Navigator Hardware Setup

Guides in This Series

Introduction

The Navigator is an add on board for the Raspberry Pi 4 that enables autonomous vehicles running ArduPilot and BlueOS. The board is equipped with a suite of sensors to enable autonomous vehicle control with the Raspberry Pi 4 including digital accelerometer, gyroscope, dual magnetometers, ADC and pressure sensor. It also includes a rich set of connectors for connecting all of your vehicle’s hardware like servos, motor controllers, sonar, GPS and other sensor peripherals.

The Navigator is used on the BlueROV2 and BlueBoat in conjunction with BlueOS software, but it can also be used for a wide range of robotics applications such as ROVs, USVs, drones, ground vehicles, and just about anything that moves!

This guide will go over assembling the Navigator kit and the hardware setup. Along with the information in this guide, be sure to visit the ArduPilot documentation for in depth information for the type of vehicle you are building.

• ArduSub
• ArduCopter
• ArduPlane
• ArduRover

In the Box

The Navigator kit comes with the following components in the box:

• 1 x Navigator PCB
• 1 x Navigator heatsink
• 1 x Raspberry Pi mounting standoff
• 1 x 128GB microSD card with BlueOS
• 3 x Thermal pads
• 2 x 3-pin JST GH cable for accessories/expansion
• 1 x 4-pin JST GH cable for accessories/expansion
• 3 x 6-pin JST GH cable for accessories/expansion
• 2 x SOS leak probe, 12″ length
• 4 x M2.5×8 button head cap screw
• 2 x #3-28×3/8 mounting screw

The Raspberry Pi 4 is not included in the kit but can be purchased together.

Hardware Overview

Navigator PCB Schematic (PDF)

All sensor and IC datasheets are available in the Navigator technical details.

Compatibility

The Navigator is compatible with the following Raspberry Pi models:

• Raspberry Pi 4 Model B

Assembling the Navigator Stack

The Navigator kit includes all the required components and hardware to connect it to a Raspberry Pi. To assemble the Navigator stack, you will need:

• Navigator PCB
• Navigator Heatsink
• Raspberry Pi 4 Model B
• Thermal Pads
• Raspberry Pi Mounting Standoff
• 4 x M2.5×8 Button Head cap screw

You will also need the following tools:

• 1.5 mm hex driver

1. Remove the protective covering from the square thermal pads and apply them to the underside of the Navigator heatsink. The heatsink has squares showing where the thermal pads should be placed.

2. Place the Navigator heatsink on top of the Raspberry Pi. The thermal pads should sit between the Navigator heatsink and the Raspberry Pi.

3. Place the Raspberry Pi mounting standoff on the underside of the Raspberry Pi. Use two M2.5×8 button head screws and the 1.5 hex driver to secure the standoff and Navigator heatsink to the Raspberry Pi. The screws should sit in the recessed standoff mounting holes and screw into the heatsink.

4. Place the Navigator PCB on top of the Raspberry Pi and heatsink and plug it fully onto the Raspberry Pi GPIO pins. Secure the Navigator PCB to the heatsink using the remaining M2.5×8 button head screws.

The Navigator Stack is now ready to mount in your vehicle.

Mounting

The Navigator can be mounted in your vehicle using the included #3-28×3/8 thread forming screws.

The default mounting orientation for the Navigator is with the Navigator PCB facing topside up and the arrow pointing towards the front of the vehicle.

The Navigator stack can also be mounted on the vehicle in a number of different orientations supported by the autopilot software. If you are not using the default orientation, you can specify your mounting orientation during the sensor calibration step in the software setup guide.

Supplying Power

The Navigator has two independent power circuits, the main circuit is powered by the primary and secondary power inputs, and the other is powered by the AUX 5V power input. The diagram below shows which ports are connected to each circuit.

The Navigator has two power inputs that supply power to the Navigator PCB and Raspberry Pi. The voltage supplied to either of these inputs must be 5–5.35V. The power supply used should be capable of delivering at least 4.5 amps. The Navigator + Raspberry Pi will be powered when using either power input.

Main 5V (Primary)

The Main 5V input is the primary power input. This input accepts regular servo-style 3 position 0.1″ pitch female headers. The Blue Robotics 5V6A Power Supply is recommended but any 5V UBEC that can supply at least 4.5A will work.

Pinout:

POWER (Secondary)

Navigator can also be powered using a power module connected to the POWER port. This port is also used to connect analog power modules to measure and provide voltage and current consumption information.

Pinout:

Power Switching

The primary MAIN 5V and secondary POWER inputs may be powered simultaneously. In this case, the Navigator Stack will draw power from the primary MAIN 5V input unless the voltage at the primary input dips below 4.7V. In this event, the Navigator will switch to draw power from the secondary POWER input until the primary input voltage is above 5.1V, then the Navigator will switch back to the primary power input. It is advised to use a power supply capable of delivering at least 4.5 amps to avoid input switching events.

