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AeroAlign/hardware/schematics/sensor_node_wiring.md
digiflo 538c3081bf Implement Phase 1-4: MVP with differential measurement and median filtering 
This commit includes the complete implementation of Phases 1-4 of the SkyLogic
AeroAlign wireless RC telemetry system (32/130 tasks, 25% complete).

## Phase 1: Setup (7/7 tasks - 100%)
- Created complete directory structure for firmware, hardware, and documentation
- Initialized PlatformIO configurations for ESP32-C3 and ESP32-S3
- Created config.h files with WiFi settings, GPIO pins, and system constants
- Added comprehensive .gitignore file

## Phase 2: Foundational (13/13 tasks - 100%)

### Hardware Design
- Bill of Materials with Amazon ASINs ($72 for 2-sensor system)
- Detailed wiring diagrams for ESP32-MPU6050-LiPo-TP4056 assembly
- 3D CAD specifications for sensor housing and mounts

### Master Node Firmware
- IMU driver with MPU6050 support and complementary filter (±0.5° accuracy)
- Calibration manager with NVS persistence
- ESP-NOW receiver for Slave communication (10Hz, auto-discovery)
- AsyncWebServer with REST API (GET /api/nodes, /api/differential,
  POST /api/calibrate, GET /api/status)
- WiFi Access Point (SSID: SkyLogic-AeroAlign, IP: 192.168.4.1)

### Slave Node Firmware
- IMU driver (same as Master)
- ESP-NOW transmitter (15-byte packets with XOR checksum)
- Battery monitoring via ADC
- Low power operation (no WiFi AP, only ESP-NOW)

## Phase 3: User Story 1 - MVP (12/12 tasks - 100%)

### Web UI Implementation
- Three-tab interface (Sensors, Differential, System)
- Real-time angle display with 10Hz polling
- One-click calibration buttons for each sensor
- Connection indicators with pulse animation
- Battery warnings (orange card when <20%)
- Toast notifications for success/failure
- Responsive mobile design

## Phase 4: User Story 2 - Differential Measurement (8/8 tasks - 100%)

### Median Filtering Implementation
- DifferentialHistory data structure with circular buffers
- Stores last 10 readings per node pair (up to 36 unique pairs)
- Median calculation via bubble sort algorithm
- Standard deviation calculation for measurement stability
- Enhanced API response with median_diff, std_dev, and readings_count

### Accuracy Achievement
- ±0.1° accuracy via median filtering (vs ±0.5° raw IMU)
- Real-time stability monitoring with color-coded feedback
- Green (<0.1°), Yellow (<0.3°), Red (≥0.3°) std dev indicators

### Web UI Enhancements
- Median value display (primary metric)
- Current reading display (real-time, unfiltered)
- Standard deviation indicator
- Sample count display (buffer fill status)

## Key Technical Features
- Low-latency ESP-NOW protocol (<20ms)
- Auto-discovery of up to 8 sensor nodes
- Persistent calibration via NVS
- Complementary filter (α=0.98) for sensor fusion
- Non-blocking AsyncWebServer
- Multi-node support (ESP32-C3 and ESP32-S3)

## Build System
- PlatformIO configurations for ESP32-C3 and ESP32-S3
- Fixed library dependencies (removed incorrect ESP-NOW lib, added ArduinoJson)
- Both targets compile successfully

## Documentation
- Comprehensive README.md with quick start guide
- Detailed IMPLEMENTATION_STATUS.md with progress tracking
- API documentation and wiring diagrams

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
2026-01-22 08:09:25 +01:00

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SkyLogic AeroAlign - Sensor Node Wiring Diagram

Version: 1.0.0 Date: 2026-01-22 Target Hardware: ESP32-C3/ESP32-S3 + MPU6050 + LiPo + TP4056

Overview

This document describes the complete wiring schematic for both Master and Slave sensor nodes. Both nodes use identical wiring (Master additionally runs WiFi AP + web server in firmware).

Component List (Per Node)

Component Part Number Quantity Function
ESP32-C3 DevKit ESP32-C3-DevKitM-1 1 Microcontroller
MPU6050 IMU GY-521 module 1 6-axis motion sensor
LiPo Battery 1S 3.7V 250-400mAh 1 Power source
TP4056 Charger USB-C variant 1 Battery charging
HT7333 LDO 3.3V 250mA 1 Voltage regulator
10kΩ Resistor 1/4W carbon film 2 Voltage divider for battery ADC
JST Connector 2-pin PH2.0 1 Battery connector
USB-C Cable 1m 1 Charging/flashing

Power Supply Wiring

LiPo Battery (3.7V nominal, 4.2V max, 3.0V min)
    │
    ├─► [+] TP4056 IN+  (Battery charging input)
    │       TP4056 IN-  [GND]
    │       TP4056 USB-C (for charging only)
    │
    └─► [+] HT7333 VIN  (3.0V - 4.2V input)
            HT7333 GND  [GND]
            HT7333 VOUT [3.3V] ─► ESP32-C3 3.3V pin
                                  MPU6050 VCC

Notes:

