micropython/ports/nrf/README.md

MicroPython Port To The Nordic Semiconductor nRF Series

This is a port of MicroPython to the Nordic Semiconductor nRF series of chips.

Supported Features

• UART
• SPI
• LEDs
• Pins
• ADC
• I2C
• PWM (nRF52 only)
• Temperature
• RTC (Real Time Counter. Low-Power counter)
• BLE support including:
  • Peripheral role on nrf51 targets
  • Central role and Peripheral role on nrf52 targets
  • REPL over Bluetooth LE (optionally using WebBluetooth)
  • ubluepy: Bluetooth LE module for MicroPython
  • 1 non-connectable advertiser while in connection

Tested Hardware

• nRF51
  • micro:bit
  • PCA10000 (dongle)
  • PCA10001
  • PCA10028
  • PCA10031 (dongle)
  • WT51822-S4AT
• nRF52832
  • PCA10040
  • Adafruit Feather nRF52
  • Thingy:52
  • Arduino Primo
  • IBK-BLYST-NANO breakout board
  • BLUEIO-TAG-EVIM BLYST Nano Sensor board
  • uBlox EVK-NINA-B1
• nRF52840
  • PCA10056
  • PCA10059
  • Particle Xenon
  • nRF52840 MDK USB Dongle
• nRF9160
  • PCA10090
  • Actinius Icarus

Compile and Flash

Prerequisite steps for building the nrf port:

git clone <URL>.git micropython
cd micropython
make -C mpy-cross

By default, the PCA10040 (nrf52832) is used as compile target. To build and flash issue the following command inside the ports/nrf/ folder:

make submodules
make
make deploy

Alternatively the target board could be defined:

make submodules
make BOARD=pca10040
make BOARD=pca10040 deploy

Compile without LTO enabled

As a space optimization, LTO (Link Time Optimization) has been enabled on all targets in the nrf-port. The -flto linker flag can be toggled easily by using the argument LTO when building. The example below shows how to disable LTO for the compilation:

make BOARD=pca10040 LTO=0

Note: There have been several issues with use of LTO in conjunction with GNU ARM Embedded Toolchain 7.2.1/4Q17. It's recommended to use a toolchain after this release, for example 7.3.1/2Q18 or 8.2.1/4Q18. The alternative would be to build the target using the LTO=0 as described above.

Compile and Flash with Bluetooth Stack

First prepare the bluetooth folder by downloading Bluetooth LE stacks and headers:

 ./drivers/bluetooth/download_ble_stack.sh

If the Bluetooth stacks has been downloaded, compile the target with the following command:

make BOARD=pca10040 SD=s132

The make sd will trigger a flash of the bluetooth stack before that application is flashed. Note that make sd will perform a full erase of the chip, which could cause 3rd party bootloaders to also be wiped.

make BOARD=pca10040 SD=s132 sd

Note: further tuning of features to include in bluetooth or even setting up the device to use REPL over Bluetooth can be configured in the bluetooth_conf.h.

Compile with frozen modules

Frozen modules are Python modules compiled to bytecode and added to the firmware image, as part of MicroPython. They can be imported as usual, using the import statement. The advantage is that frozen modules use a lot less RAM as the bytecode is stored in flash, not in RAM like when importing from a filesystem. Also, frozen modules are available even when no filesystem is present to import from.

To use frozen modules, put them in a directory (e.g. freeze/) and supply make with the given directory. For example:

 make BOARD=pca10040 FROZEN_MPY_DIR=freeze

Compile with freeze manifest

Freeze manifests can be used by definining FROZEN_MANIFEST pointing to a manifest.py. This can either be done by a make invocation or by defining it in the specific target board's mpconfigboard.mk.

For example:

make BOARD=pca10040 FROZEN_MANIFEST=path/to/manifest.py

In case of using the target board's makefile, add a line similar to this:

FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest.py

In these two examples, the manual make invocation will have precedence.

Enable MICROPY_VFS_FAT

As the oofatfs module is not having header guards that can exclude the implementation compile time, this port provides a flag to enable it explicitly. The MICROPY_VFS_FAT is by default set to 0 and has to be set to 1 if oofatfs files should be compiled. This will be in addition of setting MICROPY_VFS in mpconfigport.h.

For example:

 make BOARD=pca10040 MICROPY_VFS_FAT=1

Enable MICROPY_VFS_LFS1 or MICROPY_VFS_LFS2

In order to enable littlefs as device flash filesystem, MICROPY_VFS_LFS1 or MICROPY_VFS_LFS2 can be set. This will be in addition of setting MICROPY_VFS in mpconfigport.h or mpconfigboard.h.

For example:

make BOARD=pca10056 MICROPY_VFS_LFS2=1

Set file system size

The size of the file system on the internal flash is configured by the linker script parameter _fs_size. This can either be overriden by the linker script or dynamically through the makefile. By seting a value to the FS_SIZE. The number will be passed directly to the linker scripts in order to calculate the start and end of the file system. Note that the parameter value must be in linker script syntax as it is passed directly.

