Team 1 Technical Lecture

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Team 1 Technical Lecture

• Serial Communication
• Manager Jerome Yancy
• Documentation Kenneth Booker
• Coordinator Paul Suchyta
• Webmaster Khalid Saufee
• Presentation Kevin Fells

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Introduction

• Serial Communication
• Transfers 1-bit at a time
• Typically used in component-to-component
• Parallel Communication
• Bits sent over many wires simultaneously
• Faster than a serial communication
• Multiple wires needed

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Introduction (cont.)

• Advantages Of Serial Communications
• Clocked faster
• Many ICs have serial interface
• Fewer wires
• Cheap
• Common Application
• Dial-up modems
• Printers
• Microcontroller programmers (PIC)

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Synchronous Asynchronous

• Synchronization
• Electronic devices rhythm
• Synchronous Transmission
• Transmit data along regular structured intervals
  
• Asynchronous Transmission
• Event driven
• Irregular sending data by specific identifiers
• Advantages
• Simple
• Inexpensive
• Set-up very fast
• Disadvantages
• Large relative overhead
• Timing errors can occur

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Bidirectional Communication

• All serial ports allow for duplex, or two-way,
  communication between devices
• Half-duplex
• Communication can only occur in one direction at
  a given time
• Collision avoidance necessary
• Full-duplex
• Communication can occur in both directions
  simultaneously
• Each device has separate input and output pins
• Requires more wires
• Higher throughput
• Collisions less problematic

Half-Duplex
Full-Duplex
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Single-Ended vs. Differential Signaling

• Single-Ended
• Uses one wire
• Receiver evaluates signal as voltage of wire
  relative to reference
• More common approach
• Differential
• Uses two wires
• Receiver evaluates signal as difference of wire
  voltages
• Improved noise immunity
• Tolerance of device ground variation
• Greater resistance to electromagnetic interference

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Physical Signal Characteristics

• Binary representation of data by line voltage
• Idle State
• Open-collector orientation common
• Data sent in frames
• Start bits (asynchronous only)
• Data
• Parity (optional)
• Stop bits (asynchronous only)
• Padding (synchronous only)

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Flow Control

• Sender/Receiver issue
• Manages data transmission
• Handshaking
• Special characters
• (XON/XOFF)
• Implementing proper flow control
• Use preprogrammed routines from a reliable source

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Serial Peripheral Interface

• Operates in full duplex mode
• Synchronous
• Communicates in master/slave mode
• Four logic signal
• Operation and Data Transmission
• Only one master
• Can have multiple slave
• Shift register

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Serial Peripheral Interface Bus

• Advantages
• Full duplex communication
• Higher throughput than other formats
• Simple hardware interfacing
• Disadvantages
• Requires more pins on IC packages than other
  formats
• Only one master
• No slave acknowledgement
• Applications
• Sensors, memory, communications

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I²C

• Inter-Integrated Circuit
• Developed by Philips in the early 1980s
• Simplicity and low manufacturing cost
• SDA and SCL

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How I²C Works

• Multi-Master Support

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Why use I²C

• Cost-effective for low to medium speed
  chip-to-chip communication
• 100 kbit/sec to 3.4 Mbit/sec
• Bus error detection and recovery
• Can easily be added to most microcontrollers

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RS -232 Standard

• Overview
• Supports synchronous and asynchronous
• Full duplex manner
• Supports concurrent data flow in both directions
• Current applications
• Old design of peripherals, industrial equipments,
  and console ports
• Multiple systems
• Isolation between each system and bus

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USB (Universal Serial Bus)

• General Characteristics
• Half-duplex communication
• Differential signaling
• Establishes communications by Handshaking
• Transmits at up to 480Mbits/sec (USB 2.0)
• Used in memory storage devices (flash drives)
• Becoming a standard for computer/device
  connections

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Advantages and Disadvantages

• Advantages
• Plug-and-play technology
• Can power devices (up to 500 mA for USB 2.0)
• One host can control up to 127 devices

• Disadvantages
• Cable length set at a max of five meters
• Slower than PCI formats (such as firewire)

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UART (Universal Asynchronous Receiver/Transmitter)

• Integrated Circuit component of a serial
  communication system
• Converts data between serial and parallel forms
• Used with a variety of serial standards
• Typically perform full-duplex communication
• USART variant allows synchronous or asynchronous
  communication
• Commonly included in general-purpose
  microcontrollers

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UART Components

• Clock Generator
• Multiple of bit transmission rate
• Sampling used to filter out noise spikes
• Shift Registers
• Input shift register performs parallel-to-serial
• Output shift register performs serial-to-parallel
• Transmit/Receive control logic
• Buffers
• Ensures that data will not be lost if end device
  operates at a different speed than data is
  transmitted over the line

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Sample UART IC Block Diagram
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Choosing a Communication Format(Things to
Consider)

• Support of format by components
• Physical distance between components
• Error Checking
• Transmission speed
• Ease of implementation
• Cost

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Our Design

• Communication between the PIC processor and Xbee
  Module
• Supported by both components
• PIC communicates data to Xbee (which is a
  wireless transceiver)
• UART characteristics
• Full-duplex communication
• Buffer characteristic minimizes data loss
• Transmission speed is adequate
• Communication standard in general purpose
  microcontrollers

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Summary

• Serial communication characteristics
• Serial communication formats
• SPI
• I²C
• RS-232
• USB
• UART
• Choosing the right communication standard

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Questions?