Project 17: Teensy Instrument Platform - Modular Sensor and USB Studio

Integrate sensors, DMA streaming, USB identities, and logging into a robust instrument platform.

Quick Reference

Attribute Value
Difficulty Level 4: Expert
Time Estimate 40-80 hours
Main Programming Language C++
Alternative Programming Languages C
Coolness Level Level 5: Pure Magic
Business Potential 4. The “Open Core” Infrastructure
Prerequisites C/C++ basics, Teensyduino setup, basic electronics, ability to use a multimeter/logic analyzer
Key Topics system integration, data pipelines, fault handling

1. Learning Objectives

By completing this project, you will:

  1. Explain the core question for this project in your own words.
  2. Implement the main workflow and validate it with measurements.
  3. Handle at least two failure modes and document recovery.
  4. Produce a deterministic report that matches hardware behavior.

2. All Theory Needed (Per-Concept Breakdown)

System Integration: Data, Control, and Power Paths

Fundamentals An embedded system is a coordination of data flow, control flow, and power flow. Integration means sensors, DMA, USB, storage, and fault handling work together without violating timing or power limits. A modular architecture with clear interfaces makes integration measurable and repeatable.

Deep Dive into the concept Integration starts with architecture. Data path: sensors -> DMA -> processing -> USB/SD. Control path: interrupts, scheduling, state machines. Power path: regulators, brownout detection, watchdog. Interactions between these paths cause real bugs: DMA can increase latency, SD writes can block processing, USB disconnects can backpressure buffers. The integration process is incremental. Add one subsystem at a time, measure system metrics (CPU load, buffer occupancy, error counts, power draw), and compare to baseline. Fault handling is part of integration: detect errors, log them, and recover or enter safe mode. This project builds a full instrument platform and proves it with deterministic demos.

How this fit on projects This concept directly powers the implementation choices and validation steps in this project.

Definitions & key terms

  • Data path: Flow of sensor data through the system.
  • Control path: Scheduling and state transitions governing behavior.
  • Power path: How power is supplied, monitored, and managed.
  • Integration test: Test that validates multiple subsystems together.

Mental model diagram (ASCII)

Sensors -> DMA -> Processing -> USB/SD | Control -> Scheduler | Power -> Watchdog

How it works (step-by-step)

  1. Define modules and interfaces for each subsystem.
  2. Integrate one subsystem at a time and measure impact.
  3. Add telemetry counters for buffers, errors, and latency.
  4. Implement fault recovery and safe mode.

Minimal concrete example

STATUS: bufA=12% bufB=0% usb=OK sd=OK isr=4us

Common misconceptions

  • If each subsystem works, the system will work.
  • Integration bugs are random hardware issues.
  • Logging errors is enough without recovery.

Check-your-understanding questions

  • How do you detect integration regressions?
  • What is a good baseline metric set?
  • How do you prioritize fault recovery?

Check-your-understanding answers

  • Compare system metrics before and after integration changes.
  • CPU load, buffer occupancy, error counters, power draw.
  • Recover critical data paths first, then non-critical features.

Real-world applications

  • Test instrumentation
  • Industrial monitoring
  • Embedded audio systems

Where you’ll apply it

References

  • Systems engineering texts
  • PJRC Teensy integration examples

Key insights

Integration succeeds when data, control, and power constraints are measured together.

Summary

A reliable system is built by incremental integration with metrics and recovery.

Homework/Exercises to practice the concept

  • Define three metrics that detect integration regressions.
  • Simulate a subsystem failure and verify safe mode.

Solutions to the homework/exercises

  • Track buffer occupancy, error counts, and power draw over time.
  • Disable a sensor in software and confirm fallback behavior.

3. Project Specification

3.1 What You Will Build

Integrate sensors, DMA streaming, USB identities, and logging into a robust instrument platform.

3.2 Functional Requirements

  1. Integrate at least two sensors with DMA capture.
  2. Stream data over USB (HID/MIDI/Serial).
  3. Log data to SD with recovery logic.
  4. Implement fault handling and safe mode.

3.3 Non-Functional Requirements

  • Performance: Meet the target timing/throughput for the project.
  • Reliability: Detect errors and recover without undefined behavior.
  • Usability: Provide clear logs and a repeatable workflow.

3.4 Example Usage / Output

./P17-teensy-instrument-platform --run

3.5 Data Formats / Schemas / Protocols

Unified record format with headers, timestamps, and checksums

3.6 Edge Cases

  • USB disconnect mid-stream
  • SD card removed during logging
  • Sensor failure or timeout

3.7 Real World Outcome

You will run the project and see deterministic logs and measurements that match physical hardware behavior.

3.7.1 How to Run (Copy/Paste)

cd project-root
make
./P17-teensy-instrument-platform --run

3.7.2 Golden Path Demo (Deterministic)

Use a fixed input configuration and a known test signal. Capture output for 60 seconds and verify it matches expected values.

