Programming Hardware Devices

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  • 1. Software Developers View of Hardware Programming Hardware Devices
  • 2. What does this mean?
    • Computers usually interact with outside sources for input and output:
      • CD-ROM
      • Mouse
      • Keyboard
      • Scanner
      • Monitor.
  • 3. What does this mean?
    • Most software developers require their software to interact with these devices.
    • So it is therefore important to understand how they are programmed and especially, how they operate.
    • Any hardware device that can be programmed uses two processes:
      • Sensor
      • Actuator
  • 4. Sensor
    • Any device that converts input from the environment into a digital signal.
    • The signal is then interpreted by the software.
  • 5. Actuator
    • An output device that performs a mechanical action.
    • Actuators receive digital signals from software.
  • 6. Processing a Data Stream
    • What is a Data Stream?
    • A packet of binary data consisting of a header, data characters and a trailer.
    • For example:
    • Header Data Trailer
    • 010101 | 101010100 | 0101010
    • The information contains the data and a check to see if it is correct.
  • 7. Processing a Data Stream
    • What is in the header?
    • Specifies how much data is to be transmitted.
    • Contain error checking data such as:
        • Parity Checking
        • CRC 16
    • Specifies the device in which it is coming from.
  • 8. Processing a Data Stream
    • What is in the data section?
    • Includes control characters i.e SHIFT + B
    • All subsequent instructions to be processed by the CPU.
  • 9. Processing a Data Stream
    • What is in the trailer section?
    • Data bits that end the block.
    • Error checking bits
    • Memory clear instructions.
  • 10. Processing a Data Stream
    • Recognising and stripping control Characters
    • Control characters are represented by the ASCII values 0 – 31 and are typed while pressing the control key.
  • 11. Processing a Data Stream
    • Counting the Data Characters
    • The header field will normally contain all required information relating to the size of data packets.
  • 12. Processing a Data Stream
    • Extracting Data
    • Once the header and trailer have been removed, the hardware within the CPU will extract the data, and relevant software will carry out the instructions.
  • 13. Keyboard Example
    • How a keyboard transmits data?
    • Pressing a key causes a change to take place in the amount of current flowing through key circuits.
    • A microprocessor sends a signal relating to the pressed key along a cable port notifying the BIOS.
  • 14. Keyboard Example
    • The BIOS translates the codes into ASCII and that particular character or command is stored in memory.
  • 15. Control Systems
    • These are systems that include hardware devices, software and especially the use of sensors and actuators.
    • There are two broad categories of control systems:
        • Open Control Systems
        • Closed Control Systems
  • 16. Open Control Systems
    • These systems do not react to their environment.
    • These systems normally require a user to activate the actuator.
    • E.g. Hotel Door Lock.
  • 17. Closed Control Systems
    • These systems actually react to their environment.
    • This system uses sensors and programmed structures to control the actuators.
    • For Example:
      • Anti-Lock Breaking System
  • 18. Question 1
    • A robotic moon car is designed to use digital controls. The motor of the car receives the following commands from a user.
    Motor off. Stop Turns left X deg LeftX Turns right X deg RightX Moves in straight line at X speed. StraightX Trailer <-T Header ->H
  • 19. Question 1
    • The speed for the car can range from + 100 (Fastest) to -100 (Backward)
    • 1.) Identify the category of control system.
    • 2.) Identify the problems with the following instruction:
    • ->HStraight20StopRight90Forward10->H
    • 3.) Construct a data stream to carry out the following tasks:
    • Move forward 30
    • Move left 45, move forward 80
    • Move right 20, backward -20, stop
  • 20. Question 2
    • Complete the following text book questions:
    • SET 10F
    • Question 11
    • Question 13
    • Question 14