Basic GPIO Expander – MCP23017

A simpler, budget-friendly 16-channel GPIO expander based on the MCP23017. Perfect for hobbyists, prototyping, and educational projects. Chain up to 8 modules for 128 GPIOs controlled via I²C.

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✨ Features

• 🧠 MCP23017 – 16-bit I²C I/O expander
• 🔌 I²C Interface – Up to 8 devices on same bus (128 GPIO)
• 🔢 Binary Address Selection – 3 jumpers + 3 LEDs show address (0-7)
• 💡 Status LEDs – For each I/O channel (via testing board)
• 🔋 Flexible Power – 5V/24V selectable via jumper
• 🏗️ Compact Size – 100×40mm, fits JLCPCB $2 special offer
• 🔍 Reverse Polarity Protection – MB2S bridge rectifier
• 💰 Budget-Friendly – 15 fewer components than industrial version

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📁 Repository Contents

Folder	Description
📂 /GERBER	Ready-to-order Gerber files
📄 /Schematic	PDF + image exports
🖥️ /PCB_Layout	PCB views (top/bottom/layers)
📸 /Images	Real build photos + 3D renders
📁 /Software	Arduino test code

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🛒 How to Order

1. Upload Gerber files to JLCPCB
2. Select: FR-4 material / 1.6mm thickness / ENIG surface finish
3. PCB Specifications:
   • Layers: 2
   • Size: 100mm × 40mm → Eligible for $2 special offer!
   • Color: Purple (or any color you like)
4. Add stencil if you plan to assemble yourself

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🔧 How to Assemble

SMD Assembly (Hot Plate / Reflow):

1. Apply solder paste through stencil
2. Place components (start with smallest first)
3. Reflow on hot plate (245°C peak)
4. Inspect under microscope for bridges

Through-Hole Assembly:

1. Insert terminal blocks, jack connector, and jumpers
2. Solder each pin with temperature-controlled iron
3. Trim excess leads
4. Clean with isopropyl alcohol

Assembly Order:

1. SMD Components (resistors/caps → ICs → LEDs)
2. Through-Hole Components (terminal blocks → connectors → jumpers)
3. Final Inspection and cleaning

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💻 How to Program

1️⃣ Set I²C Address

• Use 3 jumpers (A0, A1, A2)
• Jumper ON = Logic 0, Jumper OFF = Logic 1
• Address = (A0 × 1) + (A1 × 2) + (A2 × 4)
• Binary LEDs show the current address

2️⃣ Connect I²C

MCU → I2C_IN Connector (bottom left) VCC GND SDA SCL For chaining: I2C_OUT → Next Module's I2C_IN (bottom right → bottom left)

3️⃣ Upload Arduino Sketch

Check the Software folder for test code

⭐ Special Access

You can get direct access to this circuit files online through this link: Altium Online Access

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📺 Watch the Tutorial

🎥 Click here for the full YouTube video

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📜 License

This project is licensed under the MIT License – see the LICENSE file for details.

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🙌 Support

If you try this project, share your build!
⭐ Star this repo if you found it useful.

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About

🔍 A simpler, budget-friendly 16-channel GPIO expander based on the MCP23017. Perfect for hobbyists, prototyping, and educational projects. Chain up to 8 modules for 128 GPIOs controlled via I²C.

YouTube Tutorial Link

Topics

gpio-expander mcp23017 i2c arduino esp32 raspberry-pi open-hardware embedded-systems diy-electronics budget-electronics