Page 12 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

Contents xi

Direct-Sequence Spread Spectrum .............................. 133
Automatic Selection of Dual Transmit Channels ............ 135
Switching Channels for Every
Data Frame Transmitted .............................. 135
Transmission of SOP and PN Packets . . . . . . . . . . . . . . . . . . . . . 135
Transmission of Two Sets of Cyclic
Redundancy Checks ................................. 135
Transmission of the GUID ............................... 136
Frequency-Hopping Spread Spectrum .......................... 136
Binding or Pairing ..................................... 137
Experimental R/C System Demonstration ...................... 139
Measuring R/C Channel Pulse Width and
Rate with the BOE ......................................... 145
BOE Pulse-Width Measurements ......................... 146
BOE Pulse-Rate Measurements .......................... 150
Telemetry ................................................... 155
Summary ................................................... 159

7 Servo Motors and Extending the Servo Control System . . . . . . . . . . 161
Introduction ................................................. 161
Exploring a Standard R/C Analog Servo Motor .................. 161
The Digital Servo ............................................ 166
Continuous Rotation Servos ................................... 168
R/C Signal Display System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
Elev-8 LED-Lighting Controller ................................ 179
Tilting Mechanism for a First-Person Viewer ..................... 188
Summary ................................................... 192

8 GPS and a Real-Time Situational Display . . . . . . . . . . . . . . . . . . . . . . 193
Introduction ................................................. 193
GPS Basics .................................................. 193
Brief GPS history ...................................... 193
How GPS Functions .................................... 194
Quadcopter GPS Receiver ..................................... 198
GPS Receiver UART Communications .................... 199
Initial GPS Receiver Test ................................ 200
NMEA Protocol .............................................. 202
Latitude and Longitude Formats ......................... 203
Parsed GPS Message ................................... 204
Propeller Mini ............................................... 204
Radio-Frequency Transceiver Module .......................... 205
XBee Hardware .............................................. 207
XBee Data Protocol ........................................... 209
XBee Functional Test ......................................... 212
XBee Range Check ..................................... 216