3.7.3 If CLI: exact terminal transcript

$ ./P17-teensy-instrument-platform --run --seed 42
[INFO] Teensy Instrument Platform - Modular Sensor and USB Studio starting
[INFO] Report saved to data/report.csv
[INFO] Status: OK
$ echo $?
0

Failure Demo (Deterministic)

$ ./P17-teensy-instrument-platform --run --missing-device
[ERROR] Device not detected
$ echo $?
2

4. Solution Architecture

4.1 High-Level Design

Inputs -> Acquisition -> Processing -> Output/Log

4.2 Key Components

Component Responsibility Key Decisions
Acquisition Configure peripherals and capture data Use stable clock settings
Processing Convert raw data to meaningful values Apply calibration/filters
Output/Log Emit reports and logs CSV for reproducibility

4.3 Data Structures (No Full Code)

struct Sample {
    uint32_t timestamp_us;
    uint32_t value;
    uint32_t flags;
};

4.4 Algorithm Overview

Key Algorithm: Measurement + Report

  1. Initialize hardware and verify configuration.
  2. Capture data and record timestamps.
  3. Compute metrics and write report.

Complexity Analysis:

  • Time: O(n) in samples
  • Space: O(n) for log storage

5. Implementation Guide

5.1 Development Environment Setup

# Arduino IDE + Teensyduino must be installed
# Optional CLI workflow
arduino-cli core update-index
arduino-cli core install teensy:avr

5.2 Project Structure

project-root/
├── src/
│   ├── main.ino
│   ├── hw_config.h
│   └── measurements.cpp
├── tools/
│   └── analyze.py
├── data/
│   └── samples.csv
└── README.md

5.3 The Core Question You’re Answering

“How do I build a full embedded instrument that survives real-world faults?”

5.4 Concepts You Must Understand First

Stop and research these before coding:

  1. system integration, data pipelines, fault handling
  2. Data logging and measurement techniques
  3. Basic timing math and error analysis

5.5 Questions to Guide Your Design

  1. What is the system’s data rate and latency target?
  2. Which subsystems are critical?
  3. How will you recover from logging failure?

5.6 Thinking Exercise

Draw the data/control/power path and mark bottlenecks.

5.7 The Interview Questions They’ll Ask

  1. How do you integrate DMA, USB, and logging safely?
  2. What metrics prove system stability?
  3. How do you design for fault recovery?

5.8 Hints in Layers

  • Integrate one subsystem at a time.
  • Add metrics for buffer occupancy and error counts.
  • Test failure paths deliberately.

5.9 Books That Will Help

| Topic | Book | Chapter | |——-|——|———| | Systems design | Making Embedded Systems | All | | Reliability | Designing Embedded Systems | Ch. 9 | | Architecture | Embedded Systems Architecture | Ch. 1-3 |

5.10 Implementation Phases

Phase 1: Foundation (10 hours)

Goals:

  • Integrate sensors
  • Build base pipeline

Tasks:

  1. Integrate sensors
  2. Build base pipeline

Checkpoint: Data path works

Phase 2: Core Functionality (20 hours)

Goals:

  • USB streaming
  • SD logging

Tasks:

  1. USB streaming
  2. SD logging

Checkpoint: System stable

Phase 3: Polish (10 hours)

Goals:

  • Fault recovery
  • Final demo

Tasks:

  1. Fault recovery
  2. Final demo

Checkpoint: Capstone ready

5.11 Key Implementation Decisions

| Decision | Options | Recommendation | Rationale | |———-|———|—————-|———–| | Buffering | Single buffer, double buffer | Double buffer | Avoids data loss during processing | | Logging format | CSV, binary | CSV | Human-readable while still scriptable | | Clock speed | Default, overclock | Default | Keeps peripherals in spec |

6. Testing Strategy

6.1 Test Categories

| Category | Purpose | Examples | |———-|———|———-| | Unit Tests | Validate math, parsing, and conversions | Timer math, CRC checks | | Integration Tests | Verify peripherals and pipelines | DMA -> buffer -> log | | Edge Case Tests | Handle boundary conditions | Brownout, missing sensor |

6.2 Critical Test Cases

{test_cases}

6.3 Test Data

Use a fixed test input pattern and record outputs to data/report.csv

7. Common Pitfalls & Debugging

7.1 Frequent Mistakes

| Pitfall | Symptom | Solution | |———|———|———-| {pitfalls}

7.2 Debugging Strategies

{debug_strats}

7.3 Performance Traps

Large buffers improve stability but increase latency. Measure both throughput and jitter to choose the right size.

8. Extensions & Challenges

8.1 Beginner Extensions

{ex_begin}

8.2 Intermediate Extensions

{ex_inter}

8.3 Advanced Extensions

{ex_adv}

9. Real-World Connections

9.1 Industry Applications

{industry_apps}

{open_source}

9.3 Interview Relevance

{interview_rel}

10. Resources

10.1 Essential Reading

{resources}

10.2 Video Resources

  • Embedded systems timing walkthrough (YouTube)
  • Teensy hardware deep dive (Conference talk)

10.3 Tools & Documentation

  • Teensyduino: Toolchain for Teensy boards
  • Logic Analyzer: Timing verification
  • Multimeter: Voltage and current measurement

{related_projects}

11. Self-Assessment Checklist

11.1 Understanding

  • I can explain the main concept without notes.
  • I can explain why the measurements match (or do not match) expectations.
  • I understand at least one tradeoff made in this project.

11.2 Implementation

  • All functional requirements are met.
  • All critical test cases pass.
  • Logs and reports are reproducible.
  • Edge cases are handled.

11.3 Growth

  • I documented lessons learned.
  • I can explain this project in a job interview.
  • I identified one improvement for next iteration.

12. Submission / Completion Criteria

Minimum Viable Completion: {comp_min}

Full Completion: {comp_full}

Excellence (Going Above & Beyond): {comp_ex}