Lesson 5: I2C Communication - Microcontroller Talking to Sensors

📌 Learning Objectives

1. Understand what I2C protocol is
2. Learn about I2C hardware connections
3. Learn to enable I2C sensors
4. Read temperature sensor data

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🎯 What is I2C?

I2C (pronounced I-squared-C) = Inter-Integrated Circuit

A Useful Analogy

Imagine a bus route with many stops:

• Bus = The shared communication lines
• Devices = The various stops
• Address = Each stop's unique number

All devices share two wires, distinguished by their addresses!

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🔌 I2C Hardware Connections

Only 2 wires needed + power and ground:

Wire Name	Function
SCL	Clock line
SDA	Data line
VCC	Power (3.3V or 5V)
GND	Ground

Connection Diagram

Microcontroller   Temperature Sensor   OLED Screen
       │                 │                 │
       ├─ SCL ──────────┼─ SCL ───────────┤
       ├─ SDA ──────────┼─ SDA ───────────┤
       ├─ VCC ──────────┼─ VCC ───────────┤
       └─ GND ──────────┴─ GND ───────────┘

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📮 How I2C Works

1. Each Device Has an Address

Sensor	I2C Address
BMP280	0x76
ADS1115	0x48
TCS34725	0x29
OLED	0x3C

2. Communication Process

1. Microcontroller sends address
2. Corresponding device responds
3. Send or receive data
4. End communication

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🔧 I2C Instructions in JoyKit

Instruction	Function
0xC0	Enable peripheral
0xC3	Enable temperature/humidity sensor (BMP280/BME280)
0xC7	Enable WS2812B

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🔬 Classroom Demo Project: Temperature Monitoring

Project Goal

Read and display temperature sensor data.

Hardware Requirements

• Onboard BMP280/BME280 sensor
• Screen (optional)

Reference Program

; Temperature monitoring project
000 C3 0001 0000  ; Enable temperature/humidity sensor
001 02 03E8 0000  ; Wait for sensor to stabilize
002 0E 0000 0000  ; loop (data automatically displayed on screen)

Advanced: Control LED with Temperature

; Change LED color based on temperature
000 C3 0001 0000  ; Enable sensor
001 C7 0001 0000  ; Enable LED
002 02 03E8 0000  ; delay
003 06 000A 001E  ; If temperature > 30°C, jump
004 E4 00FF 0000  ; Green (normal)
005 0E 0002 0000  ; jump back
006 E4 0000 00FF  ; Red (too hot warning)
007 0E 0002 0000  ; jump back

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💡 Advantages of I2C

Feature	Description
Wire efficient	Only needs 2 wires
Multiple devices	Can connect multiple sensors at once
Simple	Protocol is relatively simple

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🎯 Comparison with SPI

I2C	SPI
2 wires	4 wires
Has addresses	No addresses, uses chip select
Slower	Faster
Half-duplex	Full-duplex

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🎉 Summary

What we learned today:

• ✅ I2C is a bus protocol
• ✅ Requires SCL and SDA lines
• ✅ Each device has an address
• ✅ JoyKit uses 0xC0 series instructions to enable sensors
• ✅ Completed temperature monitoring project

Next lesson, we'll learn about SPI Protocol, then move to comprehensive projects!