crankMaths.h File Reference

Crank revolution based mathematical functions. More...

#include "maths.h"
#include "board_definition.h"

Go to the source code of this file.

Classes
struct	angle_converter_factors_t
	The factors used to convert between crank angle & time. These are derived from the crank revolution time. More...

Functions
static uint16_t	RpmFromRevolutionTimeUs (uint32_t revolutionTime)
	Converts a crank revolution time to engine speed.
static int16_t	ignitionLimits (int16_t angle)
	Makes one pass at nudging the angle to within [0,CRANK_ANGLE_MAX_IGN].
angle_converter_factors_t	calculateAngleConverterFactors (uint32_t revolutionTime) noexcept
	Calculate the angle<-->time conversion factors for a crank revolution time.
void	applyAngleConverterFactors (const angle_converter_factors_t &factors) noexcept
	Set the factors used by the degree<-->angle conversions.
void	setAngleConverterRevolutionTime (uint32_t revolutionTime) noexcept
	Set the revolution time, from which some of the degree<-->angle conversions are derived.
uint32_t	angleToTime (uint16_t angle) noexcept
	Converts angular degrees to the time interval that amount of rotation will take at current RPM.
COMPARE_TYPE	angleToTimerTicks (uint16_t angle) noexcept
	Converts angular degrees to the equivalent timer ticks at current RPM.
uint16_t	timeToAngle (uint32_t time) noexcept
	Converts a time interval in microsecods to the equivalent degrees of angular (crank) rotation at current RPM.

Variables
static constexpr uint32_t	MICROS_PER_DEG_1_RPM = UDIV_ROUND_CLOSEST(MICROS_PER_MIN, 360UL, uint32_t)
	At 1 RPM, each degree of angular rotation takes this many microseconds.
static constexpr uint16_t	MAX_RPM = 18000U
	The maximum rpm that the ECU will attempt to run at.
static constexpr uint16_t	MIN_RPM = (uint16_t)UDIV_ROUND_UP(MICROS_PER_DEG_1_RPM, (uint32_t)UINT16_MAX/16UL, uint32_t)
	Absolute minimum RPM that the crank math (& therefore all of Speeduino) can be used with.
static constexpr uint16_t	MIN_REVOLUTION_TIME = MICROS_PER_MIN/MAX_RPM
	Minimum time in µS that one crank revolution can take.
static constexpr uint32_t	MAX_REVOLUTION_TIME = MICROS_PER_MIN/MIN_RPM
	Maximum time in µS that one crank revolution can take.
int16_t	CRANK_ANGLE_MAX_IGN
	The number of crank degrees that the system tracks ignition over.
int16_t	CRANK_ANGLE_MAX_INJ
	The number of crank degrees that the system tracks fuel injection over.

Detailed Description

Crank revolution based mathematical functions.

Function Documentation

angleToTime()

uint32_t angleToTime ( uint16_t  angle )

noexcept

Converts angular degrees to the time interval that amount of rotation will take at current RPM.

Based on angle of [0,720] and min/max RPM, result ranges from 9 (MAX_RPM, 1 deg) to 2926828 (MIN_RPM, 720 deg)

Parameters

angle

Angle in degrees

Returns

Time interval in uS

angleToTimerTicks()

COMPARE_TYPE angleToTimerTicks ( uint16_t  angle )

noexcept

Converts angular degrees to the equivalent timer ticks at current RPM.

Parameters

angle

Angle in degrees

Returns

Number of timer ticks

applyAngleConverterFactors()

void applyAngleConverterFactors ( const angle_converter_factors_t &  factors )

noexcept

Set the factors used by the degree<-->angle conversions.

Note

If an ISR could be converting angles, call this from within an ATOMIC() block.

Parameters

factors

The factors to use. See calculateAngleConverterFactors()

calculateAngleConverterFactors()

angle_converter_factors_t calculateAngleConverterFactors ( uint32_t  revolutionTime )

noexcept

Calculate the angle<-->time conversion factors for a crank revolution time.

This does not change the factors in use (see applyAngleConverterFactors()), so the (relatively slow) divisions can be done outside of a critical section.

Parameters

revolutionTime

The crank revolution time in uS. Zero results in zero factors.

ignitionLimits()

static int16_t ignitionLimits ( int16_t  angle )

inlinestatic

Makes one pass at nudging the angle to within [0,CRANK_ANGLE_MAX_IGN].

Parameters

angle

A crank angle in degrees

Returns

int16_t

RpmFromRevolutionTimeUs()

static uint16_t RpmFromRevolutionTimeUs ( uint32_t  revolutionTime )

inlinestatic

Converts a crank revolution time to engine speed.

Parameters

revolutionTime

The time in µS that one crank revolution takes. Zero if the engine speed is unknown

Returns

The engine speed in RPM, rounded to the closest integer & limited to MAX_RPM. Zero if revolutionTime is zero

setAngleConverterRevolutionTime()

void setAngleConverterRevolutionTime ( uint32_t  revolutionTime )

noexcept

Set the revolution time, from which some of the degree<-->angle conversions are derived.

Shorthand for applyAngleConverterFactors(calculateAngleConverterFactors(revolutionTime))

Parameters

revolutionTime

The crank revolution time.

timeToAngle()

uint16_t timeToAngle ( uint32_t  time )

noexcept

Converts a time interval in microsecods to the equivalent degrees of angular (crank) rotation at current RPM.

Inverse of angleToTime

Parameters

time	Time interval in uS

Returns

Angle in degrees

Variable Documentation

CRANK_ANGLE_MAX_IGN

int16_t CRANK_ANGLE_MAX_IGN

extern

The number of crank degrees that the system tracks ignition over.

CRANK_ANGLE_MAX_INJ

int16_t CRANK_ANGLE_MAX_INJ

extern

The number of crank degrees that the system tracks fuel injection over.

MAX_REVOLUTION_TIME

constexpr uint32_t MAX_REVOLUTION_TIME = MICROS_PER_MIN/MIN_RPM

staticconstexpr

Maximum time in µS that one crank revolution can take.

Note

: many calculations are done over 2 revolutions (cycles), in which case this would be doubled

MAX_RPM

constexpr uint16_t MAX_RPM = 18000U

staticconstexpr

The maximum rpm that the ECU will attempt to run at.

It is NOT related to the rev limiter, but is instead dictates how fast certain operations will be allowed to run. Lower number gives better performance

MICROS_PER_DEG_1_RPM

constexpr uint32_t MICROS_PER_DEG_1_RPM = UDIV_ROUND_CLOSEST(MICROS_PER_MIN, 360UL, uint32_t)

staticconstexpr

At 1 RPM, each degree of angular rotation takes this many microseconds.

MIN_REVOLUTION_TIME

constexpr uint16_t MIN_REVOLUTION_TIME = MICROS_PER_MIN/MAX_RPM

staticconstexpr

Minimum time in µS that one crank revolution can take.

Note

: many calculations are done over 2 revolutions (cycles), in which case this would be doubled

MIN_RPM

constexpr uint16_t MIN_RPM = (uint16_t)UDIV_ROUND_UP(MICROS_PER_DEG_1_RPM, (uint32_t)UINT16_MAX/16UL, uint32_t)

staticconstexpr

Absolute minimum RPM that the crank math (& therefore all of Speeduino) can be used with.

This is dictated by the use of uint16_t as the base type for storing time --> angle conversion factor (degreesPerMicro)