reel board

Overview

reel board [3] [1] is a evaluation board based on the Nordic Semiconductor nRF52840 SoC. The board was developed by PHYTEC Messtechnik GmbH in cooperation with Zephyr Project for the Hackathon - “Get Connected”. The board has a built-in debug adapter based on the DAPLink interface firmware and NXP MK20DX128VFM5 SoC.

It is equipped with the Electrophoretic (electronic ink) Display (EPD), environmental (temperature, humidity, light, accelerometer) sensors, and Bluetooth connectivity making it easy to experiment and evaluate the Zephyr OS in these kinds of use cases:

• battery powered sensor node

• low-power, low-cost human-machine interface (HMI) for remote control and environmental sensor monitoring

• temperature and humidity monitor on your table

• product, name or price tag

• interactive badge for meetings and conferences

The board provides support for the Nordic Semiconductor nRF52840 ARM® Cortex®-M4F SoC with an integrated 2.4 GHz transceiver supporting Bluetooth® Low Energy and IEEE® 802.15.4.

The schematic can be found on the reel board website [3] [1].

Hardware

On the front of the board are RGB-LED, ADPS9960 and HDC1010 sensors, and Electrophoretic Display. The RGB-LED is controlled by the nRF52840 via GPIO pins. Display is controlled by the nRF52840 via SPI and 3 GPIOs.

On the back side of the board are all other components such as nRF52840, a circuit for the Debug Adapter, On/Off and power source switch, battery holder, buttons and the MMA8652FC (accelerometer) sensor.

ADPS9960 is a Digital Proximity, Ambient Light, RGB and Gesture sensor. HDC1010 is a digital humidity and temperature sensor. MMA8652FC is a 12-bit Digital Accelerometer. All sensors are connected to the I2C bus and one GPIO pin each, which can be used as an interrupt source.

reel board front (Credit: PHYTEC)

reel board back (Credit: PHYTEC)

Since PCB version 1507.2, the nRF52840 SoC is not soldered directly to the board but integrated as a module on a NOTM.2 adapter. The wiring is identical for versions 1507.1 and 1507.2.

Display

GDEH0213B1 is the display with which the board was introduced in 2018. Unfortunately, this display has been discontinued. Currently the board is delivered with the display GDEH0213B72. It is expected that the display will be replaced over time due the short product lifecycle of this type of displays. The following table lists the displays used on the reel board. The label on the ribbon cable can help to distinguish the displays. According to the display type, the correct designation must be used for building an application.

Display	Ribbon Cable Label	Controller / Driver	Board Designation
Good Display GDEH0213B1	HINK-E0213	SSD1673 / ssd16xx	reel_board
Good Display GDEH0213B72	HINK-E0213A22	SSD1675A / ssd16xx	reel_board@2

Power supply

The board is optimized for low power applications and supports two power source configurations, battery and micro USB connector.

The On/Off switch can choose which power source is used.

reel board uses a TPS610981 boost converter to generate supply voltage for nRF52840 and peripherals (sensors and EPD). The boost converter has two modes:

• Active mode - supply voltages for nRF52840 and peripherals are on

• Low Power mode - only supply voltage for nRF52840 is on

The mode is controlled by MODE pin (P1.00).

Note

Actually there is no possibility to reduce energy consumption by the Low Power mode. Both voltages are always on, see: boards/phytec/reel_board/board.c

Supported Features

The reel_board board configuration supports the following hardware features:

Interface	Controller	Driver/Component
NVIC	on-chip	nested vectored interrupt controller
RTC	on-chip	system clock
UART	on-chip	serial port
I2C	on-chip	i2c
PWM	on-chip	pwm
SPI	on-chip	spi
GPIO	on-chip	gpio
FLASH	on-chip	flash
RADIO	on-chip	Bluetooth
SENSOR	off-chip	MMA8652FC polling: ADPS9960 polling: HDC1010 polling

Other hardware features have not been enabled yet for this board.

