18 Standardized Units Table

This document defines the mapping rules between user input units and standardized output units (pre-transmission calibration).

1. Scope and Source

• Standardization function: osfx_standardize_value(...)
• Data source: OpenSynaptic/libraries mirror (osfx_library_catalog)
• This table is a subset of common units, not a full dictionary.

2. User Input Fields (Unit-related)

In transmission interface osfx_glue_encode_sensor_auto(...):

• User provides: input_unit
• System outputs: out_unit (standard unit)

cmd is not a user-defined field (auto path is automatically determined by fusion_state).

3. Common Unit Mapping Table (Example)

User Input Unit	Meaning	Canonical Output Unit	Conversion Rule
kPa	kilopascal	Pa	value * 1000
Pa	pascal	Pa	identity
psi	pound-force/inch^2	Pa	library conversion
mm[Hg]	millimeter mercury	Pa	library conversion
cel	degree Celsius	K	value + 273.15
degF	degree Fahrenheit	K	(value - 32) * 5/9 + 273.15
%	percent	%	identity

Notes:

• library conversion means the coefficient/offset comes from library data, not recommended to hardcode in business side.

4. Prefix Rules

If unit supports prefix and library marks it as prefixable, prefix will be automatically parsed:

• Example: k + base unit (e.g., kPa)
• Whether prefix is actually supported depends on unit metadata can_take_prefix

5. Input Constraints and Recommendations

• input_unit must be recognizable string.
• Recommended for business side to consistently use standard abbreviations (e.g., kPa, cel, %).
• If unit is unrecognized, current implementation will pass through unit as-is without conversion; production scenarios recommend adding whitelist validation at upper layer.

6. Pre-Transmission Check (Unit Dimension)

1. Check if input_unit is in allowed set (recommend whitelist).
2. Call osfx_standardize_value(...) to verify convertibility.
3. Compare output out_unit to meet business expectations (e.g., pressure unified to Pa).
4. Verify standardized value is within business legal range.

7. Reference Code Snippet

double out_value = 0.0;
char out_unit[16];
if (!osfx_standardize_value(input_value, input_unit, &out_value, out_unit, sizeof(out_unit))) {
    // reject invalid input
}

8. Related Documentation

• Transmission field specification: docs/17-glue-step-by-step.md
• Examples cookbook: docs/16-examples-cookbook.md
• Architecture description: docs/02-architecture.md