For example, if we want to override the default file system size set by the linker scripts to use 256K:

make BOARD=pca10056 MICROPY_VFS_LFS2=1 FS_SIZE=256K

Also note that changing this size between builds might cause loss of files present from a previous firmware as it will format the file system due to a new location.

Target Boards and Make Flags

Target Board (BOARD)	Bluetooth Stack (SD)	Bluetooth Support	Bootloader	Default Flash Util
microbit	s110	Peripheral		PyOCD
pca10000	s110	Peripheral		Segger
pca10001	s110	Peripheral		Segger
pca10028	s110	Peripheral		Segger
pca10031	s110	Peripheral		Segger
wt51822_s4at	s110	Peripheral		Manual, see datasheet for pinout
pca10040	s132	Peripheral and Central		Segger
feather52	s132	Peripheral and Central		Manual, SWDIO and SWCLK solder points on the bottom side of the board
arduino_primo	s132	Peripheral and Central		PyOCD
ibk_blyst_nano	s132	Peripheral and Central		IDAP
idk_blyst_nano	s132	Peripheral and Central		IDAP
blueio_tag_evim	s132	Peripheral and Central		IDAP
evk_nina_b1	s132	Peripheral and Central		Segger
pca10056	s140	Peripheral and Central		Segger
pca10059	s140	Peripheral and Central	OpenBootloader	nrfutil
particle_xenon	s140	Peripheral and Central		Black Magic Probe
nrf52840-mdk-usb-dongle	s140	Peripheral and Central	OpenBootloader	nrfutil
pca10090	None (bsdlib.a)	None (LTE/GNSS)		Segger
actinius_icarus	None (bsdlib.a)	None (LTE/GNSS)		Segger

IDAP-M/IDAP-Link Targets

Install the necessary tools to flash and debug using IDAP-M/IDAP-Link CMSIS-DAP Debug JTAG:

IDAPnRFProg for Linux IDAPnRFProg for OSX IDAPnRFProg for Windows

Segger Targets

Install the necessary tools to flash and debug using Segger:

JLink Download

nrfjprog Download

note: On Linux it might be required to link SEGGER's libjlinkarm.so inside nrfjprog's folder.

PyOCD/OpenOCD Targets

Install the necessary tools to flash and debug using OpenOCD:

sudo apt-get install openocd
sudo pip install pyOCD

Black Magic Probe Targets

This requires no further dependencies other than arm-none-eabi-gdb.

make deploy will use gdb to load and run new firmware. See this guide for more tips about using the BMP with GDB.

nRFUtil Targets

Install the necessary Python packages that will be used for flashing using the bootloader:

sudo pip install nrfutil
sudo pip install intelhex

The intelhex provides the hexmerge.py utility which is used by the Makefile to trim of the MBR in case SoftDevice flashing is requested.

nrfutil as flashing backend also requires a serial port paramter to be defined in addition to the deploy target of make. For example:

make BOARD=nrf52840-mdk-usb-dongle NRFUTIL_PORT=/dev/ttyACM0 deploy

If the target device is connected to /dev/ttyACM0 serial port, the NRFUTIL_PORT parameter to make can be elided as it is the default serial port set by the Makefile.

When enabling Bluetooth LE, as with the other flash utils, the SoftDevice needs to be flashed in the first firmware update. This can be done by issuing the sd target instead of deploy. For example:

make BOARD=nrf52840-mdk-usb-dongle SD=s140 NRFUTIL_PORT=/dev/ttyACM0 sd

Bluetooth LE REPL

The port also implements a BLE REPL driver. This feature is disabled by default, as it will deactivate the UART REPL when activated. As some of the nRF devices only have one UART, using the BLE REPL free's the UART instance such that it can be used as a general UART peripheral not bound to REPL.

The configuration can be enabled by editing the bluetooth_conf.h and set MICROPY_PY_BLE_NUS to 1.

When enabled you have different options to test it:

• NUS Console for Linux (recommended)
• WebBluetooth REPL (experimental)

Other:

• nRF UART application for IPhone/Android

WebBluetooth mode can also be configured by editing bluetooth_conf.h and set BLUETOOTH_WEBBLUETOOTH_REPL to 1. This will alternate advertisement between Eddystone URL and regular connectable advertisement. The Eddystone URL will point the phone or PC to download WebBluetooth REPL (experimental), which subsequently can be used to connect to the Bluetooth REPL from the PC or Phone browser.

Pin numbering scheme for nrf52840-based boards

Software Pins 0-31 correspond to physical pins 0.x and software Pins 32-47 correspond to physical pins 1.x.

Example: Pin(47) would be 1.15 on the PCA10059