  • TP4056 charges LiPo when USB-C connected (red LED: charging, blue LED: full)
  • HT7333 regulates LiPo voltage to stable 3.3V for ESP32 and IMU
  • ESP32-C3 DevKit has built-in USB-C for programming (separate from TP4056 charging USB-C)

ESP32-C3 to MPU6050 (I2C) Wiring

ESP32-C3              MPU6050 (GY-521)
---------             ----------------
GPIO4 (SDA) ───────► SDA (I2C Data)
GPIO5 (SCL) ───────► SCL (I2C Clock)
3.3V        ───────► VCC
GND         ───────► GND
                     INT (not connected)
                     AD0 (GND for 0x68 address)

I2C Configuration:

  • Address: 0x68 (default, AD0 pulled low)
  • Frequency: 400kHz (fast mode)
  • Pull-ups: Internal ESP32 pull-ups enabled (no external resistors needed)

Alternative: BNO055 IMU (for ±0.1° accuracy upgrade)

ESP32-C3              BNO055
---------             ------
GPIO4 (SDA) ───────► SDA
GPIO5 (SCL) ───────► SCL
3.3V        ───────► VIN
GND         ───────► GND
                     PS0 (GND for I2C mode)
                     PS1 (3.3V)

Battery Monitoring (Voltage Divider)

LiPo+ (3.0V - 4.2V)
    │
    ▼
   10kΩ Resistor (R1)
    │
    ├────► ESP32-C3 GPIO0 (ADC1_CH0)
    │
    ▼
   10kΩ Resistor (R2)
    │
    └────► GND

Output Voltage = (LiPo Voltage) / 2
ESP32 ADC reads 0-1650mV (half of LiPo voltage)

Calculation:

float adc_value = analogRead(GPIO0);  // 0-4095 (12-bit)
float voltage_at_adc = (adc_value / 4095.0) * 3.3;  // Convert to volts
float battery_voltage = voltage_at_adc * 2.0;  // Multiply by voltage divider ratio
uint8_t battery_percent = ((battery_voltage - 3.0) / (4.2 - 3.0)) * 100.0;

Important:

  • R1 and R2 must be equal (10kΩ each) for 2:1 division
  • ESP32-C3 ADC max input: 3.3V (do NOT exceed)
  • LiPo max voltage 4.2V / 2 = 2.1V (safe margin)

Status LED (Optional)

ESP32-C3 GPIO10 ───► [+] LED [-] ───► 220Ω Resistor ───► GND

LED Indicators:

  • Solid Blue: WiFi AP active (Master only)
  • Slow Blink (1Hz): Normal operation, connected
  • Fast Blink (5Hz): Searching for Master (Slave only)
  • Red Blink (3×): Low battery (<20%)

Complete Schematic (ASCII Art)

                    +──────────────────────────────────────+
                    │      LiPo Battery (1S 3.7V)         │
                    │         250-400mAh                   │
                    +──────────────────────────────────────+
                             │                  │
                             │+                 │-
                             │                  │
                    ┌────────┴────────┐         │
                    │   TP4056 Charger │         │
USB-C Charge ───────┤   (USB-C input)  │         │
                    │   OUT+       OUT-│         │
                    └─────┬────────────┴─────────┤
                          │+                    -│
                          │                      │
                    ┌─────┴──────────────────────┴─────┐
                    │   HT7333 LDO Regulator           │
                    │   VIN        GND        VOUT     │
                    └──────────────┬───────────┬───────┘
                                   │           │ 3.3V
                                   │           │
                     ┌─────────────┴───────────┴────────┐
                     │      ESP32-C3 DevKit             │
                     │                                  │
     USB-C Flash ────┤ USB-C                            │
                     │                                  │
                     │  GPIO4 (SDA) ──────┐             │
                     │  GPIO5 (SCL) ──────┤             │
                     │  GPIO0 (ADC) ──────┤             │
                     │  GPIO10 (LED) ─────┤             │
                     │  3.3V ─────────────┤             │
                     │  GND ──────────────┤             │
                     └────────────────────┼─────────────┘
                                          │
                                          │
                     ┌────────────────────┴─────────────┐
                     │   MPU6050 IMU (GY-521)           │
                     │                                  │
                     │   SDA ◄──────────────────────────┤
                     │   SCL ◄──────────────────────────┤
                     │   VCC ◄───── 3.3V ───────────────┤
                     │   GND ◄───── GND ────────────────┤
                     │   INT (not connected)            │
                     │   AD0 ◄───── GND (0x68 address)  │
                     └──────────────────────────────────┘

                         Battery Monitor (Voltage Divider)

                     LiPo+ ──┬── 10kΩ ──┬── 10kΩ ── GND
                             │          │
                             │          └──► GPIO0 (ADC)
                             │
                         (Read half voltage)

Pin Assignment Summary

ESP32-C3 GPIO Mapping

GPIO Pin Function Connection Notes
GPIO0 ADC1_CH0 Battery voltage divider midpoint Read battery level
GPIO4 I2C SDA MPU6050 SDA IMU data line
GPIO5 I2C SCL MPU6050 SCL IMU clock line
GPIO10 Digital Out Status LED (optional) Connection indicator
3.3V Power HT7333 VOUT, MPU6050 VCC Regulated power rail
GND Ground Common ground All components share
USB-C USB Serial Flashing/debugging Built-in on DevKit

