Logic levels

The FDO2-G2 UART is 3.0 V signalling with 3.3 V absolute maximum on those pins (data sheet §2 / §4). Your MCU UART must not drive 5 V TTL into the sensor. Use level shifters or a 3.3 V-native host (for example ESP32-S3).

UART parameters

Parameter	Default	Notes
Baud	19200	Factory default after every power cycle
Data	8 bits
Parity	None
Stop	1 bit
Flow control	None

Higher baud is possible only after a successful #BAUD command (not implemented in this driver build).

Boot delay

The module needs on the order of one second after power-up before it accepts commands. The ESP32 example waits kFdo2G2PowerUpSettleMs (~1100 ms) before #VERS.

Connector

The data sheet references Molex 560020-0420 for the module harness. Route TX/RX/GND only after confirming pinout for your cable revision.

ESP32-S3 shipped examples (default)

The examples/esp32 apps map MCU TX → sensor RX and MCU RX ← sensor TX on **UART_NUM_1**: GPIO47 (TX), GPIO21 (RX), 19200 8N1. Change the template parameters on the Fdo2EspIdfUart<…> type alias if your board uses different pins.

Fast versus verbose reads

**#MOXY** — smallest response; ideal for high-rate control loops.
**#MRAW** — adds pressure, humidity, dphi, and intensities for diagnostics and for the documented O₂ ratio when P tracks vent-side pressure.

Next: CMake integration →