# Getting Started with OCPP1.6

## Integrate this library with your Charging Station Implementation for OCPP1.6

OCPP is a protocol that affects, controls and monitors many areas of a charging station's operation.

If you want to integrate this library with your charging station implementation, you have to register a couple of **callbacks** and integrate **event handlers**. This is necessary for the library to interact with your charging station according to the requirements of OCPP.

Libocpp needs registered **callbacks** in order to execute control commands defined within OCPP (e.g Reset.req or RemoteStartTransaction.req)

The implementation must call **event handlers** of libocpp so that the library can track the state of the charging station and trigger OCPP messages accordingly (e.g. MeterValues.req , StatusNotification.req)

Your reference within libocpp to interact is a single instance to the class ocpp::v16::ChargePoint ([ChargePoint](include/ocpp/v16/charge_point.hpp)) defined in `ocpp/v16/charge_point.hpp` for OCPP 1.6.

### Overview of the required callbacks and events and what libocpp expects to happen

The following section will give you a high level overview of how to integrate libocpp with your application. Please use the [Doxygen Documentation](#building-the-doxygen-documentation) as an additional source for the ChargePoint API.

In EVerest the OCPP module leverages several other modules to perform tasks that relate to authorization, reservations, charging session handling and system tasks like rebooting or firmware updates.

- Auth orchestrates authorization, utilizing different token providers like RFID reads and token validators. Libocpp mainly acts as a token validator, but in the case of RemoteStartTransactions it acts as a token provider as well
- EvseManager manages the charging session and charging state machine by communicating with a "board support package", a driver for the charging hardware that abstracts away the control pilot, relay control, power meters, etc. The EvseManager also handles reservations.
- System handles firmware updates, log uploads and resets

The following sections explain the steps you can follow to implement their functionality on your own and integrate the libocpp directly into your charging station software without relying on EVerest. However, in most cases it's much easier to write an EVerest driver using the *EVerest/interfaces/board_support_AC.yaml* interface.

#### ChargePoint() constructor

The main entrypoint for libocpp for OCPP1.6 is the ocpp::v16::ChargePoint constructor.
This is defined in `v16/charge_point.hpp` and takes the following parameters:

- config: a std::string that contains the libocpp 1.6 config. There are example configs that work with a [SteVe](https://github.com/steve-community/steve) installation for example `config/v16/config-docker.json`.

- share_path: a std::filesystem path containing the path to the OCPP modules folder, for example pointing to */usr/share/everest/modules/OCPP*. This path contains the following files and directories and is installed by the libocpp  install target:

  ```bash
  .
  ├── config-docker.json
  ├── config-docker-tls.json
  ├── config.json
  ├── init.sql
  ├── logging.ini
  └── profile_schemas
      ├── Config.json
      ├── Core.json
      ├── FirmwareManagement.json
      ├── Internal.json
      ├── LocalAuthListManagement.json
      ├── PnC.json
      ├── Reservation.json
      ├── Security.json
      ├── SmartCharging.json
      └── Custom.json
  ```

  Here you can find:
  - the aforementioned config files

  - a *logging.ini* that is needed to initialize logging with Everest::Logging::init(path_to_logging_ini, "name_of_binary")

  - a *init.sql* file which contains the database schema used by libocpp for its sqlite database

  - and a *profile_schemas* directory. This contains json schema files that are used to validate the libocpp config. The schemas are split up according to the OCPP1.6 feature profiles like Core, FirmwareManagement and so on. Additionally there is a schema for "Internal" configuration options (for example the ChargePointId, or CentralSystemURI). A "PnC" schema for the ISO 15118 Plug & Charge with OCPP 1.6 Application note, a "Security" schema for the OCPP 1.6 Security Whitepaper (3rd edition) and an exemplary "Custom" schema are provided as well. The Custom.json could be modified to be able to add custom configuration keys. Finally there's a Config.json schema that ties everything together

- user_config_path: this points to a "user config", which we call a configuration file that's merged with the config that's provided in the "config" parameter. Here you can add, remove and overwrite settings without modifying the config passed in the first parameter directly. This is also used by libocpp to persistently modify config entries that are changed by the CSMS that should persist across restarts.

