LED Interfacing with 8051 In Advance Level

Introduction:

     If you are looking for a beginners guide on “How to start with 8051 Microcontroller”, here in this article I will show you how to work with 8051 microcontroller practically. I am not going into detail of “What is 8051 microcontroller”  or “How to write a c-program” etc., but the scope of this article is to tell about the hardware and software which are needed to work with microcontroller and how to use them.

     To get started with designing mega projects or electronics innovation the understanding of basic and simple projects is important. This will get familiarized with 8051 Microcontroller and also the designing environment. LED Interface with 8051 is one of the basic projects.  Therefore, shall be looking at the very basic project, which is interfacing LED with 8051 and then moving towards mega projects.

Table of Content:
1.   List of Inventories
     1.1 Hardware Requirement     
     1.2 Software Requirements 
     1.3 Brief Introduction of component and calculate resistance 

2.   System Modelling  
     2.1 Circuit Diagram
     2.2  Source Code Programming 
            2.2.1  LED Interfacing with 8051
                     2.2.1.1 How to Edit, Compile code and get .hex  file
            2.2.2 Multiple LED Interfacing with 8051
            2.2.3 Multiple LED Light Interfacing with 8051
            2.2.4 Traffic light Controlling System

1.List of Inventories:

1.1     Hardware Requirements:        

   I.   Resistor : 220hm

          II.  Light Emitting Diode: 5 mm

          III.  Power Supply: 9 to 12 Vdc & <= 1A 

          IV.  Connectors: Male to female 

  V. 8051microcontroller

 VI. 11.0592 Mhz Crystal Oscillator

VII. 33pf capacitor - 2

1.2     Software and Library requirements:
  1) Keil Software
 2) Proteus Software 

1.1       Brief introduction of the component:

1)       8051: The Intel 8051 is an 8-bit microcontroller which means that most available operations are limited to 8 bits. There are 3 basic "sizes" of the 8051: Short, Standard, and Extended. The Short and Standard chips are often available in DIP (dual in-line package) form, but the Extended 8051 models often have a different form factor, and are not "drop-in compatible". All these things are called 8051 because they can all be programmed using 8051 assembly language, and they all share certain features (although the different models all have their own special features).

Some of the features that have made the 8051 popular are:

·        4 KB on chip program memory.

·        128 bytes on chip data memory(RAM)

o   32 bytes devoted to register banks

o   16 bytes of bit-addressable memory

o   80 bytes of general-purpose memory

·        4 register banks.

·        128 user defined software flags.

·        8-bit data bus

·        16-bit address bus

·        16 bit timers (usually 2, but may have more, or less).

·        3 internal and 2 external interrupts.

·        Bit as well as byte addressable RAM area of 16 bytes.

·        Four 8-bit ports, (short models have two 8-bit ports).

·        16-bit program counter and data pointer.

·        1 Microsecond instruction cycle with 12 MHz Crystal.

Variants of the 8051 may also have a number of special, model-specific features, such as UART, ADC, Op_Amps, etc., making it an even more powerful microcontroller.

Basic Pins:

1. PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller’s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)
2. PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only connect a crystal at these pins to provide clock pulses to the circuit.
3. PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V 500mA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.
4. PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If external memory is connected then PIN 31, also called EA/VPP, should be connected to ground to indicate the presence of external memory. PIN 30 is called ALE (address latch enable), which is used when multiple memory chips are connected to the controller and only one of them needs to be selected.We will deal with this in depth in the later chapters. PIN 29 is called PSEN. This is "program store enable". In order to use the external memory it is required to provide the low voltage (0) on both PSEN and EA pins.
5. Pin 29: If we use an external ROM then it should have a logic 0 which indicates Micro controller to read data from memory.
6. Pin 30: This Pin is used for ALE that is Address Latch Enable. If we use multiple memory chips then this pin is used to distinguish between them.It is activated periodically with a constant rate of 1/6th of oscillator frequency. This Pin also gives program pulse input during programming of EPROM.
7. Pin 31: If we have to use multiple memories then by applying logic 1 to this pin instructs Micro controller to read data from both memories first internal and afterwards external.

