1. Separate sensing conversion from physical-value calculation
The BMP390 functional description identifies a pressure-sensing element and a mixed-signal ASIC. The ASIC performs analog-to-digital conversions and provides conversion results together with sensor-specific compensation data through a digital interface. These resources have different roles. The conversion result represents the sensing response in the device's raw data form. The compensation data provides information used when that response is translated into the physical pressure and temperature values described by the datasheet. The raw data and the compensation parameters consequently belong to the same calculation chain without being the same data class. Their availability through one interface preserves the distinction between a sensing result and information used to interpret that result.
A digital output description consequently does not mean that every value available through the interface is already a compensated physical reading. Bosch's compensation section explicitly distinguishes raw output from the values calculated using compensation. The interface is the delivery path for information; the type of information determines its meaning. Keeping that distinction visible prevents a raw conversion, a stored parameter and a calculated result from becoming one undifferentiated sensor value. This is a specific account of the BMP390 resource chain, without reproducing a conversion formula, data format or firmware implementation.
2. Locate factory coefficients in nonvolatile storage
Bosch states that the compensation coefficients are stored in the device's nonvolatile memory during production. They are sensor-specific because individual sensing elements behave differently. Their purpose is therefore tied to the particular sensor's response, rather than to a generic customer application image. A coefficient is also different from a measurement sample: it belongs to the information used for compensation, while the sample comes from a conversion of the sensing response.
These distinctions separate origin, storage and use. Production establishes the coefficient context, nonvolatile memory retains the information, and the compensation calculation uses it with raw output. None of those roles turns the coefficients into a time-stamped account of current pressure. Nor does a description of their factory origin identify customer firmware or establish that the complete measurement system has a current calibration certificate. The useful technical description names the coefficients as retained sensor resources. It does not need their individual values, storage addresses or a method for reading or changing them to explain why they differ from both application instructions and measurement results.
3. Keep temperature compensation in the pressure chain
The datasheet's introductory compensation explanation also identifies a temperature value carried into pressure compensation. This gives temperature a functional role within the pressure-result chain, beyond being a separately reported environmental quantity. The pressure calculation is not described as depending on a pressure conversion alone. Its compensation context includes temperature-related information, with the sensor-specific coefficients serving their separate parameter role. A concise description of the output chain should preserve that dependency rather than presenting pressure and temperature as entirely unrelated labels.
The intermediate value is distinct from both its inputs and its later use. It is produced within the temperature-compensation context and contributes to the pressure-compensation context. Calling it a factory coefficient would confuse a calculated resource with retained production data; calling every available temperature-related item a new measurement would confuse calculation with acquisition. These distinctions explain the flow of information without naming an internal variable or reconstructing the manufacturer's code. They also add a different subject from pressure-reference type or amplified-versus-unamplified classification: the question here is how the named device's compensation resources participate in producing physical values.
4. Distinguish coefficient access from a fresh measurement
Bosch's sleep-mode prose provides a particularly clear separation between information access and measurement activity. It states that no measurements are performed in sleep mode, while compensation coefficients remain readable. The documented availability of coefficient data therefore cannot, on its own, establish that a fresh sensing conversion occurred. Storage access and measurement acquisition are separate functions, even though both belong to the same sensor and may be discussed through the same digital interface.
This difference also clarifies the word calibration in a product description. Factory compensation information describes resources established during production. A current measurement concerns a conversion and its resulting data. A current calibration certificate is evidence about an identified measurement item under its stated assessment context. The existence of the first is not the occurrence of the second or the evidence required for the third. Keeping those subjects separate yields a coherent description of raw conversion, retained coefficients, temperature-dependent compensation and measurement activity. It supplies no measurement command, access sequence, numerical accuracy or finding that a removed BMP390 remains calibrated.
Sources and further reading
Bosch BMP390 BST-BMP390-DS002-07 Rev 1.7, March 2021: bounded functional, sleep-access, raw/compensated-output, production-coefficient and temperature-intermediate prose on physical pages 9, 11, 27, 28 and 55. Registers, coefficients, formulas and implementation code are excluded.