Execution and Observation - 5.3.4 | Experiment No. 8: 8051 Microcontroller - Serial Communication and Interrupts | Microcontroller Lab
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5.3.4 - Execution and Observation

Practice

Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Introduction to Serial Communication

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0:00
Teacher
Teacher

Today we're going to explore serial communication using UART. Can anyone share what they understand by UART?

Student 1
Student 1

UART stands for Universal Asynchronous Receiver/Transmitter, right? It's used for serial communication.

Teacher
Teacher

Exactly! UART allows data to be transmitted one bit at a time, which is efficient for many applications. Do you recall why this might be important?

Student 2
Student 2

Because it uses fewer pins and can work over long distances?

Teacher
Teacher

Spot on! Now let’s remember the data frame structure. Can anyone help me list the components of a data frame?

Student 3
Student 3

I remember it includes a start bit, data bits, an optional parity bit, and stop bits.

Teacher
Teacher

Great job! Keeping this structure in mind is crucial. It ensures accurate communication. Let’s summarize: UART compresses multiple bits into a single stream, which is vital for effective data transfer.

Configuration of UART in 8051

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0:00
Teacher
Teacher

Let’s dive into configuring the UART in the 8051. Who can tell me what registers we need for configuration?

Student 4
Student 4

We need to use the SBUF for data transmission and reception, and the SCON to control the serial port settings.

Teacher
Teacher

Exactly! The SCON register allows us to set the mode of operation, and we typically use Mode 1 for an 8-bit variable baud rate. What is the formula for calculating the baud rate in this mode?

Student 1
Student 1

The formula is Baud Rate = (Oscillator Frequency / 12) / (32 * (256 - TH1)).

Teacher
Teacher

That’s correct! Remember to configure Timer 1 to achieve the desired baud rate. Let's summarize: The ability to configure UART properly ensures effective communication between devices.

Understanding Interrupts

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0:00
Teacher
Teacher

Next, we’re going to talk about interrupts. Who can explain what an interrupt is?

Student 2
Student 2

An interrupt is a signal that pauses the main program execution so it can execute a special routine.

Teacher
Teacher

Exactly! They allow for efficient event handling. The 8051 has multiple interrupt sources — can anyone name a few?

Student 3
Student 3

There’s External Interrupt 0, Timer 0 Overflow, and Serial Port Interrupt.

Teacher
Teacher

Well done! And when we configure these interrupts, what registers do we work with?

Student 4
Student 4

We work with the IE and IP registers to enable and set priorities for interrupts.

Teacher
Teacher

Great summary! Interrupts are essential for responsive applications where external events need quick reactions. Let's quickly recap: Configuration of interrupts allows your microcontroller to respond instantly to events.

Practical Implementation of External Interrupts

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0:00
Teacher
Teacher

Now, let's talk about how to set up an external interrupt in our project. How do we connect the push button to the 8051?

Student 1
Student 1

We connect the push button to the overlineINT0 pin and ground it using a pull-up resistor.

Teacher
Teacher

Right! And in your code, how do you tell the 8051 that you want to enable that external interrupt?

Student 2
Student 2

By using the EX0 bit in the IE register and configuring the edge trigger with IT0.

Teacher
Teacher

Exactly! So now that we can see how to handle external events, what happens inside the ISR when an interrupt occurs?

Student 4
Student 4

The ISR will execute and can perform tasks like toggling an LED if that’s what we coded it to do.

Teacher
Teacher

Perfect! Recapping: External interrupt handling enables responsive designs, crucial in real applications.

Timer Interrupts and Periodic Tasks

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0:00
Teacher
Teacher

Finally, let’s discuss timer interrupts. why might we want to use a timer interrupt?

Student 1
Student 1

We can use it for tasks that need to happen periodically, like updating a display or counter.

Teacher
Teacher

Correct! Can anyone tell me how we configure Timer 0 for these interrupts?

Student 3
Student 3

We set it in Mode 1 and specify TH0 and TL0 values for the desired delay.

Teacher
Teacher

Spot on! And what’s the computation behind setting those timer values?

Student 4
Student 4

We calculate it as 65536 minus the desired time multiplied by the oscillator frequency divided by 12.

Teacher
Teacher

Exactly! Remember, these calculations allow for accurate timing in our projects. To summarize: Timer interrupts are crucial for scheduling tasks and enhancing functionality in embedded systems.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section details the execution and observation of experiments related to serial communication and interrupt handling using the 8051 microcontroller.

