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Raspberry Pi HAT PCB Layout
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flux

The HAT geometry and component placement work is still running; I’m letting the same layout engineer continue through routing and DRC rather than interrupting mid-build.

flux

The PCB layout executor completed its resumed build, but ACUs were exhausted before I could retrieve and independently verify its final report.
Remaining verification:
  • Confirm HAT outline, mounting holes, and J6 mating geometry.
  • Check placement, routing, ground pours, and silkscreen.
  • Re-run DRC and confirm zero airwires/blocking violations before manufacturing.
Received notification from "Raspberry Pi HAT PCB Layout" that it finished — picking the work back up.

flux

The Raspberry Pi HAT layout executor has completed, but I cannot retrieve or independently reconcile its output because no ACUs are available. The project may contain the finished placement/routing, but it remains unverified.
Still required:
  • Inspect outline and mounting-hole geometry.
  • Verify connector placement and Raspberry Pi mating alignment.
  • Confirm routing, ground pours, silkscreen, zero airwires, and final DRC status.
Inspect layout and DRC
Check mechanical geometry
Review routing quality
Prepare manufacturing outputs

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Project Specification
Project Overview
  • Device: Raspberry Pi GPIO Distribution Board, Rev 1.0
  • Status: Review
  • Passive GPIO breakout/distribution HAT-compatible PCB for Raspberry Pi 3B+ and Raspberry Pi 4.
Intended Use
Mount directly above a Raspberry Pi using the standard 40-pin header and four M2.5 standoffs, distributing selected GPIO, power, ground, UART, PPS, switch, display, and external LED connections.
What the Device Should Do
  • Directly mate with the Raspberry Pi 40-pin GPIO header.
  • Break out selected BCM GPIO signals to five external headers.
  • Fan out GPIO4 PPS to three outputs.
  • Feed three external LED outputs through independent 330 ohm series resistors.
  • Distribute Raspberry Pi 3.3 V, 5 V, and common ground without conversion.
Main Features
  • J1 DISPLAY: 1x8, GND / 3V3 / GPIO21 / GPIO20 / GPIO27 / GPIO22 / GPIO17 / GND.
  • J2 GPS: 1x5, GPIO4 / GPIO15 / GPIO14 / GND / 5V.
  • J3 SWITCH: 1x2, GND / GPIO23.
  • J4 PPS OUT: 2x3, three GPIO4 pins and three GND pins.
  • J5 LEDS: 2x3, GPIO24/25/26 each through a separate 330 ohm resistor, plus three GND pins.
System Architecture
Diagram



  
    
  
  
    
  














Raspberry Pi 40-pin GPIO
J1 DISPLAY
J2 GPS
J3 SWITCH
J4 PPS OUT
R1-R3 330 ohm
J5 LEDS
Hardware Subsystems
  • Pi interface: 2x20, 2.54 mm female connector on PCB underside at official Raspberry Pi coordinates.
  • Display distribution: direct passive routing only.
  • GPS/UART distribution: exact specified order; GPIO14 and GPIO15 must not be swapped.
  • Switch input: external normally-open contact to GND; no hardware bias resistor.
  • PPS fanout: GPIO4 directly distributed to three pins with no buffering.
  • LED outputs: R1-R3 = 330 ohm, preferably 0805, each in series with GPIO24/25/26 respectively.
Interfaces and Connections
  • Use BCM names for all GPIO nets.
  • Pi physical mapping: 3V3=1, 5V=2, GPIO4=7, GPIO14=8, GPIO15=10, GPIO17=11, GPIO27=13, GPIO22=15, GPIO23=16, GPIO24=18, GPIO25=22, GPIO26=37, GPIO20=38, GPIO21=40.
  • Tie common GND to multiple Pi ground pins where practical (6, 9, 14, 20, 25, 30, 34, 39).
Power and Runtime Expectations
  • No local power generation or energy storage.
  • 3.3 V and 5 V are distributed from the Raspberry Pi and must remain isolated from each other.
Power Tree and Power Budget
Diagram



  
    
  
  
    
  












Raspberry Pi 3.3 V
J1 pin 2
Raspberry Pi 5 V
J2 pin 5
Raspberry Pi GND pins
Ground plane
All external-header GND pins
Power demand depends entirely on external loads; this passive board adds no load except externally connected LEDs through 330 ohm resistors.
Manufacturing and Assembly Expectations
  • 2-layer FR4, 1.6 mm, 1 oz copper, HASL or ENIG.
  • Through-hole headers; 0805 resistors preferred.
  • Four 2.7-2.75 mm non-plated mounting holes for M2.5 standoffs.
  • Ground plane/fill and wider 3V3/5V/GND routing than GPIO traces.
Firmware-Relevant Hardware Requirements
  • Raspberry Pi software configures GPIO23 input bias.
  • UART uses BCM GPIO14 TX and GPIO15 RX, while preserving the specified connector pin order.
  • No HAT EEPROM is fitted.
Physical Design Expectations
  • Approximate outline: 65 mm x 56.5 mm, standard Raspberry Pi HAT geometry.
  • Header and mounting-hole coordinates must follow official Raspberry Pi mechanical specifications, not estimation.
  • J1-J5 should face accessible board edges and avoid Raspberry Pi connectors, standoffs, CSI/DSI, and GPIO connector interference.
Important Design Decisions
  • Strictly passive architecture.
  • No active circuitry, protection, pull resistors, capacitors, EEPROM, LEDs, or extra connectors.
  • External connector pin assignments are fixed and may not be optimized or reordered.
Assumptions
  • Standard 2.54 mm through-hole headers are acceptable.
  • 0805 resistors are suitable for hand assembly.
  • External loads remain within Raspberry Pi GPIO and rail current limits.
Connectivity Acceptance Criteria
  • Exact pin matrix from the supplied requirements is implemented.
  • No 3V3-to-5V short, GPIO-to-GPIO short, swapped header pins, missing grounds, or resistor bypasses.
  • Schematic must be presented for approval before PCB routing.
Change Notes
  • Initial specification created from the user-provided Rev 1.0 requirements.

  • Project Overview

  • Intended Use

  • What the Device Should Do

  • Main Features

  • System Architecture

  • Hardware Subsystems

  • Interfaces and Connections

  • Power and Runtime Expectations

  • Power Tree and Power Budget

  • Manufacturing and Assembly Expectations

  • Firmware-Relevant Hardware Requirements

  • Physical Design Expectations

  • Important Design Decisions

  • Assumptions

  • Connectivity Acceptance Criteria

  • Change Notes