Chapter 1: Introduction to Microcontrollers & PIC24FJ64GA002¶

Section 1: What is a Microcontroller?¶

A microcontroller is a compact, self-contained computer system built onto a single integrated circuit. It includes:

A CPU (Central Processing Unit)
Memory (Flash and RAM)
A set of peripherals (I/O ports, timers, ADCs, serial comms)

These components allow the microcontroller to interact with the real world — sensing, computing, and controlling things like motors, lights, sensors, and displays.

Microcontroller Block Diagram¶

The diagram below shows a typical microcontroller architecture.

As shown: - The CPU communicates with peripherals through buses - Modules like UART, SPI, ADC, and timers are all built-in - Flash stores the program, and RAM stores runtime variables

Unlike general-purpose computers, microcontrollers are built for dedicated control tasks — not multitasking or user interaction.

Key Characteristics¶

🔹 Small footprint: Ideal for embedded systems with limited space
🔹 Real-time responsiveness: Handles time-sensitive tasks predictably
🔹 Integrated I/O: No need for external chips to communicate
🔹 Low power: Great for battery-powered devices
🔹 Cost-effective: Perfect for mass production and consumer products

Microcontrollers are the foundation of most embedded systems — from smart home devices to industrial automation.

Section 2: Overview of the PIC24FJ64GA002¶

For this textbook, we’ll be working with the PIC24FJ64GA002, a 16-bit microcontroller developed by Microchip.

This device strikes a great balance between simplicity and power — making it ideal for students and embedded systems developers alike.

Key Features¶

Feature	Value
Core	16-bit modified Harvard
Clock Speed	Up to 32 MHz
Program Flash	64 KB
RAM	8 KB
I/O Pins	21
Timers	5 (16-bit and 32-bit capable)
ADC Channels	10-bit, 13 input channels
UART / SPI / I2C	2 UARTs, 2 SPI, 1 I2C

Datasheet Reference: PIC24FJ64GA002 Datasheet (Microchip)

Why This Chip?¶

Widely supported in MPLAB X IDE and the XC16 compiler
Features common peripherals used in real-world systems
Has enough complexity to teach important concepts without being overwhelming
Low-cost and easy to prototype with (available on dev boards)

You’ll see this microcontroller referenced throughout the book — from I/O programming to advanced peripheral control.

Section 3: The Development Environment¶

To write, compile, and test code for the PIC24FJ64GA002, we use Microchip’s official toolchain:

MPLAB X IDE¶

MPLAB X is an Integrated Development Environment (IDE) that supports Microchip’s entire family of devices, including PIC24.

Features project management, code editing, and debugger integration
Runs on Windows, macOS, and Linux
Allows simulation, breakpoints, memory inspection, and more

Download: MPLAB X IDE – Microchip

XC16 Compiler¶

Microchip’s XC16 is a C compiler tailored for 16-bit devices like the PIC24 family.

Converts your C code into binary .hex files for flashing
Works directly inside MPLAB X
Supports optimization levels for size, speed, and debugging

In this book, we’ll stick to C and inline assembly where needed — all compiled using XC16.

Simulators and Debuggers¶

You can: - Simulate logic (LEDs, registers, timing) using MPLAB’s built-in simulator - Flash code to real hardware using tools like PICkit 3/4 or Curiosity boards

Later in this book, we’ll introduce MicroSims — small, interactive simulations designed to visualize how code affects hardware behavior.

With this toolchain installed, you're ready to start building and debugging embedded systems with confidence.

Section 4: Embedded vs General-Purpose Programming¶

Programming a microcontroller is very different from writing software for a desktop or smartphone.

While general-purpose computers focus on speed, user interaction, and multitasking, embedded systems are designed for deterministic control of hardware — often under tight resource constraints.

General-Purpose Programming (e.g., Python, Java)¶

Focus on user experience and abstraction
Often use operating systems for multitasking and memory management
Can be inefficient — memory and CPU are plentiful

Embedded Programming (e.g., C, Assembly)¶

Runs bare-metal or with minimal OS support
Must manage timing, memory, and power directly
Designed for real-world interaction: controlling motors, reading sensors, etc.
Emphasis on efficiency and predictability

Concept	Embedded Systems	General-Purpose Systems
Environment	Real-time, resource-constrained	OS-managed, multi-user
Timing	Deterministic, cycle-aware	Flexible, best-effort
Language	C / Assembly	Java, Python, C#
Use Cases	Thermostats, robots, sensors	Web apps, spreadsheets, games

In embedded systems, a missed deadline or unexpected delay can cause system failure — timing is everything.

Throughout this textbook, we’ll write tight, predictable C and assembly code that gives us precise control over the hardware.

Section 5: Configuring Digital I/O Pins on the PIC24¶

Before using a microcontroller pin as a digital output, it must be correctly configured.
On the PIC24, three important registers control this:

Register	Purpose
TRISx	Sets the pin direction: 1 = Input, 0 = Output
LATx	Holds the output value for the pin: 1 = High, 0 = Low
AD1PCFG	Selects digital or analog mode: 1 = Digital, 0 = Analog

🔹 Typical Setup for Digital Output:¶

Configure TRISx bit to 0 → set pin as output
Set AD1PCFG bit to 1 → disable analog input (ensure digital function)
Control LATx bit → drive output high or low

If any step is missed, the pin might behave unexpectedly (e.g., float, stay analog, or refuse to drive an output).

Interactive MicroSim: Digital Output Pin Configurator¶

To better understand how PIC24 pins are configured for digital output, interact with the MicroSim below.

👉 Launch the Pin Configuration Simulation

Experiment with the TRIS, AD1PCFG, and LAT settings to see how they affect the final pin state.

Section 6: Summary and Use Cases¶

Let’s review the key points from this chapter:

Core Ideas¶

A microcontroller is a self-contained system with a CPU, memory, and peripherals built into one chip
The PIC24FJ64GA002 is a 16-bit MCU with timers, ADCs, communication modules, and 64 KB of Flash
Development is done using MPLAB X IDE and the XC16 compiler
Embedded programming focuses on predictability, efficiency, and hardware interaction

Where Are Microcontrollers Used?¶

Use Case	Example Devices
Consumer Electronics	Thermostats, smart watches, toys
Automotive	Airbags, ABS controllers, key fobs
Industrial Automation	Motor drivers, temperature sensors
Medical Devices	Heart monitors, insulin pumps
Robotics & Prototyping	Line-following robots, drones

As you go through this book, you’ll develop the low-level control skills that make these devices possible — starting from the very first line of assembly code.

Quiz: Microcontroller Fundamentals¶

Which of the following is true about microcontrollers?

They require an operating system to function
They are mainly used for high-performance graphics
They integrate a CPU, memory, and peripherals on one chip
They must be connected to the internet to work

Show Answer

The correct answer is C.

Microcontrollers are self-contained systems with a CPU, RAM, Flash, and I/O peripherals — all integrated onto one chip.
They are designed for dedicated, low-power control tasks, not general-purpose computing.

Prompt Practice¶

Think of an everyday device that uses a microcontroller (e.g., microwave, car key fob, thermostat).
How might that microcontroller interact with the real world?

Write a short description answering the following:

What is the microcontroller sensing?
What outputs or devices does it control?
Why is a microcontroller useful in this case?

Click to show example

Smart Thermostat

Senses room temperature using a digital temperature sensor
Controls the HVAC system by turning heating/cooling on or off
Microcontroller use: Performs decisions based on user input and sensor data. Communicates with Wi-Fi to support remote control.