conversionFactor< TUser, TRaw > Struct Template Reference

Scale and translate signed/unsigned values to convert between "raw" & "user" values. More...

#include <units.h>

Public Member Functions
constexpr TUser	toUser (TRaw raw) const
	Convert a value from raw page value to user value.
constexpr TRaw	toRaw (TUser user) const
	Convert a value from a user value to raw page value.

Public Attributes
uint16_t	scale
	Scale factor, must be >0.
int16_t	translate
	Translation - can be negative.

Detailed Description

template<typename TUser, typename TRaw>
struct conversionFactor< TUser, TRaw >

Scale and translate signed/unsigned values to convert between "raw" & "user" values.

Terminology:

• A "raw" value is what is stored in the tune. E.g. Time in tenths of a millisecond
• A "user" value is our internal type. E.g. Time in microseconds

The scaling and translation values are used as follows

• rawValue = userValue / scale – translate
• userValue = (rawValue + translate) * scale

Typically these will be the same scale and translate values as specified in the TunerStudio configuration file (ini)

Rationale: It encapsulates all conversion factors and operations in one place

• Removes magic numbers from many calculations.
• Puts the necessary MISRA compliance code (E.g. casts) in one place
• Allows independent unit testing of the conversion code

Background: For memory footprint reasons, many tune parameters are stored using a smaller type than the full numeric range requires. E.g.

• RPM requires a uint16_t
• We can store some RPM boundaries as a uint8_t containing RPM/100. The trade off is a loss of precision.

See section 4.4.7, Scale and Translate, of the TunerStudio ECU definition manual.

Template Parameters

TUser	The type of a user value. E.g. int8_t
TRaw	The type of a raw value. E.g. uint8_t

Member Function Documentation

toRaw()

template<typename TUser , typename TRaw >

constexpr TRaw conversionFactor< TUser, TRaw >::toRaw ( TUser  user ) const

inlineconstexpr

Convert a value from a user value to raw page value.

It's the callers responsibility to make sure the converted value fits into the destination type

Here is the call graph for this function:

toUser()

template<typename TUser , typename TRaw >

constexpr TUser conversionFactor< TUser, TRaw >::toUser ( TRaw  raw ) const

inlineconstexpr

Convert a value from raw page value to user value.

It's the callers responsibility to make sure the converted value fits into the destination type after translation & scaling

Here is the call graph for this function:

Member Data Documentation

scale

template<typename TUser , typename TRaw >

uint16_t conversionFactor< TUser, TRaw >::scale

Scale factor, must be >0.

translate

template<typename TUser , typename TRaw >

int16_t conversionFactor< TUser, TRaw >::translate

Translation - can be negative.

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The documentation for this struct was generated from the following file:

• speeduino/units.h