Hexiwear

Overview

Hexiwear is powered by a Kinetis K64 microcontroller based on the ARM Cortex-M4 core. Another Kinetis wireless MCU, the KW40Z, provides Bluetooth Low Energy connectivity. Hexiwear also integrates a wide variety of sensors, as well as a user interface consisting of a 1.1” 96px x 96px full color OLED display and six capacitive buttons with haptic feedback.

• Eye-catching Smart Watch form factor with powerful, low power Kinetis K6x MCU and 6 on-board sensors.

• Designed for wearable applications with the onboard rechargeable battery, OLED screen and onboard sensors such as optical heart rate, accelerometer, magnetometer and gyroscope.

• Designed for IoT end node applications with the onboard sensor’s such as temperature, pressure, humidity and ambient light.

• Flexibility to let you add the sensors of your choice nearly 200 additional sensors through click boards.

Hardware

• Main MCU: NXP Kinetis K64x (ARM Cortex-M4, 120 MHz, 1M Flash, 256K SRAM)

• Wireless MCU: NXP Kinetis KW4x (ARM Cortex-M0+, Bluetooth Low Energy & 802.15.4 radio)

• 6-axis combo Accelerometer and Magnetometer NXP FXOS8700

• 3-Axis Gyroscope: NXP FXAS21002

• Absolute Pressure sensor NXP MPL3115

• Li-Ion/Li-Po Battery Charger NXP MC34671

• Optical heart rate sensor Maxim MAX30101

• Ambient Light sensor, Humidity and Temperature sensor

• 1.1” full color OLED display

• Haptic feedback engine

• 190 mAh 2C Li-Po battery

• Capacitive touch interface

• RGB LED

For more information about the K64F SoC and Hexiwear board:

• K64F Website

• K64F Datasheet

• K64F Reference Manual

• Hexiwear Website

• Hexiwear Fact Sheet

• Hexiwear Schematics

Supported Features

The hexiwear_k64 board configuration supports the following hardware features:

Interface	Controller	Driver/Component
NVIC	on-chip	nested vector interrupt controller
SYSTICK	on-chip	systick
PINMUX	on-chip	pinmux
GPIO	on-chip	gpio
I2C	on-chip	i2c
WATCHDOG	on-chip	watchdog
ADC	on-chip	adc
PWM	on-chip	pwm
UART	on-chip	serial port-polling; serial port-interrupt
FLASH	on-chip	soc flash
SENSOR	off-chip	fxos8700 polling; fxos8700 trigger; fxas21002 polling; fxas21002 trigger; max30101 polling
RNGA	on-chip	entropy; random

The default configuration can be found in the defconfig file:

boards/arm/hexiwear_k64/hexiwear_k64_defconfig

Other hardware features are not currently supported by the port.

Connections and IOs

The K64F SoC has five pairs of pinmux/gpio controllers.

Name	Function	Usage
PTA29	GPIO	LDO_EN
PTB0	I2C0_SCL	I2C / MAX30101
PTB1	I2C0_SDA	I2C / MAX30101
PTB12	GPIO	3V3B EN
PTB16	UART0_RX	UART Console
PTB17	UART0_TX	UART Console
PTC8	GPIO / PWM	Red LED
PTC9	GPIO / PWM	Green LED
PTC10	I2C1_SCL	I2C / FXOS8700 / FXAS21002
PTC11	I2C1_SDA	I2C / FXOS8700 / FXAS21002
PTC14	GPIO	Battery sense enable
PTC18	GPIO	FXAS21002 INT2
PTD0	GPIO / PWM	Blue LED
PTD13	GPIO	FXOS8700 INT2
PTE24	UART4_RX	UART BT HCI
PTE25	UART4_TX	UART BT HCI

Note

To enable battery sensing, you will need to enable the en_bat_sens regulator in Devicetree. Similarly, to enable devices connected to the 1V8 or 3V3 power rails (sensors), you will need to enable the en_ldo and en_3v3b regulators in Devicetree.

System Clock

The K64F SoC is configured to use the 12 MHz external oscillator on the board with the on-chip PLL to generate a 120 MHz system clock.

