Customize A2L Files

Customize A2L (ASAP2) files generated from Simulink models using the coder.asap2 and coder.mapping APIs, avoiding silent errors and undocumented pitfalls.

When to Use

• Adding or modifying COMPU_METHODs (LINEAR, RAT_FUNC, TAB_VERB, IDENTICAL)
• Creating or modifying GROUPs in the A2L file
• Converting STD_AXIS to COM_AXIS for lookup tables
• Adding BIT_OPERATION (LEFT_SHIFT, RIGHT_SHIFT, SIGN_EXTEND) to measurements
• Creating VARIANT_CODING (VarCriterion, VarCharacteristic)
• Excluding inports, outports, or struct elements from the A2L
• Removing DEFAULT_EVENT_LIST or other IF_DATA blocks
• Any customization passed via CustomEcuDescriptions to coder.asap2.export

When NOT to Use

• Reading or parsing existing A2L files (use Vehicle Network Toolbox a2lfile)
• Configuring XCP/CAN transport layers
• Setting up Simulink model code generation (storage classes, data dictionaries)
• General Embedded Coder build workflows without A2L customization

Core Workflow

Decision: Direct export vs. customization workflow

• No element customization needed (only configuration like excluding struct elements or DEFAULT_EVENT_LIST): call coder.asap2.export directly with name-value options. No getEcuDescriptions needed.
• Element customization needed (adding/modifying/deleting measurements, characteristics, groups, etc.): use the full getEcuDescriptions → customize → export workflow.

% === Path A: Config-only (no element changes) ===
load_system(modelName);
slbuild(modelName);
coder.asap2.export(modelName, SupportStructureElements=false, IncludeDefaultEventList=false);

% === Path B: Element customization ===
load_system(modelName);
slbuild(modelName);

% 1. Create ECU descriptions — pass ALL configuration options here
descObj = coder.asap2.getEcuDescriptions(modelName, ...
    SupportStructureElements=false, ...
    IncludeDefaultEventList=false);

% 2. Customize elements
add(descObj, newElement);
set(descObj, 'ElementType', 'Name', Prop=value);
info = get(descObj, 'ElementType', 'Name');
names = find(descObj, 'ElementType');
delete(descObj, 'ElementType', 'Name');

% 3. Export — MUST pass descObj back or all customizations are silently lost
coder.asap2.export(modelName, CustomEcuDescriptions=descObj);

Critical: When using Path B, omitting CustomEcuDescriptions=descObj in the export call silently discards all customizations with no error.

Critical: When using Path B, construction-time options (SupportStructureElements, etc.) CANNOT be passed to export alongside CustomEcuDescriptions — they must be passed to getEcuDescriptions.

Key Functions

Function	Purpose
coder.asap2.getEcuDescriptions	Create ECU description object (construction-time config)
coder.asap2.export	Export A2L file with customizations
coder.asap2.CompuMethod	Create computation method
coder.asap2.Characteristic	Create characteristic (parameter)
coder.asap2.Measurement	Create measurement (signal)
coder.asap2.Group	Create A2L group
coder.asap2.RecordLayout	Create record layout
coder.asap2.AxisInfo	Create axis points or axis descriptor
coder.asap2.VarCriterion	Create variant criterion
coder.asap2.VarCharacteristic	Create variant characteristic
coder.asap2.Function	Create FUNCTION object for grouping measurements/characteristics
coder.mapping.api.get	Get code mapping object (persistent settings)
setInport / setOutport	Control inport/outport A2L export (persistent)

See references/object-properties.md for mandatory fields, valid types, and creation order for each coder.asap2.* class.

Pattern Routing

Match the user's task to the correct reference for detailed guidance:

Task	Key Rule	Reference
Add COMPU_METHOD (RAT_FUNC, LINEAR, TAB_VERB)	RAT_FUNC COEFFS direction is PHYS→INT — invert the desired formula	references/compu-method-guidance.md
Convert STD_AXIS to COM_AXIS (shared breakpoints)	Use ForceShared=true on the Characteristic — do NOT manually create AXIS_PTS	references/customization-patterns.md
Add BIT_OPERATION to a measurement	Must set BOTH BitMask AND MaskData — either alone produces no output	references/customization-patterns.md
Exclude inports/outports persistently	Use coder.mapping.api + setInport/setOutport + slbuild	references/customization-patterns.md
Create VARIANT_CODING	Must create supporting CHARACTERISTIC objects (selection + variant-dependent) with RecordLayouts and CompuMethods BEFORE VarCriterion/VarCharacteristic. All multi-value properties must be string arrays (not char/cell).	references/variant-coding-guidance.md
Create Characteristic (CURVE, MAP, CUBOID)	RecordLayout struct array must match axis count for STD_AXIS types	references/object-properties.md
Create Measurement	Set DataType='SWORD', EcuAddress='@ECU_Address@name@', CompuMethodName='NO_COMPU_METHOD' as defaults	references/object-properties.md
Create Group	See mandatory fields and ROOT constraint	references/object-properties.md
Create RecordLayout	Struct array required for multi-axis types (MAP, CUBOID); single struct for VALUE/VAL_BLK	references/object-properties.md
Create AxisInfo / AXIS_PTS	Dual role: add(descObj, axisInfo) creates AXIS_PTS; characteristic.AxisInfo = [...] creates AXIS_DESCR	references/object-properties.md
Control construction-time options (SupportStructureElements, IncludeDefaultEventList, etc.)	Must pass at getEcuDescriptions() — cannot set after construction or pass to export with CustomEcuDescriptions	references/construction-time-properties.md

