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Communications Introduction

By: David Gitz, EE, Electrical/Programming Team Mentor FRC #1208. Communications Introduction. Audience:. Programming Team Members Electrical Team Members. Topics:. Analog Digital PWM SPI and I2C Serial Network. Analog [1]. Continuous signal

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Communications Introduction

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  1. By: David Gitz, EE, Electrical/Programming Team Mentor FRC #1208 Communications Introduction

  2. Audience: • Programming Team Members • Electrical Team Members

  3. Topics: • Analog • Digital • PWM • SPI and I2C • Serial • Network

  4. Analog [1] • Continuous signal • Real world – Anything wireless is Analog! • FRC: 0 – 5 Volts • Analog Signals connect to Analog Breakout • Have to convert to Digital • Always error: Sampling, Quantization, etc. • Example: • Battery Voltage • Gyroscope/Analog

  5. Digital [2] • Discrete Signal • FRC: 0 or 5 Volts • Much less error • Digital Signals connect to Digital Side Car • Many types of Digital Signals • Example: • Micro-Controllers • Controlling Speed Controllers or Relays

  6. Pulse Width Modulation [3] [4]

  7. Pulse Width Modulation [5] • 2 Standards for different uses: • 1. Averages voltage at load for speed control • 2. Communications. FRC uses this. • Frequency: 50 Hz • Pulse Width: • 1 milliseconds: -100% • 1.5 milliseconds : 0% • 2 milliseconds: 100%

  8. Pulse Width Modulation [6]

  9. SPI and I2C [7] [8] • SPI: Serial Peripheral Interface • Star Topology – 1 Master, many slaves • I2C: Inter-Integrated Circuit • Bus Topology – Any device can be Master • Often used for communicating to different sensors. • Many analog sensors have micro-controllers integrated that use one (or both) of these protocols. • FRC supports I2C through Digital SideCar

  10. Serial • RS-232 anyone… • Most common example in FRC is…CAN! • Which we won’t be going over…Yet.

  11. Network [9] • Computer cables • The little green and orange lights? It means it’s working! • 2 Cables: • Straight-Thru • Almost always use these • Crossover • Connecting Driver Station directly to cRIO • Camera to cRIO • Always try to use ORANGE Crossover’s…

  12. Network [9]

  13. References • http://en.wikipedia.org/wiki/Analog_signal • http://en.wikipedia.org/wiki/Digital_signal • http://en.wikipedia.org/wiki/Pulse-width_modulation • http://pcbheaven.com/wikipages/PWM_Modulation/ • http://www.servocity.com/html/how_do_servos_work_.html • http://www.robotmarketplace.com/products/0-CSMM6.html • http://en.wikipedia.org/wiki/I%C2%B2C • http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus • http://en.wikipedia.org/wiki/Ethernet_crossover_cable

  14. Questions?

  15. Homework • 1. What are the 3 pins on a PWM Cable used for? • 2. When would you use a Crossover Ethernet Cable on a FRC Robot? • 3. Draw an example of: • Analog Signal • Digital Signal • PWM Signal • Reference: References listed in this presentation

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