circuitpython/ports/nrf

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
• nRF52840
  • PCA10056

Compile and Flash

Prerequisite steps for building the nrf port:

git clone <URL>.git micropython
cd micropython
git submodule update --init
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
make flash

Alternatively the target board could be defined:

 make BOARD=pca10040
 make BOARD=pca10040 flash

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

Enable MICROPY_FATFS

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_FATFS 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 and MICROPY_VFS_FAT in mpconfigport.h.

For example:

 make BOARD=pca10040 MICROPY_FATFS=1

Target Boards and Make Flags

Target Board (BOARD)	Bluetooth Stack (SD)	Bluetooth Support	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
pca10056	s140	Peripheral and Central	Segger

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

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.