NETRA Device Firmware V1

ESP32-C6 spatial-sensing firmware for the NETRA wearable safety system

Ultrasonic ranging and six-axis motion telemetry, streamed as clean CSV over USB serial.

Built for Claude Community Events @ Impact Lab.

Hardware

The V1 sensor node combines:

Component	Purpose	Interface
PCBCupid Glyph C6 / ESP32-C6	Main controller and USB serial link	USB CDC
HC-SR04	Obstacle distance measurement, nominally 2–400 cm	Trigger/echo pulse
MPU6050	3-axis acceleration, 3-axis angular velocity, temperature	I²C at 0x68 or 0x69

The MPU6050 is read directly through Wire; no third-party sensor library is required.

Wearer movement tracking

NETRA does more than measure nearby obstacles. The device is worn by the user, so its MPU6050 continuously captures the wearer's three-axis acceleration and three-axis rotation. The firmware streams this motion telemetry to the companion debugger, where it can be used to detect movement, estimate gait intensity, follow orientation changes, and animate the user's motion inside a closed or indoor tracking environment.

This is relative inertial movement tracking rather than GPS-style absolute positioning. Long-term position estimation from an IMU alone will accumulate drift; the current system is designed for live movement state, posture/orientation response, and closed-environment visualization.

Pin map

Sensor pin	Board pin	GPIO	Direction	Notes
HC-SR04 VCC	5V	—	Power	Use the board's 5 V rail
HC-SR04 GND	GND	—	Power	All grounds must be common
HC-SR04 TRIG	D20	20	Output	10 µs trigger pulse
HC-SR04 ECHO	D15	15	Input	Must pass through a voltage divider
MPU6050 VCC	3V3	—	Power	Safe default for common breakout boards
MPU6050 GND	GND	—	Power	Common ground
MPU6050 SDA	SDA	4	I²C data	Internal address auto-detected
MPU6050 SCL	SCL	5	I²C clock	Bus runs at 100 kHz

Prototype connection

The breadboard prototype below shows the Glyph controller connected to the HC-SR04 ultrasonic sensor and MPU6050 IMU. Use the pin table above as the source of truth; jumper-wire colors may differ between builds.

Caution

The HC-SR04 echo output is approximately 5 V. Never connect it directly to an ESP32-C6 input. Use, for example, 1 kΩ from ECHO to GPIO 15 and 2 kΩ from GPIO 15 to GND to reduce the signal to approximately 3.3 V.

HC-SR04 ECHO ── 1 kΩ ──┬── GPIO 15
                       │
                      2 kΩ
                       │
                      GND

Build and upload

Arduino IDE

Follow the official PCBCupid Arduino IDE setup guide when preparing a Glyph board. The required setup is summarized here:

1. Install the latest Arduino IDE, preferably version 2.3 or newer.

2. Open File → Preferences and add this URL under Additional Boards Manager URLs:

   https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
   

3. Open Boards Manager, search for ESP32, and install esp32 by Espressif Systems. Use the newest available release or at least version 3.1.0.

4. Connect the Glyph C6 with a data/sync-capable USB cable.

5. Select Tools → Board → ESP32 Arduino → GLYPHC6. If that entry is unavailable, select ESP32C6 Dev Module.

6. Open Netra_Device_Firmware_V1.ino, enable Tools → USB CDC On Boot, and select the board's COM port under Tools → Port.

7. Click Verify and confirm compilation finishes successfully, then click Upload.

8. After upload, open Serial Monitor at 115200 baud.

If the COM port is missing, hold BOOT, press and release RESET while continuing to hold BOOT, then release BOOT after the board enters bootloader mode. Re-select the COM port and upload again.

Arduino CLI

Replace COM6 and the FQBN when using another board definition:

arduino-cli core update-index
arduino-cli core install esp32:esp32
arduino-cli compile --fqbn esp32:esp32:esp32c6 .
arduino-cli upload -p COM6 --fqbn esp32:esp32:esp32c6 .

Mechanical enclosure and 3D printing

Printable NETRA V1 enclosure and wearable-pod models are maintained separately from the firmware source under mechanical/. The directory contains six STL parts plus slicing, printing, dry-fit, and assembly instructions.

The interactive assembled-system viewer renders the printable enclosure together with the belt, controller, sensors, controls, battery, and pod components. It includes ghost-shell, part-visibility, rotate, fit, and exploded-view controls.

mechanical/stl/
├── pod_1027_left.stl
├── pod_1027_right.stl
├── v2_button_cap.stl
├── v3_knob.stl
├── v7_base.stl
└── v7_shell.stl

See the mechanical and 3D-printing guide before printing or installing electronics.

Serial protocol

The device publishes one row every 250 ms:

distance_cm,echo_us,ax_g,ay_g,az_g,gx_dps,gy_dps,gz_dps,temp_c,status
24.63,1436,0.012,-0.021,0.998,0.31,-0.18,0.07,28.41,RANGE_OK|IMU_OK

Field	Unit	Meaning
distance_cm	cm	Distance calculated from the HC-SR04 echo pulse
echo_us	µs	Raw ultrasonic round-trip pulse width
ax_g…az_g	g	Accelerometer axes
gx_dps…gz_dps	°/s	Gyroscope axes
temp_c	°C	IMU die temperature
status	—	Combined range and IMU health flags

RANGE_TIMEOUT indicates that no echo arrived within 30 ms. IMU_ERROR usually points to I²C wiring, power, or address trouble.

Use with the NETRA debugger

Install and run the companion Netra System Debugger V1 to visualize motion, sensor health, proximity, and the live 3D digital twin.

Only one application can own the serial port at a time. Close Arduino Serial Monitor before starting the debugger.

Quick checks

• At rest, the magnitude of (ax, ay, az) should be close to 1 g.
• Rotating the enclosure should change the gyroscope values.
• A flat target between 10 and 100 cm should produce a stable distance.
• If the board prints ROM download messages, tap reset and confirm USB CDC On Boot is enabled.

Repository layout

Netra_Device_Firmware_V1/
├── Netra_Device_Firmware_V1.ino
├── docs/images/
├── mechanical/
│   ├── README.md
│   ├── belt_system_viewer.html
│   └── stl/*.stl
├── .gitignore
└── README.md