mm::node::DeviceParameter Struct Reference

A single object dictionary entry held by a Device. More...

#include <device_parameter.h>

Collaboration diagram for mm::node::DeviceParameter:

Public Member Functions
uint32_t	key () const
	Returns the packed (index, subindex) key used in the parameter map.
uint64_t	loadBits () const
	Loads the scalar cell. Lock-free, non-allocating — safe from the RT loop.
void	storeBits (uint64_t v) const
	Stores the scalar cell. Lock-free, non-allocating, relaxed — safe from the RT loop.
DeviceParameterValue	currentValue () const
	Returns the current value as a DeviceParameterValue, built on the spot.
template<typename T >
std::optional< T >	scalar () const
	Reads the value as T straight out of the cell. Lock-free, non-allocating.
std::vector< uint8_t >	rawValueBytes () const
	Returns the value's raw wire bytes at the object's declared width.
void	setRawValue (std::span< const uint8_t > bytes)
	Replaces the stored value with bytes, its raw little-endian wire encoding.
template<typename T >
std::expected< T, std::string >	getValue () const
	Returns the value as the requested type T.
std::expected< double, std::string >	numeric () const
	Returns the value coerced to a double, for any numeric parameter.
std::expected< void, std::string >	setValue (const DeviceParameterValue &v)
	Sets value, coercing v into the parameter's declared data type.
template<typename T >
std::expected< void, std::string >	setValue (const T &v)
	Strongly-typed setValue overload; wraps v and coerces as above.
bool	isReadable () const
	Whether the object is readable in any state (ETG.1000.6 ObjAccess read bits 0-2).
bool	inRange (const DeviceParameterValue &v) const
	Whether v lies within [minValue, maxValue].
DeviceParameterValue	clampToRange (const DeviceParameterValue &v) const
	Returns v clamped to [minValue, maxValue].

Public Attributes
uint16_t	index {}
	CoE object index.
uint8_t	subindex {}
	CoE object subindex.
std::string	name
	Textual description from ecx_readOE.
uint16_t	objectCode {}
	OTYPE_VAR / OTYPE_ARRAY / OTYPE_RECORD (ETG.1000.6 §5).
uint16_t	dataType {}
	ETG.1020 data type code (e.g. 0x0007 = UNSIGNED32).
uint16_t	bitLength {}
	Bit length of the value.
uint16_t	access {}
	ObjAccess bitfield (read/write per-state flags).
ParameterOrigin	origin {ParameterOrigin::ObjectDictionary}
	Where this definition came from.
ScalarCell	cell {}
	Scalar value, LSB-aligned little-endian, zero-extended.
std::vector< uint8_t >	rawValue {}
	Non-scalar value (string / byte array) as wire bytes.
SyncState	syncState {SyncState::Unknown}
	Freshness of the value relative to the device.
std::optional< uint32_t >	unit
	ETG.1004 unit code, when reported.
std::optional< DeviceParameterValue >	defaultValue
	Slave-reported default, when available.
std::optional< DeviceParameterValue >	minValue
	Slave-reported minimum, when available.
std::optional< DeviceParameterValue >	maxValue
	Slave-reported maximum, when available.

Detailed Description

A single object dictionary entry held by a Device.

Combines immutable schema (index, subindex, name, data type, bit length, access flags, object code) with a value that is overwritten by SDO upload or PDO exchange. value is initialised to the type-appropriate zero so callers can std::visit it directly without checking for a read.

Member Function Documentation

clampToRange()

DeviceParameterValue mm::node::DeviceParameter::clampToRange

(

const DeviceParameterValue &

v

)

const

Returns v clamped to [minValue, maxValue].

Clamps numerically and returns a value of the same alternative as v. Returns v unchanged when it is non-numeric or no numeric bounds apply.

currentValue()

DeviceParameterValue mm::node::DeviceParameter::currentValue

(

)

const

Returns the current value as a DeviceParameterValue, built on the spot.

The value is stored as wire bytes, so the variant is reconstructed here rather than held: one switch on the immutable dataType turns the bytes into the right alternative — the same mapping defaultValueForDataType has always used to choose it. That is what keeps a value in exactly one home, so the HTTP view and a cyclic task's view can never disagree.

Off-RT only, by cost rather than by safety: it may allocate (a string or byte-array parameter). A cyclic task reads loadBits instead.

getValue()

template<typename T >

std::expected< T, std::string > mm::node::DeviceParameter::getValue ( ) const

inline

Returns the value as the requested type T.

Type-exact: T must be the alternative dataType maps to (e.g. uint32_t for an UNSIGNED32 parameter — booleans are stored as uint8_t, see defaultValueForDataType). Use numeric() when you only need a number and do not care about the exact width.

Returns

The value, or an error string if T is not the parameter's alternative.

inRange()

bool mm::node::DeviceParameter::inRange

(

const DeviceParameterValue &

v

)

const

Whether v lies within [minValue, maxValue].

Bounds are compared via numeric coercion. Returns true when v is non-numeric or when a bound is unset/non-numeric (i.e. no constraint to violate).

isReadable()

bool mm::node::DeviceParameter::isReadable ( ) const

inline

Whether the object is readable in any state (ETG.1000.6 ObjAccess read bits 0-2).

