Hampod Project Hardware

Introduction

The hardware of the Hampod is a PCB that is mounted on top of the NanoPi. The board contains 2 USB-A ports, a DB9 port for RS232 communication, an internal speaker amplifier, audio jack for external speakers, a keypad, a fan to cool the power supply, and a 5-volt DC power supply. A 1A fuse is in the power supply circuit if a short occurs to prevent damage to either the NanoPi or the rest of the board. There are two indicator LEDs on the design, one for power and another for determining if the audio jack is in use. The audio indicator LED is for testing and may be omitted. If the user chooses a switching regulator replacement over the standard 7805 linear regulator, the fan does not need to be installed.

Hardware Components

Audio Jack

By default, the internal speaker is used for outputting sound. However, in the scenario when a user wants a louder output through external speakers, the audio jack provides the ability to do so. For debugging purposes, an LED indicates when the audio jack is in use.

Fan

The fan provides air to the power supply since it heats up. If the user chooses a switching regulator replacement over the standard 7805 linear regulator, the fan does not need to be installed.

Internal Speaker

The internal speaker outputs an audible text-to-speech voice for the user when interacting with the Hampod. Since there is an external speaker jack, the interal speaker is used by default when no other audio device is plugged in.

Keypad

The user operates the Hampod with a 4x4 touch tone keypad. This keypad is identical to a keypad of a touch tone phone with the addition of a fourth column containing the A, B, C, and D keys. This is a very simple input peripheral that is ideally easy for a visually impaired user to use.

Output Ports

The Hampod contains three USB 2.0 ports and one RS232 serial port.

USB

One USB port is provided on the PCB of the NanoPi while the other two are brought out in the hardware circuit.

Serial

A level shifter is provided in the Hampod to allow the use of the UART port on the Hampod with legacy radios that only have a serial port with RS232 signal levels.

NanoPi Neo

The NanoPi NEO is a single board computer (SBC) that runs our code. It has a quad-core CPU and 512 MB of memory. The code and files are stored on an SD card which allows us to have much more disk space than a microcontroller. This SBC also comes with USB which allows us to connect to newer radios which contain a USB port. The NanoPi is low cost and has a small form factor which lets us keep the Hampod cheaper and small.

For more information about the NanoPi Neo, the wiki can be found here

For the product link, the website can be found here

Hardware Schematic