Connections and IOs

Port P0

Name	Function	Usage
P0.00	XL1	32.768 kHz oscillator
P0.01	XL2	32.768 kHz oscillator
P0.02	expansion connector pin 30	None
P0.03	expansion connector pin 31	None
P0.04	expansion connector pin 19	None
P0.05	expansion connector pin 11	None
P0.06	UART0_TX	UART Console over USB
P0.07	Button	user button (S5)
P0.08	UART0_RX	UART Console over USB
P0.09	expansion connector pin 27	None
P0.10	expansion connector pin 29	None
P0.11	RGB LED (red)	GPIO
P0.12	RGB LED (green)	GPIO
P0.13	PWM LED | Buzzer	GPIO
P0.14	EPD Busy output	GPIO
P0.15	EPD Reset input	GPIO
P0.16	EPD DC input	GPIO
P0.17	EPD SPI3_CS	SPI
P0.18	CPU Reset	Reset (S4)
P0.19	EPD SPI3_CLK	SPI
P0.20	EPD SPI3_MOSI	SPI
P0.21	SPI3_MISO	SPI (not connected)
P0.22	HDC1010 DRDYn	GPIO
P0.23	APDS9960 INT	GPIO
P0.24	MMA8652FC INT1	GPIO
P0.25	MMA8652FC INT2	GPIO
P0.26	I2C_0	I2C
P0.27	I2C_0	I2C
P0.28	expansion connector pin 3	None
P0.29	expansion connector pin 52	None
P0.30	expansion connector pin 1	None
P0.31	expansion connector pin 37	None

Port P1

Name	Function	Usage
P1.00	peripheral power on	GPIO
P1.01	expansion connector pin 32	None
P1.02	expansion connector pin 34	None
P1.03	expansion connector pin 17	None
P1.04	expansion connector pin 15	None
P1.05	expansion connector pin 13	None
P1.06	expansion connector pin 33	None
P1.07	expansion connector pin 35	None
P1.08	expansion connector pin 45	None
P1.09	RGB LED (blue)	GPIO
P1.10	expansion connector pin 47	None
P1.11	expansion connector pin 49	None
P1.12	expansion connector pin 51	None
P1.13	expansion connector pin 36	None
P1.14	expansion connector pin 48	None
P1.15	expansion connector pin 50	None

Solder Jumper and Testpoints

There are several labeled solder jumpers on the board. These can be used to connect a logic analyzer to check the behavior of a driver or to measure the voltage of a signal.

reel board testpoints (Credit: PHYTEC)

I2C bus and sensors testpoints

Name	Type	Usage
J19	closed solder jumper	testpoint I2C SDA
J20	closed solder jumper	testpoint I2C SCL
J7	closed solder jumper	testpoint INT1 MMA8652FC
J24	closed solder jumper	testpoint INT2 MMA8652FC
J11	closed solder jumper	testpoint INT APDS9960
J12	closed solder jumper	testpoint DRDYn HDC1010

EPD testpoints

Name	Type	Usage
J13	closed solder jumper	testpoint EPD Busy
J14	closed solder jumper	testpoint EPD Reset
J15	closed solder jumper	testpoint EPD DC
J16	closed solder jumper	testpoint EPD SPI_CS
J17	closed solder jumper	testpoint EPD SPI_CLK
J18	closed solder jumper	testpoint EPD SPI_MOSI

Power supply testpoint

Name	Type	Usage
J21	closed solder jumper	testpoint peripheral voltage on/off
TP11	testpoint	testpoint peripheral voltage
TP12	testpoint	testpoint nRF52840 supply voltage VDD_nRF
TP13	testpoint	testpoint boost converter input voltage

Built-in Debug Adapter

The debug adapter is based on the DAPLink interface firmware and NXP MK20DX128VFM5 SoC. The adapter is powered via a micro USB connector and is always on when the board is connected to the USB host. reel board can be flashed and debugged, powered either from battery or USB. If the Adapter is powered via USB, the Adapter circuit heats the board slightly and the temperature sensor can output values up to 1.5 degrees higher.

reel board Debug Adapter overview (Credit: PHYTEC)

Debug Adapter Firmware

DAPLink firmware for the adapter can be found at DAPLink reel board Firmware [4] [2]. To update the firmware (if necessary), the adapter must be started in bootloader mode. For this, the board should be disconnected from the USB host, the J22 should be closed (use tweezers for this) and the board reconnected to the USB host.