- database_path: this points to the location of the sqlite database that libocpp uses to keep track of connector availability, the authorization cache and auth list, charging profiles and transaction data

- sql_init_path: this points to the aforementioned init.sql file which contains the database schema used by libocpp for its sqlite database

- message_log_path: this points to the directory in which libocpp can put OCPP communication logfiles for debugging purposes. This behavior can be controlled by the "LogMessages" (set to true by default) and "LogMessagesFormat" (set to ["log", "html", "session_logging"] by default, "console" and "console_detailed" are also available) configuration keys in the "Internal" section of the config file. Please note that this is intended for debugging purposes only as it logs all communication, including authentication messages.

- evse_security: this is a pointer to an implementation of the `common/evse_security.hpp` interface. This allows you to include your custom implementation of the security related operations according to this interface. If you set this value to nullptr, the internal implementation of the security related operations of libocpp will be used. In this case you need to specify the parameter security_configuration

- security_configuration: this parameter should only be set in case the evse_security parameter is nullptr. It specifies the file paths that are required to set up the internal evse_security implementation. Note that you need to specify bundle files for the CA certificates and directories for the certificates and keys

  The directory layout expected is as follows

  ```bash
  .
  ├── ca
  │   ├── csms
  │   │   └── CSMS_ROOT_CA.pem
  │   ├── cso
  │   │   ├── CPO_CERT_CHAIN.pem
  │   │   ├── CPO_SUB_CA1_LEAF.der
  │   │   ├── CPO_SUB_CA1.pem
  │   │   ├── CPO_SUB_CA2_LEAF.der
  │   │   └── CPO_SUB_CA2.pem
  │   ├── mf
  │   │   └── MF_ROOT_CA.pem
  │   ├── mo
  │   │   ├── INTERMEDIATE_MO_CA_CERTS.pem
  │   │   ├── MO_ROOT_CA.der
  │   │   ├── MO_ROOT_CA.pem
  │   │   ├── MO_SUB_CA1.der
  │   │   ├── MO_SUB_CA1.pem
  │   │   ├── MO_SUB_CA2.der
  │   │   └── MO_SUB_CA2.pem
  │   └── v2g
  │       ├── V2G_ROOT_CA.der
  │       └── V2G_ROOT_CA.pem
  ├── client
  │   ├── csms
  │   │   ├── CPO_CERT_CHAIN.pem
  │   │   ├── CPO_SUB_CA1.key
  │   │   ├── CPO_SUB_CA2.key
  │   │   ├── SECC_LEAF.der
  │   │   ├── SECC_LEAF.key
  │   │   └── SECC_LEAF.pem
  │   ├── cso
  │   │   ├── CPO_CERT_CHAIN.pem
  │   │   ├── CPO_SUB_CA1.key
  │   │   ├── CPO_SUB_CA2.key
  │   │   ├── SECC_LEAF.der
  │   │   ├── SECC_LEAF.key
  │   │   └── SECC_LEAF.pem
  │   └── v2g
  │       └── V2G_ROOT_CA.key
  ```

#### registering callbacks

You can (and in many cases MUST) register a number of callbacks so libocpp can interact with the charger. In EVerest most of this functionality is orchestrated by the "EvseManager" module, but you can also register your own callbacks interacting directly with your chargers software. Following is a list of callbacks that you must register and a few words about their purpose.

TODO: in a future version of libocpp the callbacks will be organised in a struct with optional members emphasizing the required and optional callbacks.

Some general notes: the "connector" parameter of some of the callbacks refers to the connector number as understood in the OCPP 1.6 specification, "0" means the whole charging station, the connectors with EVSEs used for charging cars start at "1".