Serial Port

The K64F SoC has six UARTs. One is configured for the console, another for BT HCI, and the remaining are not used.

Programming and Debugging

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

Configuring a Debug Probe

A debug probe is used for both flashing and debugging the board. This board is configured by default to use the OpenSDA DAPLink Onboard Debug Probe, but because Segger RTT is required for a console on KW40Z, we recommend that you reconfigure the board for the OpenSDA J-Link Onboard Debug Probe.

Note

OpenSDA is shared between the K64 and the KW40Z via switches, therefore only one SoC can be flashed, debugged, or have an open console at a time.

Option 1: OpenSDA J-Link Onboard Debug Probe (Recommended)

Install the J-Link Debug Host Tools and make sure they are in your search path.

Follow the instructions in OpenSDA J-Link Onboard Debug Probe to program the OpenSDA J-Link Generic Firmware for V2.1 Bootloader. Check that switches SW1 and SW2 are on, and SW3 and SW4 are off to ensure K64F SWD signals are connected to the OpenSDA microcontroller.

Option 2: OpenSDA DAPLink Onboard Debug Probe

Install the pyOCD Debug Host Tools and make sure they are in your search path.

Follow the instructions in OpenSDA DAPLink Onboard Debug Probe to program the OpenSDA DAPLink Hexiwear Firmware. Check that switches SW1 and SW2 are on, and SW3 and SW4 are off to ensure K64F SWD signals are connected to the OpenSDA microcontroller.

Add the arguments -DBOARD_FLASH_RUNNER=pyocd and -DBOARD_DEBUG_RUNNER=pyocd when you invoke west build to override the default runner from J-Link to pyOCD:

# From the root of the zephyr repository
west build -b hexiwear_k64 samples/hello_world -- -DBOARD_FLASH_RUNNER=pyocd -DBOARD_DEBUG_RUNNER=pyocd

Configuring a Console

Regardless of your choice in debug probe, we will use the OpenSDA microcontroller as a usb-to-serial adapter for the serial console.

Connect a USB cable from your PC to CN1.

Use the following settings with your serial terminal of choice (minicom, putty, etc.):

• Speed: 115200

• Data: 8 bits

• Parity: None

• Stop bits: 1

Flashing

Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b hexiwear_k64 samples/hello_world
west flash

Open a serial terminal, reset the board (press the T4 button), and you should see the following message in the terminal:

***** Booting Zephyr OS v1.14.0-rc1 *****
Hello World! hexiwear_k64

Debugging

Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b hexiwear_k64 samples/hello_world
west debug

Open a serial terminal, step through the application in your debugger, and you should see the following message in the terminal:

***** Booting Zephyr OS v1.14.0-rc1 *****
Hello World! hexiwear_k64

Using Bluetooth

Configure the KW40Z as a Bluetooth controller

The K64 can support Zephyr Bluetooth host applications when you configure the KW40Z as a Bluetooth controller.

1. Download and install the KW40Z Connectivity Software. This package contains Bluetooth controller application for the KW40Z.

2. Flash the file tools/binaries/BLE_HCI_Modem.bin to the KW40Z.

Now you can build and run the sample Zephyr Bluetooth host applications on the K64. You do not need to repeat this step each time you flash a new Bluetooth host application to the K64.

Peripheral Heart Rate Sensor

Navigate to the Zephyr samples/bluetooth/peripheral_hr sample application, then build and flash it to the Hexiwear K64. Make sure the OpenSDA switches on the docking station are configured for the K64.

# From the root of the zephyr repository
west build -b hexiwear_k64 samples/bluetooth/peripheral_hr
west flash

Reset the KW40Z and the K64 using the push buttons on the docking station.

Install the Kinetis BLE Toolbox on your smartphone:

• Kinetis BLE Toolbox for iOS

• Kinetis BLE Toolbox for Android

Open the app, tap the Heart Rate feature, and you should see a Zephyr Heartrate Sensor device. Tap the Zephyr Heartrate Sensor device and you will then see a plot of the heart rate data that updates once per second.