Enviro

ENVIRO STM32F103 Development Board — Rev B

A 50 × 44 mm, four-layer STM32F103C8T6 development board revised as a portfolio-ready KiCad project. The board is USB-powered and provides SWD, USART1, I2C2, reset, BOOT0 selection, ESD protection, test points, and four M2 mounting holes.

Design highlights

• STM32F103C8T6 with 16 MHz HSE clock provision
• USB Micro-B power and USB full-speed interface with USBLC6-2SC6 protection
• TLV1117LV33 3.3 V regulator, 250 mA resettable fuse, decoupling, and a 3.3 V status LED
• Four-layer proposed stackup: top signal, solid internal ground, internal 3.3 V, bottom signal/ground
• 5-pin SWD: VTREF, SWDIO, SWCLK, GND, NRST
• USART1 header for the STM32 system-memory serial bootloader; I2C2 header on PB10/PB11

Usage

Open enviro.kicad_pro in KiCad 9. The included models/ directory provides the bundled KiCad 3D models used by the board. The USB connector model is not included because an official matching STEP model was not available from the library; this does not affect the PCB footprint or manufacturing data.

First bring-up plan

1. Inspect the bare board and verify no shorts between VBUS, 3.3 V, and GND.
2. Apply USB power and verify the 3.3 V rail at TP2.
3. Program through SWD, using pin 5 for reset if needed.
4. For ROM UART boot: set BOOT0 high, reset, and use USART1 (PA9 TX / PA10 RX); return BOOT0 low for normal flash boot.
5. Verify clock startup, USB enumeration, I2C, and reset on the physical prototype.

Important review items before ordering

• Confirm the chosen 16 MHz crystal's load capacitance and select C10/C11 to match its datasheet.
• Confirm the fabricator can provide the proposed 1.6 mm four-layer stackup. USB routing was kept short over the ground plane, but its impedance has not been fabricated or certified.
• The 3.3 V header pins are outputs / reference voltage, not an external power input.
• Perform thermal, USB, clock, and firmware bring-up testing on a physical board before claiming production readiness.