Ports

There are 4 8-bit ports: P0, P1, P2 and P3.

PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or additional functions associated with them based upon the context of their usage.The port 1 output buffers can sink/source four TTL inputs. When 1s are written to portn1 pins are pulled high by the internal pull-ups and can be used as inputs.

PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2 external counter inputs, read and write pins for memory access.

PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P2 will act as an address bus in conjunction with PORT P0 to access external memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1

PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P0 acts as a multiplexed address and data bus that can be used to access external memory in conjunction with PORT P2. P0 acts as AD0-AD7

PORT P10: asynchronous communication input or Serial synchronous communication output.

PIN 11: Serial Asynchronous Communication Output or Serial Synchronous Communication clock Output.

Oscillator Circuits

The 8051 requires an external oscillator circuit. The oscillator circuit usually runs around 12 MHz, although the 8051 (depending on which specific model) is capable of running at a maximum of 40 MHz. Each machine cycle in the 8051 is 12 clock cycles, giving an effective cycle rate at 1 MHz (for a 12 MHz clock) to 3.33 MHz (for the maximum 40 MHz clock). The oscillator circuit generates the clock pulses so that all internal operations are synchronized.

One machine cycle has 6 states. One state is 2 T-states. Therefore one machine cycle is 12 T-states. Time to execute an instruction is found by multiplying C by 12 and dividing product by Crystal frequency.

T=(C*12d)/crystal frequency

What is design re-usability?

There are a lot of semiconductor companies that manufacture logic devices like CPUs, microprocessor, microcontrollers and so on. The process of development of these technologies is often time-consuming and needs a lot of investment.

Let’s say Company A invests a lot of time and money in developing a state of the art controller from the ground up. There are a lot of underlying processes which come together to make a controller. For example, designing the architecture. Once Company A has developed, tested and released their finished product, they sell the license of the underlying technologies used to build that particular controller of theirs, to other companies. So if Company B buys this license from Company A, they don’t have to do all the work from scratch. They can just use Company A’s underlying technology to build their own customized controller.

The underlying technologies that are licensed are called Intellectual Property (IP) Cores. Using popular IP cores maintains consistency and people like us get a lot of options to work on without experiencing drastic changes in usability. If every company had its own architecture, it would be quite difficult to learn those every time you wanted to try a new microcontroller. An excellent example of this are the Exynos chips from Samsung and the AX chips from Apple. They both use ARM IP cores.

The 8051 IP cores are free to use. The actual microcontrollers are incredibly cheap to buy. They are smaller and consume less power than 32 bit ARM cores. There is a large community of people who are familiar with the architecture. These are just some of the reasons why the 8051 is still popular.

System design metrics

When we design an embedded system, there are a few things that need consideration. It is the job of an embedded systems engineer to make sure that all of the following parameters (and more, as we will see later in this course) are considered.

• Processing power
• Reliability
• Power consumption
• Cost
• Time to prototype & time to market
• Maintainability

• Processing Power 

Based on the complexity of the software, a system requires a certain amount of computing power. It is necessary to find the right amount of processing power, not too less and definitely not more than required. 8051s have enough variants that provide processing power from 1 MIPS (Original 8051) to 450 MIPS (Million Instructions Per Second)

• Reliability

An embedded system needs to be tested and validated thoroughly. This stage usually takes time and adds to the cost.The 8051 variants available in the market have been tested rigorously, thanks to its popularity and free of cost IP cores.

• Power consumption

It is imperative to treat power as a scarce resource while designing an embedded system. You are always expected to develop a system that has just enough power to be fully operational. The life of a system’s battery depends on the power consumed by it.

• Costs

The cost is usually considered way before the actual designing of an embedded system even begins. The cost of the project is one of the biggest things to be considered before designing a project.The 8051 has free IP cores, and the actual chips are inexpensive.

• Time to prototype and time to market

Time equals higher costs and is usually mostly spent on implementing the core functionality in a working prototype, scaling it and testing it. Time to market is the time required to make a system ready for marketing.Since the 8051 has a simple architecture, its testing is easy too.

