Esp32

AEGIS v2 — ESP32 Load-Cell Firmware

ESP32 firmware that reads an array of HX711 load-cell amplifiers and streams per-bin weights to the host PC over USB serial. It is the device-side counterpart to the host reader at aegis-v2/integration/src/sensing/loadcell.py.

What it does

Each load cell maps to one bin (bin_{row}_{col}). The ESP32 reads every cell, applies per-bin calibration, and emits one line of JSON per cycle (~10 Hz):

{"bins": {"bin_0_0": 123.4, "bin_0_1": 80.1, "bin_1_0": 0.0}}

Weights are in grams. The format, keys, and 115200 baud exactly match the contract the host parser expects.

Hardware

• 1× ESP32 dev board (any variant).
• 1× HX711 amplifier + load cell per bin (7 bins for the default [4, 3] layout).
• Each HX711 needs VCC (3.3V), GND, DT (data), SCK (clock). DT/SCK go to the GPIO pins listed in BINS[]; VCC/GND share the ESP32's 3.3V and GND rails.

The example pins in aegis_loadcells/aegis_loadcells.ino are a starting point — edit the BINS[] table to match your actual wiring and layout.

Build & flash (Arduino IDE)

1. Install ESP32 board support: File → Preferences → add https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json to Additional Board Manager URLs, then install esp32 in Tools → Board → Boards Manager.
2. Install the HX711 library: Tools → Manage Libraries → "HX711" by Bogdan Necula (bogde/HX711).
3. Open aegis_loadcells/aegis_loadcells.ino.
4. Select your board under Tools → Board and the serial port under Tools → Port, then click Upload.

(arduino-cli equivalent:)

arduino-cli core install esp32:esp32
arduino-cli lib install "HX711"
arduino-cli compile -b esp32:esp32:esp32 esp32/aegis_loadcells
arduino-cli upload  -b esp32:esp32:esp32 -p /dev/ttyUSB0 esp32/aegis_loadcells

Calibration

Open the Arduino Serial Monitor at 115200 baud (newline line-ending). The firmware streams JSON, and also accepts these one-line commands:

To calibrate a cell:

1. Send t with empty bins.
2. Place a known weight (e.g. 500 g) on bin index i.
3. Send c i 500. The firmware prints the computed scale factor.
4. Paste that value into the scale column of BINS[] and re-flash so it persists across power cycles.

Command replies start with #, so the host parser ignores them harmlessly.

Connect to the host pipeline

Enable load cells in aegis-v2/integration/config/settings.yaml:

sensing:
  loadcells:
    enabled: true
    port: "/dev/ttyUSB0"   # ESP32 USB device (Windows: "COM3", macOS: "/dev/tty.usbserial-*")
    baudrate: 115200
    stale_after: 2.0

Find the port with ls /dev/ttyUSB* /dev/ttyACM* (Linux) or Device Manager (Windows). The host reads weights on a background thread and the dashboard shows live per-bin grams.

Quick test without the pipeline

Any serial monitor at 115200 baud will show the JSON stream:

# Linux/macOS
screen /dev/ttyUSB0 115200      # Ctrl-A then K to quit
# or
python3 -m serial.tools.miniterm /dev/ttyUSB0 115200