1. CYMOTE
MAY 1735
Team: Michael Linthicum, Kyle Fischer, Daniel Shauger, Nicholas Juelsgaard, Samuel Neff
Advisor: Dr. Thomas Daniels
INTRODUCTION
CprE 185 currently utilizes a device called the Arduino Esplora. The Esplora is a handheld controller with a simple set of I/O on board, including some buttons, a joystick, Bluetooth, and, most importantly, a three dimensional accelerometer. The students in CprE 185 collect real-world data from the Esplora to solve interesting programming and physics-based challenges. Unfortunately, the Esplora has been discontinued and the department will need a replacement as the Esplora becomes obsolete.
After an extensive search turning up no comparable replacements, our senior design group decided to design and build a beta model for a new device for CprE 185 specifically designed for this class. This new device, called the CyMote, will provide all the functionality previously provided while costing less. Our beta model has laid the foundation for this device to be improved upon and produced by future students and/or faculty.
I/O COMPONENTS
9° of Freedom – 3D accelerometer
Joystick – (x,y analog inputs, button press)
4 game controller style input buttons
Status LEDs for all the devices
Tricolor LED for display/status/fun
FUNCTIONAL DESIGN REQUIREMENTS
Survive a 30’ drop in a soft container
Robust enough to handle misuse
Communicate with a partner PC over Bluetooth
Low power consumption from onboard rechargeable batteries
Power on/off switch
Eight hours of battery life
Communicates without loss or bugs over USB and BLE
Streams >30 accelerometer records per second
Permanently named (physical, BLE, code) for paring with computers
Bluetooth Low Energy (BLE)
BLE is our main communication method between the board and the PC. It is the bridge between our sensors and the PC. BLE is different from regular Bluetooth. Regular Bluetooth is always on, always listening and always receiving. BLE checks for data tx and rx far less frequently, so BLE is a trade-off between data transfer throughput and battery life. The board uses C (programming language), the Atmel Software Framework (libraries), we developed it in Atmel Studio (developing environment).
BLE was tested by sending static dummy data first. Then moved to sending raw accelerometer data. Once one board could send data correctly we moved to testing throughout, multiple devices, and distance.
NON-FUNCTIONAL DESIGN REQUIREMENTS
Look like a game controller
Stream data in real time – fast enough to register current movement on screen as having no lag
Beta model built on a handheld size PCB
Permanently securable to the PCs in the CprE 185 lab to ensure they don’t “walk away”
Operating Environment
Freshman Labs
Three story drop
Printed Circuit Board Design
Once parts had been selected and the circuit completed, we began the design of our PCB using Multisim. After our first version was completed and we had soldered our components to the boards, we began our testing phase.
Each board was systematically checked by verifying the power section, followed by the charging section, MCU, LSM9DS1, and the buttons/joystick. Necessary changes were noted in a document for the next revision. Using this testing method to improve our design, we designed and produced two additional PCB revisions.
Buttons
Four separate buttons and a single joystick-tied button interact with the MCU through the GPIO pins and digital signaling, meaning that the button signals are read in as only ones and zeroes. These values are packaged with the joystick values and sent through BLE to the PC wrapper as five separate values that can be individually parsed by the user.
LSM9DS1
This is the nine degrees of freedom chip. This chip includes three sensors: gyroscope, accelerometer, and magnetometer. The LSM9DS1 communicates with the ATSAMB11 over a protocol known as Serial Peripheral Interface (SPI).The ATSAMB11 came with an SPI hardware interface and an Atmel API to interact with it. Due to poor documentation of the API and few examples to guide us, we decided to simulate in software (Bit Bang) our own implementation of the SPI interface.
Joystick
The joystick has two axes controlled by two separate potentiometers reading in the X and Y directions. These MCU uses two separate ADC channels to read in these values as a numeric value between 0 and 1023, and from there the data is sent over BLE to the PC wrapper for further interpretation.
PC Wrapper
All the data collected by the sensors are packed into five packets that are sent over BLE from the MCU over to the wrapper running on a standalone PC. Once the data is received, static values inside the wrapper are updated to the most current data. When the wrapper is run, the user can pass in flags corresponding to the specific data they want from the wrapper. For example, if the user runs the wrapper with the ‘a’ and ‘t’ flags, the wrapper will display accelerometer and time values from the Cymote.
The data gathered from the LSM9DS1 is sent in three raw values per sensor to the PC Wrapper where it is processed into meaningful values. Languages, development tools, and development environments used in the implementation and testing of this device include the LSM9DS0 nine degrees of freedom sensor, Arduino Uno, Arduino SPI Library, Arduino IDE, C, Atmel Studio, the LSM9DS1 nine degrees of freedom sensor, Atmel Software Foundation Libraries, and the ATSAMB11 microcontroller.
Acknowledgements: Dr. Thomas Daniels, Dr. Gary Tuttle, Lee Harker