_ERASE_MAX_TIME = 0.1      # Worst time to erase a page 100 ms
FLASH_PAGE_ERASE_MIN_TIME = 0.09      # Best time to erase a page 90 ms

Flashing CircuitPython

With the serial bootloader present on your board, you first need to force your board into DFU mode by holding down BUTTON1 and RESETTING the board (with BUTTON1 still pressed as you come out of reset).

This will give you a fast blinky DFU pattern to indicate you are in DFU mode.

At this point, you can build and flash a CircuitPython binary via the following command:

$ make V=1 SD=s140 SERIAL=/dev/tty.usbmodem1411 BOARD=feather52840 dfu-gen dfu-flash

This should give you the following results:

$ make V=1 SD=s140 SERIAL=/dev/tty.usbmodem1411 BOARD=feather52840 dfu-gen dfu-flash
nrfutil dfu genpkg --sd-req 0xFFFE --dev-type 0x0052 --application build-feather52840-s140/firmware.hex build-feather52840-s140/dfu-package.zip
Zip created at build-feather52840-s140/dfu-package.zip
nrfutil --verbose dfu serial --package build-feather52840-s140/dfu-package.zip -p /dev/tty.usbmodem1411 -b 115200
Upgrading target on /dev/tty.usbmodem1411 with DFU package /Users/kevintownsend/Dropbox/microBuilder/Code/CircuitPython/circuitpython-mb/ports/nrf/build-feather52840-s140/dfu-package.zip. Flow control is disabled.
Starting DFU upgrade of type 4, SoftDevice size: 0, bootloader size: 0, application size: 195252
Sending DFU start packet
Sending DFU init packet
Sending firmware file
################################################################################################################################################################################################################################################################################################################################################################################################
Activating new firmware

DFU upgrade took 41.6610329151s
Device programmed.

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