This is the documentation for the latest (master) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

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.

Hexiwear

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:

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

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

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.

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:

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.