Standard

The section describes the aim, objectives, theoretical background, and practical execution of an experiment involving the 8051 microcontroller for serial communication and interrupt handling. It covers the configuration of the UART, external interrupts, and timer interrupts, along with the expected observational results following the execution of each part.

Detailed

Execution and Observation

Experiment Objectives

This section aims to help students understand the implementation of serial communication (UART) and interrupt handling mechanisms using the 8051 microcontroller. The primary objectives include explaining serial communication basics, configuring UART, differentiating between polling and interrupts, as well as handling both external and timer interrupts.

Key Concepts Covered

  1. Serial Communication (UART): Explanation of UART functionalities, baud rates, and the structure of data frames involved.
  2. Interrupt Concepts: Exploration of various interrupt sources in the 8051, including their enablement and handling through Interrupt Service Routines (ISRs).
  3. Practical Application: The procedure consists of three distinct parts focusing on serial communication, external interrupt handling, and timer interrupt for periodic tasks.

Importance

Understanding these concepts is critical for developing embedded systems capable of real-time interaction and data handling efficiently. Through this experiment, students gain hands-on experience with the foundational principles that govern effective microcontroller interactions, setting the stage for more advanced applications in embedded programming.

Audio Book

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Part A: Serial Communication (Transmit and Receive)

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  1. Hardware Setup:
  2. Connect the 8051 development board's serial port (TxD - P3.1, RxD - P3.0) to the PC via a USB-to-Serial converter. Ensure correct RxD-TxD cross-connection (TxD of 8051 to RxD of PC, RxD of 8051 to TxD of PC).
  3. Power on the 8051 board.
  4. Software Setup (PC):
  5. Open a terminal emulator (e.g., PuTTY).
  6. Configure the serial port settings:
    • Serial line: Select the COM port assigned to your USB-to-Serial converter (check Device Manager).
    • Speed (Baud): Set to 9600 (or desired baud rate).
    • Data bits: 8
    • Stop bits: 1
    • Parity: None
    • Flow control: None
  7. C Program for Serial Communication (Transmit & Receive Loopback):
  8. Aim: Transmit a string "Hello from 8051!" and then echo back any character received from the PC.
  9. Compilation and Flashing:
  10. Compile the C code using Keil uVision. Resolve any errors.
  11. Flash the generated .hex file to the 8051 microcontroller using your programmer.
  12. Execution and Observation:
  13. Open the terminal emulator.
  14. Reset the 8051 board.
  15. Observe the "Hello from 8051!" message appearing on the terminal.
  16. Type characters on your PC's keyboard within the terminal. Observe if the 8051 echoes back the characters you type.

Detailed Explanation

In this part of the experiment, we set up the hardware and software needed for serial communication. This involves connecting the microcontroller board to a PC using a USB-to-Serial converter with correct connections for transmit and receive lines. After powering on the board, we use terminal emulator software to configure the serial port settings, which include specifying the baud rate and data bits.

Next, we write a simple C program that sends a message from the microcontroller to the terminal and subsequently echoes any typed characters back from the terminal to the microcontroller. This is compiled and uploaded to the microcontroller.

Upon execution, we observe that the message appears in the terminal, and any keystrokes sent from the terminal are echoed back by the microcontroller, confirming successful serial communication.

Examples & Analogies

Think of this process like sending messages back and forth through a walkie-talkie. The microcontroller is like one person, sending out a message ('Hello from 8051!'). The terminal on the PC is like another person, who can respond by speaking into the walkie-talkie after receiving the original message. The setup needs to ensure that both individuals can hear each other clearly, which is similar to ensuring correct baud rate and settings for effective communication.

Part B: External Interrupt Handling

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  1. Hardware Setup:
  2. Connect a push button to the overlineINT0 pin (P3.2) of the 8051. Connect the other end of the button to ground. Use a pull-up resistor (e.g., 10k Ohm) for P3.2 if the internal pull-up is not strong enough or disabled.
  3. Connect an LED with a current-limiting resistor (e.g., 220 Ohm) to a general-purpose I/O pin (e.g., P1.0).
  4. C Program for External Interrupt:
  5. Aim: Toggle an LED connected to P1.0 every time a button connected to overlineINT0 (P3.2) is pressed.
  6. Compilation and Flashing: Compile and flash the code to the 8051.
  7. Execution and Observation:
  8. Press the button connected to P3.2.
  9. Observe the LED connected to P1.0. Each press (falling edge) should toggle the LED's state (ON to OFF, OFF to ON).

