Design & Prototype Nema 17 Closed-Loop Stepper Controller with Ir Interface

We are seeking an experienced freelancer to design and prototype a compact, low-cost, closed-loop stepper controller. This controller will be a PD Stepper derivative, designed to mount directly to the rear of a NEMA 17 motor. The system requires a wire-free 2-way IR interface and dual opto-isolated inputs for flexible homing or sensing applications. The project encompasses core hardware, power management, connectivity, mechanical design, and firmware development.

Core Hardware & Power:
- Microcontroller: Utilize an STM32U0 series (Ultra-low-power Cortex-M0+) with a 4-pin SWD header for debugging and programming.
- Motor Driver: Integrate a Trinamic TMC2209, configured via UART, with StallGuard4 connected via EXTI for low-latency stall detection.
- Position Feedback: Implement an AS5600 magnetic rotary encoder, precisely aligned for a diametric magnet on the motor shaft.
- Power Management: Design an integrated high-voltage buck converter capable of stepping down 28V to 3.3V at 500ma to power the mcu, ir transceiver, and sensor logic.

Connectivity & Isolation:
- Wire-Free Control: Develop a 2-way Infrared (ir) uart bridge, ideally using an mcp2120 + tfdu4101 or equivalent components, for industrial wire-free configuration and status monitoring.
- Isolated Inputs: Include two opto-isolated channels (e.g., PC817) to support homing sensors or limit switches.
- Voltage Support: The system must support 5V-24V field signals for sensor inputs.
- Versatility: Ensure input pins are routable to STM32 inputs, configurable as EXTI (Digital) or ADC (Analog) for compatibility with various specialized sensors.

Mechanical & Thermal Design:
- Form Factor: The pcb must adhere to a 42mm x 42mm footprint with 31mm bolt spacing, matching the nema 17 motor standard.
- Thermal Management: Incorporate large thermal pads under the TMC2209 and include two dedicated M3 mounting holes to accommodate a custom heatsink or water block.
- Field Wiring: Provide industrial-grade screw terminals or spring-clamp connectors for power, motor coils, and sensor inputs.

Firmware & Deliverables:
- Firmware: Develop the firmware in C/C++ using Stm32cubeide, featuring robust closed-loop pid control, accurate stall detection, and an ir-based command api for external interaction.
- Design Files: Deliver a complete KiCad project, including a Bill of Materials (bom) compatible with jlcpcb and gerber files for manufacturing.
- Testing: Provide a demonstrated prototype showcasing closed-loop accuracy, reliable IR communication, and successful sensor-triggered homing functionality.