Auxiliary Power Input

The AUX 5V input supplies power to the servo rail, the RGB header, and PWM0 header. To power any servos or other devices connected to these outputs a power supply must be connected to the AUX 5V input. The input voltage connected to the AUX 5V input is delivered to all devices connected to the servo rail, RGB header, and PWM0 header. Ensure that the input voltage range specification of any devices connected to the servo rail, RGB header, or PWM0 header is compatible with the voltage supplied.

Pinout:

Power Indicator LEDs

There are two power status indicator LEDs on the Navigator.

5V LED: Indicates the Navigator board is receiving power.

3.3V LED: Indicates the Navigator board is providing power to the on-board electronics.

Servos and ESCs

Powering the Servo Rail

The primary MAIN 5V and secondary POWER inputs do not supply power to the servo rail so it must be powered separately using the AUX 5V input. Power can also be supplied using a BEC connected to any of the PWM output channels. The input voltage connected to the AUX 5V input or servo rail is delivered to all devices connected to the servo rail, RGB header, and PWM0 header. Ensure that the input voltage range specification of any devices connected to the servo rail, RGB header, or PWM0 header is compatible with the voltage supplied.

Servo Rail/PWM Output

ESCs and servos can be connected to PWM outputs 1–16. The output can also be configured as 3.3V digital outputs to control relays, switches, etc. The maximum current available on each signal pin to drive relays, etc., is 15 mA

Pinout:

JST GH PWM Connectors

PWM output channels 1–8 are also available on JST GH connectors located above the servo rail. These PWM signals are connected to both the JST GH connector and the servo rail, so the same signal will be present on both connectors. The JST GH connectors are intended for higher density wiring in space constrained applications like wiring 4-in-1 ESCs.

Pinout:

RC Radio

An RC radio can be connected to the RC input connector. Both inverted and noninverted RC protocols are supported.

Pinout:

UART/SBUS Jumper

By default the RC input is configured for SBUS (inverted) protocol. To use a radio that uses a normal (noninverted) UART signal, cut the trace between the SBUS and center solder pad and solder the jumper on the back of the Navigator PCB to the UART position. To reconfigure the RC input for SBUS after the trace has been cut, solder the jumper in the SBUS position.

The table below shows common RC serial protocols and the required jumper configuration.

Serial Devices

Serial devices may be connected to the 6-pin serial (SERIAL 1,3,4,5) connectors. Additional serial devices may be connected to the Raspberry Pi 4 USB ports via a USB-UART adapter like the BLUART.

Pinout:

Telemetry Radio

Telemetry radios may be connected to any of the 6-pin serial connectors. The recommended setup is to use SERIAL 1 for a telemetry radio connection.

GPS

A serial GPS module may be connected to any of the 6-pin serial connectors. Some Dronecode compatible GPS modules also include onboard I²C devices like compasses and barometers. These modules should be connected to the SERIAL 5 + I²C 6 connector in order to use the I²C devices on the GPS module.

Pinout:

I²C Devices

I²C sensors should be connected to the I²C 6 ports. The I²C bus is also accessible from the SCL and SDA pins on the SERIAL 5 + I²C connector. The clock and data lines on the I²C connectors are connected in parallel, and connect to the Raspberry Pi 4 SOC I²C 6 unit. External pullup resistors are optional, there are pullup resistors on the Navigator PCB.

Pinout:

Analog Devices

There are two analog-to-digital converter connectors, one with a 0–3.3V signal input, and one with a 0–6.6V signal input. Ensure that the signal voltage applied to these connectors is within the indicated allowable range. If these limits are exceeded, the ADC may be permanently damaged.

Pinout:

Leak Detection

The Navigator has a built-in leak detection circuit for vehicles where water ingress is a possibility. Two leak detection probes can be connected directly to the Navigator using the Leak ports.

Pinout:

If a leak is detected by one of the probes, the LEAK indicator LED will illuminate red and a failsafe warning will be triggered in software.

If additional probes are required, an SOS Leak Sensor can be connected to the AUX Leak header.

Pinout:

Replacement leak probes are available here.

RGB LED Header

The RGB LED header supports connecting an addressable LEDs strips based on WS2812 or SK6812 LEDs, also known as “NeoPixels”. The RGB LED connector is powered by AUX 5V power input.

Pinout:

PWM0/Fan Header

The PWM0 connector is intended for controlling a fan for cooling. Unlike the servo rail PWM 1–16 connectors, which are connected to the PCA9685 PWM driver, the PWM pin on this connector is connected directly to the Raspberry Pi 4 SOC GPIO18 pin, which can function as the Raspberry Pi SOC PWM0 output signal. This pin may also be used as a general purpose input/output or PWM function with user application code.

Pinout:

Camera

BlueOS supports USB cameras with H.264 encoded video streams such as the Blue Robotics Low-Light HD USB Camera. Connect the USB camera to one of the Raspberry Pi USB ports and BlueOS will auto-configure the camera stream the first time it starts up. The camera and video stream configuration can be managed from the BlueOS web interface. Please visit the BlueOS documentation for more information.

Next Steps

To continue with the setup process, proceed to the Navigator Software Setup guide.