Raspberry Pi HAT for IR Transmission

Project Overview Custom Raspberry Pi HAT (compatible with 3B and 4B models) designed for high-density IR signal transmission and learning. The board acts as a centralized IR bridge, driven by custom Python/Flask software on the Pi. The Pi requires no additional I/O functions beyond this IR management. Hardware Specifications 1. Power Delivery Input: 1x USB-C receptacle on the HAT. Routing: The USB-C port must power the HAT's circuitry and back-power the Raspberry Pi specifically via the 4 pins located near the main GPIO header (the PoE header pins). 2. IR Input (Learning) Component: 1x onboard IR receiver module (e.g., TSOP38238 or equivalent 38kHz receiver). Routing: Connected to 1 GPIO pin for signal learning. 3. IR Outputs (Transmission) Quantity: 20 independent channels. (The Raspberry Pi has 26 usable general-purpose GPIO pins. Dedicating 1 to the input leaves 25. Limiting to 20 ensures direct GPIO control is fully supported without the need for an expander IC). Connectors: 20x 3.5mm female audio jacks (Mono/TS) mounted to the board edges for connecting ready-made commercial IR emitters. Drivers: Each of the 20 channels must be driven by an independent transistor or MOSFET capable of handling the current draw of standard IR emitter LEDs. 4. Visual Feedback & Component Placement Indicators: 1x visible indicator LED per output channel. Circuitry: The visible LED must be placed in series (or parallel with an appropriate resistor) with the 3.5mm jack so that it only lights up when an emitter is connected and a signal is actively being sent. Placement Constraint: All visible indicator LEDs must be placed on the top side of the HAT (the side facing away from the Raspberry Pi). They must be positioned in a clear area to ensure full visibility when the HAT is mounted to the Pi.