Configuration¶

Everything you can set: the address, the part, the gas, the averaging, and the build options.

The driver has no configuration struct: each setting is a constructor argument or one call. Snippets are compiled from tests/docs/configuration.cpp.

Settings¶

Setting	How	Default
I2C address	Constructor, `SetAddress()`	`0x2A`; must match the ADDR strap (Hardware)
Part family	Constructor `family`	`Sf06`; replaced once the variant is known
Variant	`ReadProductIdentifier()`, `AssumeVariant()`	`Unknown`: O₂ and air only
Gas	`StartContinuous(gas)`	None; set per measurement
O₂ fraction	`StartContinuous(mix, o2)`, `UpdateConcentration()`	0 ‰; mixtures only, 0 to 1000 ‰
Averaging	`ConfigureAveraging(n)`	0, average-until-read; idle only; a reset restores it

Several sensors on one bus¶

// Two SFM4300 on one bus: ADDR to GND (0x2A) and ADDR to GND through 1.2 kOhm (0x2B).
sfm::Driver<MyI2c> inlet(i2c, sfm::addr::kSfm4300Default);
sfm::Driver<MyI2c> outlet(i2c, sfm::addr::kSfm4300Alt1);

Up to four SFM4300 share a bus, one per ADDR strap. Each driver object only holds a reference to the port, so they can share one port object. A soft reset is a general call: it resets every sensor on the bus at once.

Tell the driver which part is fitted¶

// The sensor is already measuring (the identifier is idle-only), and the board fits an SFM4300-20-P.
sfm::Driver<MyI2c> flow(i2c, sfm::addr::kSfm4300Default);
flow.AssumeVariant(sfm::Variant::Sfm4300_20_P);  // also sets the family (SF06)
if (!flow.Stop()) {                              // this driver did not start it, so stop it here
  return false;
}
return flow.StartContinuous(sfm::Gas::CO2).ok();

Use AssumeVariant() when the product identifier cannot be read, for example after an MCU reset while the sensor kept measuring. It sets the family too. Assume only the part the board really carries: the gas check is the only protection against reading CO₂ with a table the sensor does not have.

Compile-time constants¶

These live in inc/sfm_commands.hpp and follow the datasheet; you do not normally change them.

Constant	Value	Use
`sfm::timing::kFirstResultAfterStartMs`	12	Wait in `StartContinuous()`
`sfm::timing::kStopToIdleMs`	1	Wait in `Stop()` (the sensor needs up to 0.5 ms)
`sfm::timing::kAccuracySettleAfterStartMs`	30	Readings before this are a few percent off
`sfm::timing::kSoftResetMs`	20	Wait after an SF06 soft reset (16 ms typical)
`sfm::timing::kSfx6000SoftResetMs`	30	Wait after an SFx6000 soft reset
`sfm::timing::kMeasurementPeriodUs`	500	SF06 sample period
`sfm::timing::kMaxAveragingWindow`	128	Largest fixed-N window
`sfm::kTemperatureScalePerC`	200	Temperature counts per °C
`sfm::kFlowUnitSlm20C`	`0x0148`	The SFM4300's flow unit code

Build options¶

Option	Default	Effect
`HF_SFM_ENABLE_WARNINGS`	`OFF`	`-Wall -Wextra -Wpedantic` on targets that link `hf::sfm`
`HF_SFM_BUILD_TESTS`	`OFF`	Host unit tests and documentation snippets (Testing and CI)

Next: Porting.