Quick Start | Gas Sensor Docs

Prerequisites

Rust toolchain with thumbv7em-none-eabihf target
probe-rs for flashing (cargo install probe-rs-tools)
A USB-UART adapter (CH340 or FTDI) for the UART interface
A J-Link or ST-Link connected to the 10-pin SWD header (J3)

1. Clone the Repository

git clone https://github.com/yasimbt/gas-sensor-fw.git
cd gas-sensor-fw

2. Build and Flash

cd fw
cargo run --release

On boot the firmware sends:

{"cmd":"FW","data":"0.1.0"}

3. Verify UART Communication

Connect a USB-UART adapter: PA9 → RX, PA10 → TX, GND → GND. 9600 baud, 8N1.

import serial, json

ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=2)

def cmd(c, d=""):
    ser.write((json.dumps({"cmd": c, "data": d}) + "\n").encode())
    return json.loads(ser.readline())

print(cmd("FW"))        # {'cmd': 'ACK', 'data': '0.1.0'}
print(cmd("STATUS"))    # {'cmd': 'STATUS', 'data': '1021.50:UNCALIBRATED'}

4. Two-Point Calibration

Zero (clean air)

1. Expose sensor to clean air (0 ppm)
2. Poll STABILITY → wait until is_stable=1  (~30 s)
3. Send ZERO → baseline stored to flash

Span (known concentration)

1. Apply certified span gas cylinder (e.g. 25 ppm)
2. Wait T90 (~30–35 s)
3. Send SPAN:25 → ChA and ChB computed and applied simultaneously
4. Verify GAS reads ≈ 25 ppm
5. Remove gas → verify return to ≈ 0 ppm

Calibration survives power cycles (stored in flash page 63).

5. Read Concentration

print(cmd("GAS"))          # {'cmd': 'GAS', 'data': '24.87'}
print(cmd("TEMP"))         # {'cmd': 'TEMP', 'data': '23.6'}
print(cmd("STABILITY"))    # {'cmd': 'STABILITY', 'data': '1250:30:1'}

See UART Command Interface for the full command reference.