• Maintainability 

The ease with which a system can be maintained or modified after its commercial release. Especially by designers who were not involved in the original designing of the system. 

2)       LED Matrix :

These matrix can be made by circuiting 64 LEDs, however that process is time consuming. Now a day they are available in compact forms as shown in below image. These compact modules are available in different sizes and many colors. The cost of module is same as cost of 64 LEDs, so for hobbyists this is easiest to work on.The bare LED matrix has 16 pin outs with 8 common positive and another 8 common negative. For connecting this matrix directly to a UNO, we need to spare 16 pins on the UNO. With the output pins low on UNO, we cannot spare 16 PINS. So we need to connect this matrix to a driver chip. This driver chip along with matrix comes as a set which is shown in below figure.

IDE for Programming

I am assuming that you are aware about the basic electronics components, wires, breadboard, battery etc, so I am directly heading to 8051 Microcontroller.

Now first we need a C program to run microcontroller, so that we can program it and it will work according to program. So we need an IDE (Integrated development environment) to write and compile the program, there are many editor available but unarguably the best IDE is “keil uVision IDE”. In Keil uvision you can write, compile, debug and run a program. There are the steps to use Keil uvision:

1. Download latest keil uvision4 and install the program.

2. Go to Project and select ‘New uVision Project’, give it a name and save it. You will find ‘Target 1’ and ‘Source Group 1’ folder structure in the left side.

3. Right click on Target 1, select “Options for Target Target 1”, click on Output tab and check the checkbox ‘Create HEX file’ then click OK.

1.   Click on File menu and click on ‘New’, write c program and save it with .c extension like ‘led_blinking.c’ (usually in same folder in which we create uVision project)

2.  Right click on ‘Source Group 1’ select ‘Add files to Group Source Group 1’ and select your c program file and click ‘Add’ then click ‘Close’.

3. Now go to Project menu and click on ‘Rebuild all target Files’ or click on button as shown in above figure. In output window, you can check for any Error and Warning. It also create HEX file in same folder as c program file. We need this HEX file to program 8051 chip, explained in next section.

So at the end of this section, we have the HEX file of c program which we want to run through 8051 microcontroller.

2. System modelling:

2.1 Circuit Diagram:

    2.2  Working of project
      This is a simple project which will make LED blink. The basic idea is to turn on LED and after some time turn it off. The anode of the LED is connected through a 330 ohms resistor to pin 13 of Arduino and the cathode also through the 330 ohms resistor to GND. When the command to turn on the LED is given through code, a +5v is supplied to the anode of the LED and this makes it light up. Also when the command to turn off the LED is given, it takes it back to 0v thereby turning the LED off. The code is given below.

More About 

    I. How to select Board ?

   II. How to compile program ?

   III. How to add sensor/module library in proteus software?

2.3 Result:
Published by, Electronics with shreyash:

 To Download the code click here

2.2.2 Multiple LED Interfacing with Arduino

Introduction:

It is Similar to interfacing single LED just required to declare multiple LED pin as a OUTPUT and adjust the all LED blinking sequence as per choice of delay between each .

2.3 Result:

Published by, Electronics with shreyash :

 To Download the code click here

2.2.3 Multiple LED  lights Interfacing with Arduino

Introduction:

It is Similar to interfacing single LED just required to declare multiple LED pin as a OUTPUT and adjust the all LED blinking sequence as per choice of delay between each .

2.3 Result:

Published by, Electronics with shreyash :

 To Download the code click here

2.2.4 Traffic Light control system

Introduction: Traffic Lights or Traffic Signals are signalling devices that are used to control the flow of traffic. Generally, they are positioned at junctions, intersections, ‘X’ roads, pedestrian crossings etc. and alternate the priority of who has to wait and who has to go. The traffic lights will provide instructions to the users (drivers and pedestrians) by displaying lights of standard color. The three colors used in traffic lights are Red, Yellow and Green.The system must be used to control the traffic lights for smooth and safe movement of traffic. These control systems consists of Micro-controllers with clockwork mechanisms or modern solid state computerized systems with easy setup and maintenance.

2.3 Result:

Published by, Electronics with shreyash :

 To Download the code click here

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