Programming Hardware Devices

Software Developers View of Hardware

Programming Hardware Devices

What does this mean?

Computers usually interact with outside sources for input and output: CD-ROM Mouse Keyboard Scanner Monitor.

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

Sensor

Any device that converts input from the environment into a digital signal.

The signal is then interpreted by the software.

Actuator

An output device that performs a mechanical action.

Actuators receive digital signals from software.

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.


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.


What is in the data section? Includes control characters i.e SHIFT + B All subsequent instructions to be processed

by the CPU.


What is in the trailer section? Data bits that end the block. Error checking bits Memory clear instructions.


1. Recognising and stripping control Characters

Control characters are represented by the ASCII values 0 – 31 and are typed while pressing the control key.


2. Counting the Data Characters The header field will normally contain all

required information relating to the size of data packets.


3. 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.

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.

Keyboard Example

The BIOS translates the codes into ASCII and that particular character or command is stored in memory.

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

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.

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

Question 1

A robotic moon car is designed to use digital controls. The motor of the car receives the following commands from a user.

->H Header

<-T Trailer

StraightX Moves in straight line at X speed.

RightX Turns right X deg

LeftX Turns left X deg

Stop Motor off.

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

Question 2

Complete the following text book questions:

SET 10F

Question 11

Question 13

Question 14

Technology

Programming Hardware Devices