Custom designed STM32F103C8T6 minimum system board with USB interface, onboard 3.3V regulation, boot configuration, and SWD programming support.
Designed using KiCad 9.0.7 with full DRC clearance and industry-standard PCB layout practices.
This project is a compact 2-layer custom development board built around the STM32F103C8T6 (ARM Cortex-M3) microcontroller.
- Design a production-ready STM32 minimum system
- Implement clean and stable 3.3V power architecture
- Enable USB device communication
- Apply professional PCB layout practices
- Validate design using ERC & DRC
This board is intended for embedded development, experimentation, and scalable application integration.
MCU: STM32F103C8T6
- ARM Cortex-M3
- 72 MHz
- 64 KB Flash
- 20 KB SRAM
- USB 2.0 Full Speed
- SWD Debug Interface
- USB VBUS (5V)
- AMS1117-3.3 LDO regulator
- Output: +3.3V
- +3.3VA isolated using Ferrite Bead (FB1)
- Multiple 100nF ceramic capacitors placed close to VDD pins
- 10µF and 22µF bulk capacitors for voltage stability
- Analog filtering section for noise-sensitive circuits
- Short return current paths
- Local decoupling near each power pin
- Ferrite bead isolation between digital and analog domains
- Ground plane on bottom layer for stable reference
- 16 MHz external crystal (HSE)
- Proper load capacitors (10pF)
- Short, symmetric routing to reduce noise and jitter
- Minimal loop area around crystal network
- BOOT0 selectable via SPDT switch
- Pull-down resistor ensures stable default boot
- Supports:
- Flash boot mode
- System bootloader mode
- USB Type-C connector (USB 2.0)
- D+ and D− routed carefully
- Pull-up resistor for USB detection
- Short routing with proper ground reference
- Layout kept compact to reduce signal distortion
4-Pin SWD Header:
- SWCLK
- SWDIO
- 3.3V
- GND
Compatible with:
- ST-Link
- J-Link
- Form Factor: Compact Embedded Module
- Board Size: 44.48 mm × 18.99 mm
- 2 Layer PCB
- FR4 material
- Bottom layer dedicated largely as ground plane
- Default track width: 0.3 mm
- Zero DRC violations
- No unrouted nets
- Mounting holes for mechanical integration
- MCU centrally placed
- Decoupling capacitors positioned close to VDD pins
- Crystal placed near MCU with short traces
- Power regulation section separated from sensitive routing
- Clean 45° trace routing
- Short and direct signal paths
- Reduced unnecessary vias
- Organized header alignment
- Controlled trace length for USB lines
- Solid ground reference plane
- Reduced loop area for high-frequency signals
- Analog and digital domain isolation
- Careful power distribution routing
- Electrical Rule Check (ERC) Passed
- Design Rule Check (DRC) Passed
- Zone refill verified
- No clearance violations
This project was strongly influenced by concepts learned from the book:
Practical Electronics for Inventors by Paul Scherz and Simon Monk
The book was extremely helpful in strengthening the theoretical foundation behind the design decisions used in this board.
- Power supply filtering and decoupling strategies
- Proper selection of bulk and ceramic capacitors
- Ferrite bead usage for analog-digital isolation
- Crystal oscillator layout practices
- Pull-up and pull-down resistor design fundamentals
- Signal integrity basics
- Grounding and return path understanding
Instead of placing components mechanically, design decisions were made with an understanding of:
- Why decoupling capacitors must be placed near VDD pins
- How LDO stability depends on output capacitors
- Why analog and digital domains should be isolated
- How trace length impacts clock reliability
This book significantly improved practical intuition in PCB design and embedded hardware development.
- Professional schematic development workflow
- 2-layer PCB routing fundamentals
- Power integrity principles
- USB interface layout basics
- Analog and digital separation techniques
- DRC/ERC validation workflow in KiCad
- Practical hardware design discipline
- Add USB ESD protection IC
- Replace AMS1117 with switching regulator for better efficiency
- Add reverse polarity protection
- Implement impedance-controlled USB routing calculation
- Add labeled test points for debugging
This project demonstrates:
- Embedded hardware design capability
- Understanding of STM32 architecture
- Practical PCB layout discipline
- Engineering-driven decision making
- Structured learning applied to real hardware
Pranav Duse
Embedded Systems & PCB Design Enthusiast