@nexgen-os/ocpp — the Open Charge Point Protocol ⇄ plain shapes

Reads what a charging station and its central system (CSMS) say to each other in the Open Charge Point Protocol, versions 1.6J and 2.0.1 (JSON frames over a WebSocket), into plain shapes any tool can use, and writes back what a central system sends to steer a station. MIT; no dependency, no connection, no clock, no database.

| OCPP | Shape | Notes | |---|---|---| | a frame [2, id, action, payload], [3, id, payload], [4, id, code, description, details] | Frame | readFrame(), writeFrame(), the round trip is exact | | BootNotification | StationIdentity | vendor, model, serial number, firmware; the meter of a 1.6 station; why a 2.0.1 station booted | | StatusNotification | ConnectorState | EVSE, connector, status in one vocabulary (available, preparing, charging, suspended_ev, suspended_evse, finishing, occupied, reserved, unavailable, faulted), the 1.6 error code; in 1.6 a connector is its own EVSE, 0 is the station | | MeterValues, transactionData, meterValue of a TransactionEvent | Reading | measurand (Energy.Active.Import.Register when omitted), phase, location, context, value, unit symbol; a 2.0.1 value scaled by its multiplier; signed data is skipped | | StartTransaction + its result, StopTransaction (1.6); TransactionEvent (2.0.1) | SessionRecord | one per transaction: EVSE and connector, start and end, energy (register at the end minus at the start), peak active power, id token and its type, stop reason | | SetChargingProfile and its answer | Schedule, { failure } | purpose (station_max, tx_default, tx, external_constraints), stack level, kind, recurrency, rate unit (W or A), start, duration, validity, transaction, periods; Accepted is no failure, Rejected, NotSupported, an error frame or no answer (a timeout) is one |

MEASURANDS says where a measurand goes in a model of devices and series: the quantity that holds it (consumption_energy for the register of energy imported, consumption_power, current, charge_level…), whether it is a register or an instant, and its unit. A measurand absent from it (voltage, frequency, reactive power) is still read, with no quantity.

import { readStationLog, writeSetChargingProfile, readProfileAnswer } from '@nexgen-os/ocpp';

const log = readStationLog(entries, '2.0.1');      // identity, states, readings, sessions, profiles
const request = writeSetChargingProfile(schedule, '1.6', 7);
const { failure } = readProfileAnswer(answerFrame); // null once accepted

readStationLog() pairs each call with its result by its id, so that a 1.6 transaction gets the id the central system gave it, and folds the messages of one transaction in order.

What it never does: open a WebSocket, answer a station, decide a limit, convert a unit the protocol does not define, or resolve an id token. An id token may identify a person: whoever keeps it decides how.

The schemas it is written from

The Open Charge Alliance publishes OCPP 1.6 (with its JSON schemas) and OCPP 2.0.1 (its Part 3, the JSON schemas of every message) on openchargealliance.org; the 2.0.1 specification and its schemas are published under the Creative Commons Attribution-NoDerivatives 4.0 International licence. This package does not copy the schema files: its types are written from them, keep their field names, and are tested on recorded frames of both versions (tests/fixtures/).

Into Nexgen OS, importStationLog() of the charging module records the sessions and stores the readings as series of the charger.