Micro computers


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Last Updated:	March 21, 2004

WANT TO LEARN HOW TO MAKE A MICRO COMPUTER?

This website is intended for all people at all ages. This is made simple and understandable in order for non-technical people to understand. Microcomputer is also known as microcontrollers. The microcontrollers discussed here is based from Microchip known as PIC microcontrollers. Any information that is in this website is maintained by the webmaster. Please feel free to leave a comment or any suggestion that might be useful to others.

Understanding the Basics...

You should know at least one programming language (Assembly or C-language minimum) and a little of electronics.

Microcontrollers are hidden inside a surprising number of products these days. For example, if your microwave oven has an LED or LCD display and a keypad, it contains a microcontroller. All modern automobiles contain at least one microcontroller, and can have as many as six or seven: The engine is controlled by a microcontroller, as are the antilock brakes, the cruise control and so on. Any device that has a remote control almost certainly contains a microcontroller: TVs, VCRs and high-end stereo systems all fall into this category. Nice SLR and digital cameras, cell phones, camcorders, answering machines, laser printers, telephones (the ones with caller ID, 20 number memory, etc.), pagers, feature-laden refrigerators/dishwashers/ovens/washer/dryers (the ones with displays and keypads)... You get the idea. Basically any product or device that interacts with its user has a microcontroller buried inside.

Defining a Microcontroller
A microcontroller is a computer. All computers - whether we are talking about the desktop computer you are using to read this article, or a large mainframe computer in a major corporation, or a microcontroller - have several things in common. For example, all computers have a CPU (Central Processing Unit) that "executes programs". If you are sitting at a desktop computer right now reading this article, the CPU in that machine is executing a program that implements the WWW browser you are using to see this article. The CPU loads the program from somewhere. On your desktop machine the browser program is loaded from the hard disk. The computer has some RAM (Random Access Memory) where it can store "variables". And the computer has some input and output devices so it can talk to people. On your desktop machine the keyboard and mouse are input devices and the monitor and printer are output devices. A hard disk is an I/O device - it handles both input and output.

The desktop computer you are using is a "general purpose computer" that can run any of thousands of programs. Microcontrollers are "special purpose computers." Microcontrollers do one thing well. There are a number of other common characteristics that define microcontrollers. If a computer matches a majority of these characteristics, then you can call it a "microcontroller":

Microcontrollers are "embedded" inside some other device (often a consumer product) so that they can control the features or actions of the product. Another name for a microcontroller, therefore, is "embedded controller".
Microcontrollers are dedicated to one task and run one specific program. The program is stored in ROM (Read-only memory) and generally does not change.
Microcontrollers are often low-power devices. A desktop computer is almost always plugged into a wall socket and might consume 50 watts of electricity. A battery-operated microcontroller might consume 50 milliwatts.
A microcontroller has a dedicated input device and often (but not always) has a small LED or LCD display for output. A microcontroller also takes input from the device it is controlling and controls the device by sending signals to different components in the device. For example, the microcontroller inside a TV takes input from the remote control and displays output on the TV screen. The controller controls the channel selector, the speaker system and certain adjustments on the picture tube electronics such as tint, brightness, etc. On the other hand, the engine controller in a car takes input from sensors like the oxygen and knock sensors and controls things like fuel mix and spark plug timing. A microwave oven controller takes input from a keypad, displays output on an LCD display and controls a relay that turns the microwave generator on and off.
A microcontroller is often small and low cost. The components are chosen to minimize size and to be as inexpensive as possible.
A microcontroller is often, but not always, "ruggedized" in some way. The microcontroller controlling a car's engine, for example, has to work in temperature extremes that a normal computer generally cannot handle. For example, a car's microcontroller in Alaska has to work fine in -30 degree F weather, while the same microcontroller in Death Valley might be operating at 120 degrees F. When you add the heat naturally generated by the engine the temperature could go as high as 150 or 180 degrees in the engine compartment. On the other hand, a microcontroller embedded inside a VCR hasn't been ruggedized at all.

The actual processor used to implement a microcontroller can vary widely. For example, the cell phone shown on this page contains a Z-80 processor. The Z-80 is an 8-bit microprocessor developed in the 1970s and originally used in "home computers" of the time. The Garmin GPS shown on the the HSW GPS page contains a low-power version of the Intel 80386 I am told. The 80386 was originally used in desktop computers.

In many products such as microwave ovens, the demand on the CPU is fairly low and price is an important consideration. In these cases manufacturers turn to dedicated microcontroller chips - chips that were originally designed to be low-cost, small, low-power embedded CPUs. The Motorola 6811 and Intel 8051 are both good examples of such chips. There is also a line of popular controllers called "PIC microcontrollers" created by a company called Microchip. By today's standards these CPUs are incredibly minimalistic, but they are extremely inexpensive when purchased in large quantities and can often meet the needs of a device's designer with just one chip. A typical low-end microcontroller chip might have 1,000 bytes of ROM and 20 bytes of RAM on the chip, along with eight I/0 pins. In large quantities the cost of these chips can sometimes be just pennies. You certainly are never going to run Microsoft Word on such a chip - Microsoft Word requires perhaps 30 megabytes of RAM and a processor that can run millions of instructions per second to operate. But then you don't need Microsoft Word to control a microwave oven either. With a microcontroller you have one specific task you are trying to accomplish and low-cost, low-power performance is what is important.

For the last 2 years, I have been working with microcontrollers specifically with Microchip PIC16F877. I have compiled these projects and made create a prototype. If you are interested, pictures will be available soon, I just need to upload the pictures. The project is acquiring analog signals in a remote area.

Letters from the Author:

We have a lot of micro controller to choose from (eg. Atmel, Intel, Motorola, Parallax, PIC). My focus is only the Microchip PIC which is PIC16F877. PIC16F877 has many peripheral features, you can communicate with your PC or other devices which uses the Universal Synchronous Asynchronous Receiver Transmitter (USART), acquire analog signals, and interface with other chips. I also get hold PIC16F84 since the code are mostly the same and some of my classmates did use this device. I get involved with microcontrollers when I was doing my thesis which uses PIC16F877 and a powerline modem (ST7537). Below is a more descriptive about the project which fall under the POWERLINE. If you want to learn about microcontrollers, you should learn how to program. There are two ways on how to program a microcontroller, one is the C - Language and the other one is the Assembly Language. I proposed to use Assembly Language if you are a beginner, if you are familiar with it then its time for you to use the C Language. I learned the longest one which is the Assembly Language because it is all supplied by Microchip and the documents supplied by them is understandable since it is free. You can ask a CD from them and it will be delivered right next to your doorstep just visit their website

http://www.microchip.com

POWERLINE COMMUNICATION

The project objective is to monitor temperature and pressure at the same time on a different room. Below is a useful website to read about the powerline modem used in the project

http://www.hth.com/plm-24/plm-24.htm

Useful Sites:

Microcontroller (for PIC only!!!)

Beginner (What things you must know and what things you must need)
Amateur (Templates)
Experts (Complicated)

Routines

note: all information enclosed here are compiled by MPLAB and are dot ASM format

Universal Synchronous Asynchronous Receiver Transmitter (USART)
Analog to Digital Converter (ADC)
Serial In Parallel Out (SIPO)
Seven Segment
Power Line Modems
Dual Tone Multi Frequency (DTMF)

THE BEST THINGS IN LIFE IS FREE

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