Detailed Explanation

This segment focuses on using an external interrupt to control an LED with a push button. First, we set up the hardware by connecting a push button to an external interrupt pin and linking an LED to a general-purpose I/O pin. This way, each time the button is pressed, it generates an interrupt signal that triggers a specific action.

In the C program, we create an Interrupt Service Routine (ISR) that toggles the LED every time an interrupt occurs from the button press. After compiling and uploading this program to the microcontroller, we press the button and observe the LED toggle on and off, indicating that the interrupt handling is functioning correctly.

Examples & Analogies

Imagine this setup as a doorbell (the button). When someone presses the doorbell, it rings (generates an interrupt), and this action makes you aware that someone is at the door (the LED toggles). Just like you react to the sound of the doorbell, the microcontroller reacts to the button press and changes the state of the LED accordingly.

Part C: Timer Interrupt for Periodic Task

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  1. Hardware Setup:
  2. Connect an LCD (e.g., 16x2 LCD) to the 8051's ports (typically P2 for data, and some P0/P1 pins for control RS, RW, E). (Assume LCD interfacing is already familiar or use a pre-wired setup on the trainer kit).
  3. C Program for Timer Interrupt and LCD Update:
  4. Aim: Use Timer 0 interrupt to update a counter on an LCD display every 100 milliseconds.
  5. Compilation and Flashing: Compile and flash the code to the 8051.
  6. Execution and Observation:
  7. Observe the LCD display. A counter should be incrementing approximately every 100 milliseconds.
  8. Verify the periodicity of updates. If an oscilloscope is available, you could toggle an unused pin in the ISR to visually confirm the interrupt frequency.

Detailed Explanation

In this part, we set up an LCD and program the microcontroller to utilize Timer 0 for generating periodic interrupts. The timer is configured to create an interrupt every 100 milliseconds, and the corresponding ISR is written to increment a counter.

We've established that the LCD will display this counter, updating every time the timer interrupt occurs. When we run the program, we can see the counter incrementing on the LCD at a regular interval, effectively demonstrating the use of timer interrupts to perform periodic tasks.

Examples & Analogies

Think of this as a regularly scheduled meeting reminder (the timer). Every 100 milliseconds, like a regular clock chime, you get reminded to check the LCD to update the count. It’s like having a digital clock that ticks every second, and you glance to see the time changing each tick, without having to manually check it.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Serial Communication (UART): Explanation of UART functionalities, baud rates, and the structure of data frames involved.

  • Interrupt Concepts: Exploration of various interrupt sources in the 8051, including their enablement and handling through Interrupt Service Routines (ISRs).

  • Practical Application: The procedure consists of three distinct parts focusing on serial communication, external interrupt handling, and timer interrupt for periodic tasks.

  • Importance

  • Understanding these concepts is critical for developing embedded systems capable of real-time interaction and data handling efficiently. Through this experiment, students gain hands-on experience with the foundational principles that govern effective microcontroller interactions, setting the stage for more advanced applications in embedded programming.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • In a UART configuration, setting the baud rate to 9600 bps allows for effective communication between the 8051 and a PC.

  • An external interrupt can be configured to toggle an LED upon a button press, showcasing the responsiveness of interrupt handling.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • When communicating with a UART's might, Data flows smoothly, day and night.

📖 Fascinating Stories

  • Imagine a busy post office (the 8051) that only sends one letter (bit) at a time. Each postman (UART) waits for the right moment to deliver the message, ensuring clarity and accuracy.

🧠 Other Memory Gems

  • To remember UART settings: 'BOLD' - Baud rate, Optional bits, Levels need to be defined.

🎯 Super Acronyms

UART = Unified Asynchronous Reception and Transmission.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: UART

    Definition:

    Universal Asynchronous Receiver/Transmitter; a hardware component that enables serial communication by converting parallel data from a microcontroller to serial data.

  • Term: Baud Rate

    Definition:

    The rate at which data is transmitted in bits per second (bps) over a communication channel.

  • Term: Data Framing

    Definition:

    The structure of transmitted serial data which includes a start bit, data bits, optional parity bit, and stop bits.

  • Term: Interrupt

    Definition:

    A signal that temporarily halts the normal execution of a program, allowing the CPU to execute a designated Interrupt Service Routine (ISR).

  • Term: ISR

    Definition:

    Interrupt Service Routine; a function executed in response to an interrupt, typically containing the code to handle the interrupt event.

  • Term: 8051

    Definition:

    An 8-bit microcontroller family popular for embedded systems, known for its integrated peripherals including UART and multiple timers.