Release Requirements

Feature	Minimum Release
COMPU_METHOD, Measurement, Characteristic, BIT_OPERATION	R2022b
RecordLayout, AxisInfo (STD_AXIS, CUBOID)	R2023a
Group (ROOT groups)	R2023b
VarCriterion, VarCharacteristic (variant coding)	R2025a

If the user's release is too old, inform them. Do not attempt workarounds — the APIs do not exist on older releases.

Common Mistakes

These cause silent failures or incorrect calibration data. Always check before generating code:

Mistake	Why It's Wrong	Correct Approach
coder.asap2.export(modelName) without CustomEcuDescriptions=descObj	Silently discards all customizations — no error, exports default A2L	Always pass descObj back when using the customization workflow
RAT_FUNC Coefficients = [0 0.5 -40 0 0 1] for "PHYS = 0.5×INT - 40"	COEFFS is PHYS→INT, not INT→PHYS — produces the inverse conversion	Invert: INT = 2×PHYS + 80 → [0 2 80 0 0 1]. See references/compu-method-guidance.md
set(descObj, ..., 'CompuMethodName', name) before adding the CompuMethod	set() auto-creates a placeholder that blocks subsequent add()	delete() the auto-created placeholder, then add() the user's version
MaskData.Shift without BitMask	BIT_OPERATION block is only emitted when both are set	Always set BitMask (e.g., '0xFF') alongside MaskData
MaskData.Shift = 3 expecting LEFT_SHIFT	Positive = RIGHT_SHIFT; sign is counterintuitive	Use -3 for LEFT_SHIFT 3
Manually creating AXIS_PTS for STD→COM_AXIS	Unnecessary complexity; error-prone struct array handling	Use set(descObj, 'Characteristic', name, 'ForceShared', true)
descObj.SupportStructureElements = false	Not a settable property after construction	Pass at creation: getEcuDescriptions(mdl, SupportStructureElements=false)
VarAddress = '0x5000' (char vector)	Char vector silently produces empty output — no addresses, no criterion name	Must be string array: ["0x5000","0x5008"]
CompuVTabValues.Integers = [0,1,2]	Property does not exist	Use CompuVTabValues.Values = [0, 1, 2]
CompuVTabValues.Literals = {'A','B'} (cell array)	Accepted without error but exports 0 elements	Must be string array: ["A","B"]
Skipping slbuild after setInport/setOutport	Export silently produces stale A2L with old settings	Always slbuild after code mapping changes before export
Hardcoding EcuAddress = '0x0000'	Calibration tools cannot resolve the address at import time	Use '@ECU_Address@<elementName>@' for linker resolution
Leaving mandatory fields unset on new objects	Blank fields produce invalid A2L — calibration tools reject the file	See references/object-properties.md for required fields per class
Creating VarCriterion/VarCharacteristic without supporting CHARACTERISTICs	VARIANT_CODING references characteristics that don't exist — calibration tool rejects the file	Create selection CHARACTERISTIC (with TAB_VERB CompuMethod) and variant-dependent CHARACTERISTIC (with RecordLayout) BEFORE VarCriterion/VarCharacteristic. See references/variant-coding-guidance.md

Conventions

• Verify A2L output with fileread after export — use contains for additions, ~contains for deletions/exclusions
• Use string arrays (not char vectors or cell arrays) for all multi-value properties
• Pass all configuration at getEcuDescriptions() construction time
• Use ForceShared=true for STD→COM_AXIS (never build AXIS_PTS manually for this)
• Use delete(descObj, 'ElementType', 'Name') to remove auto-created placeholders — this is the only recovery from the auto-creation trap caused by set() on a reference name before the referenced object exists
• Prefer coder.mapping.api over coder.asap2 when settings should persist with the model

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