Write-only objects (e.g. a command/trigger sub-object) report no read bits; an SDO upload of one aborts, so a bulk value refresh should skip them rather than log a spurious failure.

key()

uint32_t mm::node::DeviceParameter::key ( ) const

inline

Returns the packed (index, subindex) key used in the parameter map.

loadBits()

uint64_t mm::node::DeviceParameter::loadBits ( ) const

inline

Loads the scalar cell. Lock-free, non-allocating — safe from the RT loop.

See ScalarCell for why relaxed ordering is the whole requirement here.

numeric()

std::expected< double, std::string > mm::node::DeviceParameter::numeric

(

)

const

Returns the value coerced to a double, for any numeric parameter.

The "don't worry about the type" accessor — handy because most parameters are numbers of varying width.

Returns

The numeric value, or an error string if value is a string / raw bytes.

rawValueBytes()

std::vector< uint8_t > mm::node::DeviceParameter::rawValueBytes

(

)

const

Returns the value's raw wire bytes at the object's declared width.

The storage-level getter, and the inverse of setRawValue: a scalar is unpacked from the cell, a non-scalar returned as stored. Prefer it over encodeSdoBytes(dataType, currentValue()) — storage is already bytes, so that route decodes and re-encodes for nothing.

One difference worth knowing for strings: this returns what the slave actually sent, padding included, where currentValue() strips the trailing NUL/space padding ETG.1000.6 allows.

scalar()

template<typename T >

std::optional< T > mm::node::DeviceParameter::scalar ( ) const

inline

Reads the value as T straight out of the cell. Lock-free, non-allocating.

The RT-callable read: one relaxed atomic load and a copy, with no lookup, no decode into a variant and no error string to build. T must be the alternative dataType maps to — int32_t for an INTEGER32 object, uint8_t for a BOOLEAN — and a mismatch, or a non-scalar parameter, reads as nullopt rather than as a wrong number.

A parameter never written reads as zero, not nullopt: syncState is where "never read" is recorded, and a control loop wants a number it can act on.

setRawValue()

void mm::node::DeviceParameter::setRawValue

(

std::span< const uint8_t >

bytes

)

Replaces the stored value with bytes, its raw little-endian wire encoding.

The storage-level setter: no coercion, no decoding, no syncState change — it takes the bytes an SDO upload or the process image already produced and puts them where isScalarDataType says they belong. setValue is the typed counterpart.

setValue() [1/2]

std::expected< void, std::string > mm::node::DeviceParameter::setValue

(

const DeviceParameterValue &

v

)

Sets value, coercing v into the parameter's declared data type.

Numeric inputs are static_cast into the alternative matching dataType, so setValue(5) works regardless of whether the parameter is UNSIGNED8 or UNSIGNED32 — unlike a bare variant assignment, which would store the wrong alternative. Does not touch syncState; the caller decides that.

Returns

Void on success, or an error string when v cannot be coerced (e.g. a string into a numeric parameter, or a number into a string parameter).

setValue() [2/2]

template<typename T >

std::expected< void, std::string > mm::node::DeviceParameter::setValue ( const T &  v )

inline

Strongly-typed setValue overload; wraps v and coerces as above.

storeBits()

void mm::node::DeviceParameter::storeBits ( uint64_t  v ) const

inline

Stores the scalar cell. Lock-free, non-allocating, relaxed — safe from the RT loop.

Member Data Documentation

access

uint16_t mm::node::DeviceParameter::access {}

ObjAccess bitfield (read/write per-state flags).

bitLength

uint16_t mm::node::DeviceParameter::bitLength {}

Bit length of the value.

cell

ScalarCell mm::node::DeviceParameter::cell {}

Scalar value, LSB-aligned little-endian, zero-extended.

dataType

uint16_t mm::node::DeviceParameter::dataType {}

ETG.1020 data type code (e.g. 0x0007 = UNSIGNED32).

defaultValue

std::optional<DeviceParameterValue> mm::node::DeviceParameter::defaultValue

Slave-reported default, when available.

index

uint16_t mm::node::DeviceParameter::index {}

CoE object index.

maxValue

std::optional<DeviceParameterValue> mm::node::DeviceParameter::maxValue

Slave-reported maximum, when available.

minValue

std::optional<DeviceParameterValue> mm::node::DeviceParameter::minValue

Slave-reported minimum, when available.

name

std::string mm::node::DeviceParameter::name

Textual description from ecx_readOE.

objectCode

uint16_t mm::node::DeviceParameter::objectCode {}

OTYPE_VAR / OTYPE_ARRAY / OTYPE_RECORD (ETG.1000.6 §5).

origin

ParameterOrigin mm::node::DeviceParameter::origin {ParameterOrigin::ObjectDictionary}

Where this definition came from.

rawValue

std::vector<uint8_t> mm::node::DeviceParameter::rawValue {}

Non-scalar value (string / byte array) as wire bytes.

subindex

uint8_t mm::node::DeviceParameter::subindex {}

CoE object subindex.

syncState

SyncState mm::node::DeviceParameter::syncState {SyncState::Unknown}

Freshness of the value relative to the device.

unit

std::optional<uint32_t> mm::node::DeviceParameter::unit

ETG.1004 unit code, when reported.

---

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

• libs/node/device_parameter.h
• libs/node/device_parameter.cc