Debug Adapter Jumper

Name	Type	Usage
J3	open solder jumper	close to pass UART TX to external adapter
J4	open solder jumper	close to pass UART RX to external adapter
J22	open solder jumper	close to start adapter in bootloader mode

Adapter LEDs

Name	Type	Usage
D11	green	flashes when adapter is active
D14	red	reserved
D15	yellow	reserved

Expansion Connector

The expansion connector has the same dimensions and similar pinout as the BBC MicroBit edge connector. The expansion components that are designed especially for the reel board are called link boards.

reel board Expansion Connector (Credit: PHYTEC)

link board BASE

link board BASE is a passive expansion board and allows other link boards or third party shields in Arduino UNO R3 format to be connected to the reel board. In addition, it includes a NOTM.2 connector and more powerful DCDC converter then reel board.

reel board and link board BASE (Credit: PHYTEC)

link board BASE can be used in combination with other link boards or third party shields in two ways:

As an adapter

reel board is plugged into the link board BASE. Both peripherals on reel board and shields can be used as long as there is no conflict between I2C devices. Care should be taken to provide enough power to the complete circuit.

Stand-alone

NOTM.2 adapter is removed from the reel board and connected to NOTM.2 connector on the link board BASE. The wiring to the shield connector is identical to the configuration above and no software modifications for the shield are necessary. Stand-alone configuration is more suitable for applications where peripherals on the reel board are not used or in conflict, power provided by the reel board is not enough, or for prototypes in the field.

link board BASE (Credit: PHYTEC)

Components on the link board BASE:

reel board Connector:

2x40 position edge connector.

Micro USB Connector:

USB can be used as power source. USB data lines are wired to NOTM.2 connector.

NOTM.2 Connector:

Connector for NOTM.2 adapter. If the connector is used then reel board should be removed from reel board connector.

SWD Connector X11:

Wired to NOTM.2 connector. A debug probe can be connected to program or debug MCU in Stand-alone configuration.

Alternative Power Source X5 or X9:

Positive pin is closer to the + character. Nominal voltage is 3.3V, there is no protection against reverse polarity or overvoltage. Use it with care.

Shield Connector:

Connector for link boards and third party shields in Arduino UNO R3 format. Only shields designed for 3.3V supply voltage are supported.

Meaning of the Power Source Switch positions:

EXT

link board BASE is powered from Alternative Power Source Connector X9 or X5.

USB

link board BASE is powered from USB connector (via DCDC converter).

RB

link board BASE is powered from reel board. The available power is below 0.3W and depends on which source is used to power the reel board.

Programming and Debugging

Applications for the reel_board board configuration can be built and flashed in the usual way (see Building an Application and Run an Application for more details).

Flashing

If you use Linux, create a udev rule (as root) to fix a permission issue when not using root for flashing.

# echo 'ATTR{idProduct}=="0204", ATTR{idVendor}=="0d28", MODE="0666", GROUP="plugdev"' > /etc/udev/rules.d/50-cmsis-dap.rules

Reload the rules and replug the device.

$ sudo udevadm control --reload-rules

Finally, unplug and plug the board again for the rules to take effect.

Build and flash applications as usual (see Building an Application and Run an Application for more details).

Here is an example for the Hello World application.

First, run your favorite terminal program to listen for output.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the port where the reel board can be found. For example, under Linux, /dev/ttyACM0.

Then build and flash the application in the usual way.

# From the root of the zephyr repository
west build -b reel_board samples/hello_world
west flash

Note

Please use reel_board@2 to build a application for the board equipped with the GDEH0213B72, see Display.

# From the root of the zephyr repository
west build -b reel_board@2 samples/hello_world
west flash

Debugging

You can debug an application in the usual way. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b reel_board samples/hello_world
west debug

Testing the LEDs and buttons

There are 2 samples that allow you to test that the buttons (switches) and LEDs on the board are working properly with Zephyr:

• Blinky

• Button

You can build and flash the examples to make sure Zephyr is running correctly on your board.

References

[1] (1,2)

https://www.phytec.de/reelboard/

[2]

https://github.com/PHYTEC-Messtechnik-GmbH/DAPLink/tree/reel-board

[3] (1,2)

https://www.phytec.de/reelboard/

[4]

https://github.com/PHYTEC-Messtechnik-GmbH/DAPLink/tree/reel-board