CircuitPython Port To The Nordic Semiconductor nRF52 Series

This is a port of CircuitPython to the Nordic Semiconductor nRF52 series of chips.

Supported Features

  • UART
  • SPI
  • LEDs
  • Pins
  • ADC
  • I2C
  • PWM
  • Temperature
  • RTC (Real Time Counter. Low-Power counter)
  • BLE support including:
    • Peripheral role
    • Scanner role
    • REPL over Bluetooth LE (optionally using WebBluetooth)
    • ubluepy: Bluetooth LE module for CircuitPython
    • 1 non-connectable advertiser while in connection

Tested Hardware

Compile and Flash

Prerequisite steps for building the nrf port:

git clone <URL>.git circuitpython
cd circuitpython
git submodule update --init
make -C mpy-cross

By default, the feather52 (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=pca10056
 make flash

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.

Target Boards and Make Flags

Target Board (BOARD) | Bluetooth Stack (SD) | Bluetooth Support | Flash Util ———————|————————-|————————|——————————- pca10040 | s132 | Peripheral and Scanner | Segger feather52 | s132 | Peripheral and Scanner | UART DFU pca10056 | s140 | Peripheral and Scanner | Segger

Segger Targets

Install the necessary tools to flash and debug using Segger:

JLink Download

nrfjprog linux-32bit Download

nrfjprog linux-64bit Download

nrfjprog osx Download

nrfjprog win32 Download

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

DFU Targets

sudo apt-get install build-essential libffi-dev pkg-config gcc-arm-none-eabi git python python-pip
git clone https://github.com/adafruit/Adafruit_nRF52_Arduino.git
cd Adafruit_nRF52_Arduino/tools/nrfutil-0.5.2/
sudo pip install -r requirements.txt
sudo python setup.py install

make flash and make sd will not work with DFU targets. Hence, dfu-gen and dfu-flash must be used instead.

  • dfu-gen: Generates a Firmware zip to be used by the DFU flash application.
  • dfu-flash: Triggers the DFU flash application to upload the firmware from the generated Firmware zip file.

Example on how to generate and flash feather52 target:

make BOARD=feather52 SD=s132
make BOARD=feather52 SD=s132 dfu-gen
make BOARD=feather52 SD=s132 dfu-flash

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:

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.