Audio Looper Schematic Design

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Please clear stuck auto-layout job auto-layout-9ba3e37e-54a0-4440-a55b-88d2a3abe751 on project chrubble/teensy-4-track-audio-looper. The UI shows no active job, but auto-route still fails because this job is active with status outOfCredit.
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auto-layout-9ba3e37e-54a0-4440-a55b-88d2a3abe751
Project: chrubble/teensy-4-track-audio-looper
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Project Specification
Project Overview
Status: Draft schematic design. Compact POKI-inspired 4-track audio looper based on Teensy 4.1 and PJRC Teensy Audio Shield Rev D/D2.
Intended Use
Small desktop instrument/prototype for firmware-controlled mono 4-track looping v1, while retaining stereo hardware line input/output for future stereo looping.
What the Device Should Do
  • Capture stereo line input through SGTL5000 codec.
  • Store loops on microSD via the Audio Shield.
  • Provide 4 track level controls, track buttons, global buttons, encoder, and LED feedback.
  • Run from Teensy USB 5 V during prototype use.
Main Features
  • Teensy 4.1 MCU.
  • Teensy Audio Shield Rev D/D2 with SGTL5000 codec and microSD.
  • Stereo panel-mount 3.5 mm TRS line input and line output.
  • 4 track level pots plus optional master pot.
  • 17 push buttons total plus rotary encoder with push switch.
  • 11 status LEDs.
  • GPIO expansion/LED shift-register support where needed.
System Architecture
Diagram



  
    
  
  
    
  
























USB node_5V into Teensy
Teensy 4.1
Teensy Audio Shield Rev D or D2
Stereo Line In Jack
Stereo Line Out Jack
microSD
Pots
Buttons
MCP23017 I2C GPIO Expander
74HC595 LED Shift Register
11 LEDs
Rotary Encoder
Hardware Subsystems
  • Core compute/audio: Teensy 4.1 and PJRC Audio Shield using I2S, I2C, and SPI interconnects.
  • Controls: analog pots to Teensy ADC pins; buttons via I2C GPIO expander; encoder direct to Teensy GPIO.
  • Indication: LEDs driven through 74HC595 serial-in/parallel-out shift registers and current limiting resistors.
  • Power: USB 5 V input through Teensy; 3.3 V distributed to logic/control circuitry; local and bulk decoupling.
  • Audio I/O: shield line-in/line-out routed to TRS panel jacks; codec headphone VGND is not system ground.
Interfaces and Connections
  • I2S: MCLK, BCLK, LRCLK, DIN, DOUT between Teensy and Audio Shield.
  • I2C: SDA/SCL shared by SGTL5000 and MCP23017.
  • SPI: CS, MOSI, MISO, SCK for microSD on Audio Shield.
  • Off-board: line-in jack, line-out jack, pots, buttons, LEDs, encoder.
Power and Runtime Expectations
Prototype powered from USB via Teensy 5 V. No battery runtime target specified.
Power Tree and Power Budget

Table

RailLoadsEstimated Current
5 V USBTeensy VIN and onboard regulationTBD from module datasheets
3.3 VTeensy logic, Audio Shield, MCP23017, 74HC595, pots, LEDsTBD; design target below Teensy 3.3 V regulator capability unless external 3.3 V is added
Manufacturing and Assembly Expectations
Prototype schematic. Default to SMD passives for compact board unless hand-soldering is requested later. Use clearly labeled connectors for off-board panel wiring.
Firmware-Relevant Hardware Requirements
Firmware must initialize SGTL5000 over I2C, configure I2S audio streaming, access microSD over SPI, scan MCP23017 buttons, read ADC pots, read encoder, and update LED shift registers.
Physical Design Expectations
Keep audio jack-to-codec routes short and separated from LED/button wiring. Use one common ground; do not tie headphone VGND to system ground.
Important Design Decisions
  • Use MCP23017 for buttons to save Teensy GPIO.
  • Use two 74HC595 devices for 11 LEDs to save GPIO.
  • Keep stereo audio hardware for future expansion.
Assumptions
  • Teensy 4.1 and Audio Shield are represented as module/header parts if exact Flux library parts are available; otherwise equivalent connectors will be used.
  • Prototype power is USB only, with optional future DC jack header/protection placeholder.
Change Notes
  • Initial specification derived from attached Looper Schematic Design document.

    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

    Change Notes

Documents

    Project Specification

    Board Bring-Up Plan — Teensy 4-Track Audio Looper

    Firmware Starter — Teensy 4.1 Audio Looper

Assets

No assets added.

Teensy 4-Track Audio Looper

Teensy 4-Track Audio Looper thumbnail
Compact Teensy 4.1-based 4-track audio looper with SGTL5000 audio shield, stereo line I/O, microSD storage, pots, buttons, LEDs, and rotary encoder control surface.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$13.88–$19.65

Digi-Key

$55.84

HQonline

$2.47

LCSC

$26.07

Mouser

$67.74

TME

$1.00

Verical

$65.36–$104.24

Controls