Bluebird Hardware Overview

The Bluebird hardware is built around the nRF52840 chipset. The nRF52840 combines network and application processing into a single chipset and includes support for a variety of on-chip peripherals. Bluebird leverages the nRF52840’s integrated USB 2.0 controller for both drag-and-drop programming and debugging without requiring any additional hardware. Bluebird includes a 6-axis accelerometer, light/color sensor, piezo speaker, Neopixel LED, and temperature sensor.
Two key pieces of information to help understand the internals of the Bluebird is schematic, which shows the detailed component data and connectivity of the device.

Hardware Description

nRF52 Application Processor The nRF52 application processor is where user programs run. A single, complete application including user code, runtime code and Bluetooth stack is loaded and run directly from on chip flash memory. All user accessible GPIO pins are provided by this processor. There is an onboard 2.4GHz radio engine used to provide Bluetooth capabilities via an off-chip aerial.

Bluetooth Wireless Communication

The on board 2.4GHz transceiver supports Bluetooth communications via the Nordic S140 SoftDevice, which provides a fully qualified Bluetooth low energy stack. This allows the Bluebird to communicate with a wide range of Bluetooth devices, including smartphones and tablets.

Reset Button

The button on the front of the Bluebird, is tactile momentary push to reset purpose. A pullup resistor ensures a logical ‘1’ when the button is released, and a logical ‘0’ when the button is pressed.

Display

The display is a smart LED control circuit and light emitting circuit in one controlled LED source. It is connected to the Bluebird through a unipolar NRZ communication mode.

Motion sensor

The 1.7 Bluebird variant has a combined accelerometer and gyroscope chip that provides 6-axis MotionTracking. This device is connected to the application processor via the I2C bus.

Temperature Sensing

The ICM-20600 has an integrated temperature sensor. It provides an estimate of the ambient temperature

Light/Color Sensing

The Bluebird integrates an analog ambient light sensor. This sensor is placed next to Neopixel LED in order to allow color sensor measurements via software using the measurement for a specific color emitted by the Neopixel LED and measured by the ALS.

Speaker

The Bluebird integrates a speaker controlled by PWM.

General Purpose Input/Output Pins

The central breakout connector brings out many of the GPIO circuits of the application processor. None of these circuits are shared with other functions of the Bluebird. Note: the nRF52840 datasheet states that GPIO pins may be in std-drive (15mA) and high-drive (5mA) mode, with a maximum of 3 pins in high-drive mode at any one time.

Power Supply

Power to the Bluebird may be provided via the USB connection, or via a battery plugged into the top connector. Note: The + pads on the side CANNOT be used to supply the Bluebird, these are Vout pads for external sensors.

USB Communication

The Bluebird has an on board USB communications stack, that is built into the firmware of the NRF52840 chip. This stack provides the ability to drag and drop UF2 files onto the NRF52BOOT drive in order to load code into the application processor. It also allows serial data to be streamed to and from the Bluebird application processor over USB to an external host computer

Debugging

The JTAG interface allows debugging through the connector J1. In order to access to this connection you need to use TagConnect connector

Mechanical

You can find 2D and 3D CAD drawings and models of the Bluebird including all the important dimensions. These models can be used as a basis for generating marketing and project images of the Bluebird, but also as a basis for accurate manufacture of attachments e.g. via 3D printing.