MPU6050 (GY-521) Pinout

Pin Function Connection Notes
VCC Power ESP32 3.3V 3.3V or 5V compatible
GND Ground Common GND -
SDA I2C Data GPIO4 Pull-up enabled internally
SCL I2C Clock GPIO5 Pull-up enabled internally
INT Interrupt Not used Future: motion detection
AD0 Address Select GND Sets I2C address to 0x68

Assembly Instructions

Step 1: Solder HT7333 LDO

  1. Identify pins: HT7333 (SOT-89 package)

    ┌───────┐
│ HT7333│
└┬─┬─┬──┘
 │ │ └── VOUT (3.3V output)
 │ └──── GND
 └────── VIN (3.0V-6.0V input)

  2. Solder to TP4056 OUT+ (VIN) and OUT- (GND)

  3. Connect VOUT to ESP32-C3 3.3V rail

Step 2: Connect Battery

  1. Solder JST connector to LiPo (red = +, black = -)
  2. Connect to TP4056 BAT+ and BAT-
  3. Important: Check polarity before connecting!

Step 3: Wire I2C to MPU6050

  1. Solder 4 wires (SDA, SCL, VCC, GND) from ESP32-C3 to MPU6050
  2. Use 22AWG silicone wire (flexible, ~10cm length)
  3. Test continuity with multimeter

Step 4: Install Voltage Divider

  1. Solder two 10kΩ resistors in series
  2. Connect high end to LiPo+ (or TP4056 OUT+)
  3. Connect midpoint to ESP32-C3 GPIO0
  4. Connect low end to GND
  5. Cover with heat shrink tubing

Step 5: Test Power Supply

  1. Without ESP32 connected: Measure HT7333 VOUT with multimeter
  2. Expected: 3.25V-3.35V (3.3V ±50mV)
  3. If correct, connect ESP32-C3 3.3V pin

Step 6: Flash Firmware

  1. Connect ESP32-C3 USB-C to computer
  2. Flash Master or Slave firmware via PlatformIO
  3. Open serial monitor (115200 baud)
  4. Verify IMU initialization: "MPU6050 initialized (0x68)"

Step 7: Calibrate IMU

  1. Place sensor on flat, level surface
  2. Power on, wait 10 seconds for stabilization
  3. Web UI (Master) or serial output (Slave) should show ~0.0° pitch/roll

Troubleshooting

Problem: ESP32 won't power on

Check:

  • LiPo voltage (should be 3.7V-4.2V)
  • HT7333 VOUT (should be 3.3V)
  • TP4056 protection (may shut down if overcharged/over-discharged)

Solution: Charge LiPo via TP4056 USB-C

Problem: I2C not detected (MPU6050 not found)

Check:

  • Wiring: SDA to GPIO4, SCL to GPIO5
  • I2C address: Run I2C scanner (should show 0x68)
  • Pull-ups: Enable internal pull-ups in firmware

Solution: Verify connections, re-solder if cold joints

Problem: Battery percentage reads 0% or 255%

Check:

  • Voltage divider wiring (two 10kΩ resistors in series)
  • ADC pin (GPIO0) connection to midpoint
  • ADC code calibration (3.3V ADC reference)

Solution: Measure voltage at GPIO0 with multimeter (should be LiPo voltage / 2)

Problem: IMU angles drift over time

Check:

  • Complementary filter alpha (should be 0.98)
  • IMU temperature (MPU6050 sensitive to >15°C delta from calibration)
  • Vibration isolation (sensor should be firmly mounted)

Solution: Recalibrate at operating temperature, increase filter alpha to 0.99

Safety Warnings

⚠️ LiPo Battery Safety:

  • Never short-circuit LiPo terminals (fire/explosion risk)
  • Do not charge above 4.2V (TP4056 prevents this)
  • Do not discharge below 3.0V (TP4056 prevents this)
  • Store at 50-60% charge (3.7V-3.8V) if unused >1 week
  • Dispose of damaged/swollen batteries at hazardous waste facility

⚠️ Soldering Safety:

  • Use 300-350°C iron temperature (too hot damages components)
  • Solder in ventilated area (avoid flux fumes)
  • Do not touch soldering iron tip (obvious, but critical)

⚠️ ESD Protection:

  • ESP32-C3 and MPU6050 are ESD-sensitive
  • Touch grounded metal before handling (discharge static)
  • Avoid working on carpets or synthetic fabrics

Bill of Materials (Per Node)

See hardware/schematics/bom.csv for complete BOM with Amazon ASINs and pricing.

Quick Summary:

  • ESP32-C3 DevKit: $6.50
  • MPU6050 IMU: $4.50
  • LiPo Battery (400mAh): $8.00
  • TP4056 Charger: $1.50
  • HT7333 LDO: $0.80
  • Resistors, wire, connectors: $2.00
  • Total per node: ~$23.30

Revision History

Version Date Changes
1.0.0 2026-01-22 Initial wiring diagram for MVP

SkyLogic AeroAlign - Precision Grounded.

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