STM32 CAN Relay Board Design

I need a straightforward yet reliable design for a small STM32-based board that will live inside an automotive environment. Its core tasks are simple control and communication duties, so the essentials are:

• STM32 MCU of your choice
• On-board CAN transceiver (no extra UART/SPI/I2C lines are required beyond what the MCU naturally exposes)
• Pins for programming the microcontroller are to be exposed
• One opto-isolated relay output rated for 230 V AC, 10 A
• Taking into account the fluctuating voltage in the automotive installation when powering the microcontroller

Keep the scope lean: I’m after a clean schematic, a compact 2-layer PCB layout, and ready-to-manufacture Gerber files with an accompanying BOM. A basic PDF of the schematic and PCB renders is enough for documentation at this stage.

Please follow common automotive design practices—proper decoupling, trace clearance for the mains relay, and clear test points for firmware flashing. If you’ve done similar STM32/CAN hardware before, this should be quick work.