@emdzej/ncsx-ecu-select

@emdzej/ncsx-ecu-select

Given a chassis bundle and the car's ASW bit set, returns the list of SGs (ECUs) that are in scope — the ones whose AUFTRAGSAUSDRUCK predicate matches.

This is step 2 of the coding flow: before you can code or read any SG, you need to know which SGs the car actually has. NCS Expert calls this "Process ECU" and walks the same SGAUSWAHL_* blocks in the same order; this package is the deterministic equivalent.

NCSEXPER equivalent: coapiScanAllSgFromBr (with coapiScanAllSgFromZcs being the same function fed by a different ASW source).

Spec: ../../docs/ecu-selection.md §3.4.

What it does

Walks the three SGAUSWAHL_* blocks of <BR>SGET.000 in most-specific-first order:

1. SGAUSWAHL_VMSGBD — variant + module-variant + SGBD-specific rows.
2. SGAUSWAHL_SGBD — module-variant + SGBD-specific rows.
3. SGAUSWAHL_VM — variant-only fallback.

For each row, evaluates the AUFTRAGSAUSDRUCK byte-coded predicate against the supplied AswSet (via @emdzej/ncsx-predicate). Matching rows are returned as a SelectedSg[] with the resolved (sgName, cabd, sgbd, …) tuple.

By default, deduplicates by sgName so the most-specific row wins for each SG.

Install

pnpm add @emdzej/ncsx-ecu-select
# or:
"@emdzej/ncsx-ecu-select": "workspace:*"

Quick start

import { loadChassis } from '@emdzej/ncsx-chassis';
import { nodeChassisSource } from '@emdzej/ncsx-chassis/node';
import { faToAsw } from '@emdzej/ncsx-fa-asw';
import { selectEcus } from '@emdzej/ncsx-ecu-select';

const chassis = await loadChassis(nodeChassisSource('…/DATEN'), 'E46');
const asw = faToAsw('0205 0502 0524', { chassis });
const selected = selectEcus(chassis, asw);

for (const sg of selected) {
  console.log(`${sg.source}  ${sg.sgName}  CBD=${sg.cbd}  CABD=${sg.cabd}  SGBD=${sg.sgbd}`);
}

API

Export	Purpose
selectEcus(chassis, asw, opts?)	Walk SGAUSWAHL_* and return matched SGs
SelectedSg	One row in the result
SelectionSource	'VMSGBD' | 'SGBD' | 'VM' — which block matched

SelectedSg

interface SelectedSg {
  sgName: string;       // logical SG short name (matches SGFAM)
  cbd: string;          // CBD coding bundle name
  cabd?: string;        // CABD coding module name (omitted for VM rows)
  sgbd?: string;        // EDIABAS SGBD file (omitted for VM rows)
  umrsg: string;        // conversion-SG hint
  vmg?: string;         // module-variant (omitted for SGBD rows)
  index: number | null;
  source: SelectionSource;  // which SGAUSWAHL_* block this came from
}

selectEcus options

selectEcus(chassis, asw, {
  dedupeBySgName: true,         // most-specific row wins per SG (default true)
  maxPredicateLength: 100,      // skip predicates longer than this (safety)
  onWarning: (msg) => { … },    // surface skip reasons (rare; mostly malformed predicates)
});

When to reach for it

• Building a "Pick a module" UI — feed selected into a list.
• Driving a multi-SG batch operation (planCoding does this internally).
• Debugging "why isn't NCS Expert seeing my module?" — compare selectEcus output against what NCS Expert lists for your VIN.

Tie-breaker semantics

When dedupeBySgName: true (the default):

• The walk order is most-specific → least-specific (VMSGBD → SGBD → VM).
• The first (sgName) to match wins; subsequent rows for the same SG are skipped.
• This matches NCSEXPER's behaviour: a VMSGBD-specific override beats a VM fallback.

Set dedupeBySgName: false if you want every matching row (e.g. for diagnostic "why didn't my preferred row match?" exploration).

Related

• @emdzej/ncsx-chassis — supplies the SGET.000 data.
• @emdzej/ncsx-fa-asw — produces the AswSet this consumes.
• @emdzej/ncsx-predicate — used to evaluate each row's AUFTRAGSAUSDRUCK.
• @emdzej/ncsx-coder — top-level orchestrator that calls this internally.
• Spec: ../../docs/ecu-selection.md.