Yunjia NRF51822

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Support for the Yunjia NRF51822 board

When using this board with RIOT, set the BOARD variable to yunjia-nrf51822 in your Makefile. If you follow the standard RIOT project structure, your Makefile should look like this:

# name of your application
APPLICATION = hello-world

# Change this to your board if you want to build for a different board
BOARD ?= yunjia-nrf51822

# This has to be the absolute path to the RIOT base directory:
RIOTBASE ?= $(CURDIR)/RIOT

include $(RIOTBASE)/Makefile.include

Support for the Yunjia NRF51822 board

Overview

The NRF51822 module by Yunjia Technology is a minimalistic but very low- priced module utilizing Nordics NRF51822QFAA SoC. The SoC features 16Kb of RAM, 256Kb of flash ROM and apart of the usual microcontroller peripherals with a 2.4GHz radio that supports both Nordics proprietary ShockBurst as well as Bluetooth Low Energy (BLE).

The board is available for example on ebay or Aliexpress for around 8-10 USD.

Hardware

yunjia-nrf51822

MCU	NRF51822QFAA
Family	ARM Cortex-M0
Vendor	Nordic Semiconductor
RAM	16Kb
Flash	256Kb
Frequency	16MHz
FPU	no
Timers	3 (2x 16-bit, 1x 32-bit [TIMER0])
ADCs	1x 10-bit (8 channels)
UARTs	1
SPIs	2
I2Cs	2
Vcc	1.8V - 3.6V
Datasheet	Datasheet
Reference Manual	Reference Manual

Flashing and Debugging

The Yunjia NRF51822 module comes without any on-board programming and flashing capabilities. It can be programmed using of-the-shelf programmers such as Segger’s JLink or STM’s STLink.

A very simple and affordable way to program and debug the Yunjia module is to use the integrated ST-Link/V2 programmer of most STM32 development board. The required steps are described in the following sections. If you want to use a standalone ST-Link adapter, you just simply have to alter the wiring to fit for your programmer, the software part is identical.

Hardware

If you are using an STM32 discovery board, you have to enable the standalone ST-Link mode by removing the two CN2 jumpers, found somewhere in the upper right part of the board. This disconnects the ST-Link programmer from the microcontroller part of the port and enables direct access through the pin-header CN3, also labeled SWD.

The Yunjia NRF51822 module supports the Serial Wire Debug (SWD) interface. To access the device the following four lines need to be connected with the STM32x-discovery board:

                 Yunjia module    STM32Fx-discovery
common ground:       GND <-----------> GND
supply voltage:      VDD <-----------> 3V
SWD clock:           SWD <-----------> SWCLK (CN3, pin2)
SWD data I/O:      SWDIO <-----------> SWDIO (CN3, pin4)

The following image shows the wiring for an STM32F0-discovery board (although not the most beautiful…):

Connecting the Yunjia module to an STM32F0-discoveryboard

Programming the Device

RIOT’s provided functionality for debugging and flashing the Yunjia NRF51822 is based on the Open On-Chip Debugger tool. A guide with installation instructions and some other information can be found here.

You can flash the board by calling the following command:

BOARD=yunjia-nrf51822 make flash

and voila, the new firmware should be flashed onto your device.

Resetting the Device

As the Yunjia module does not provide a reset button, RIOT includes a target to reset the board. To do that, just type

BOARD=yunjia-nrf51822 make reset

and your board will reboot.

Debugging the Device

The debugging setup comprises of two parts: a GDB server and a GDB client. To usual workflow is to start the GDB server first and then connect to it with some kind of front-end (e.g. command line, IDE, …).

To start the GDB server, just type

BOARD=yunjia-nrf51822 make debug-server

This will start a local GDB server on port 3333.

If you are fine with working with the GDB command line client, you can start debugging your device by just typing

BOARD=yunjia-nrf51822 make debug

in a second terminal window. This will automatically connect to your previously opened GDB server and will also load your corresponding .elf file.

Alternatively you can configure your IDE (e.g. eclipse or similar) to connect directly to the GDB server. See here for more information on how to configureEclipse

Using UART

The default values are PIN 1: UART_RX and Pin 2: UART_TX (also compare schematic above).

The BLE400 development board contains a CP2102 accessible through /dev/tty.SLAB_USBtoUART. You have to edit periph_conf.h to use it with UART_RX pin 11 and UART_TX pin 9.

The default Baud rate is 115200.

Troubleshooting

Protected at factory (error writing to flash at address 0x000… )

This step may be executed before the first programming of the board. OpenOCD provides the “nrf51 mass_erase” command to remove the protected flag on the bootloader region. RIOT does not use the proprietary Nordic “soft-device”. This is how to run the mass erase:

Open two terminal windows.
In one window, go to the RIOT root folder and run the regarding OpenOCD configuration script with: openocd -f boards/yunjia-nrf51822/dist/openocd.cfg.
In the second terminal, connect to the device via telnet: telnet 127.0.0.1 4444.
If you are successfully connected via telnet, first type halt and then nrf51 mass_erase.

This should have erased the whole memory of the device.