- register_pause_charging_callback

  this callback is used by libocpp to request pausing of charging, the "connector" parameter tells you which connector/EVSE has to pause charging

- register_resume_charging_callback

  this callback is used by libocpp the request resuming of charging, the "connector" parameter tells you which connector/EVSE can resume charging

- register_stop_transaction_callback

  in EVerest this calls the EvseManagers stop_transaction command which "Stops transactions and cancels charging externally, charging can only be resumed by replugging car. EVSE will also stop transaction automatically e.g. on disconnect, so this only needs to be called if the transaction should end before."
  this will then signal the following events:
  - ChargingFinished
  - TransactionFinished

- register_unlock_connector_callback

  can be used by libocpp to force unlock a connector

- register_reserve_now_callback

  libocpp can use this to reserve a connector, reservation handling is outsourced to a reservation manager in EVerest that implements the reservation interface (EVerest/interfaces/reservation.yaml)

- register_upload_diagnostics_callback

  uses a function (in EVerest provided by the System module) to upload the requested diagnostics file

- register_upload_logs_callback

  uses a function (in EVerest provided by the System module) to upload the requested log file

- register_update_firmware_callback

  uses a function (in EVerest provided by the System module) to perform a firmware update

- register_signed_update_firmware_callback

  uses a function (in EVerest provided by the System module) to perform a signed firmware update

- register_provide_token_callback

  this callback is used in a remote start transaction to provide a token (prevalidated or not) to the authorization system

- register_set_connection_timeout_callback

  used by libocpp to set the authorization or plug in connection timeout in the authorization system based on the "ConnectionTimeout" configuration key

- register_disable_evse_callback

  used to disable the EVSE (ChangeAvailability.req)

- register_enable_evse_callback

  used to enable the EVSE (ChangeAvailability.req)

- register_cancel_reservation_callback

  used to cancel a reservation in the reservation manager (CancelReservation.req)

- register_signal_set_charging_profiles_callback

  used to signal that new charging schedule(s) have been set, you can then use
  get_all_composite_charging_schedules(duration_s) to get the new valid charging schedules

- register_is_reset_allowed_callback

  used to inquire (in EVerest from the System module) if a reset is allowed

- register_reset_callback

  used to perform a reset of the requested type, it is up to the user to properly stop the charge point when this callback is used

- register_connection_state_changed_callback

  used to inform about the connection state to the CSMS (connected = true, disconnected = false)

- register_configuration_key_changed_callback
  used to react on a changed configuration key. This callback is called when the specified configuration key has been changed by the CSMS

#### Functions that need to be triggered from the outside after new information is availble (on_... functions in the charge point API)

- on_log_status_notification(std::int32_t request_id, std::string log_status)

  can be used to notify libocpp of a log status notification

- on_firmware_update_status_notification(std::int32_t request_id, std::string firmware_update_status)

  can be used to notify libocpp of a firmware update status notification

- on_meter_values(std::int32_t connector, const Powermeter& powermeter)

  provides a Powermeter struct to libocpp (for sending meter values during charging sessions or periodically)

- on_max_current_offered(std::int32_t connector, std::int32_t max_current)

  the maximum current offered to the EV on this connector (in ampere)

#### The following functions are triggered depending on different so called "Session Events" from the EvseManager

each of these functions will have a small note what the Session Event was and what it triggers in libocpp

- on_enabled(std::int32_t connector)

  Notifies libocpp that the connector is functional and operational

- on_disabled(std::int32_t connector)

  Notifies libocpp that the connector is disabled

- on_transaction_started

  Notifies libocpp that a transaction at the given connector has started, this means that authorization is available and the car is plugged in.

  Some of its parameters:

  session_id is an internal session_id originating in the EvseManager to keep track of the transaction, this is NOT to be mistaken for the transactionId from the StartTransactionResponse in OCPP!

  id_token is the token with which the transaction was authenticated

  meter_start contains the meter value in Wh for the connector at start of the transaction

  timestamp at the start of the transaction

- on_transaction_stopped

  Notifies libocpp that the transaction on the given connector with the given reason has been stopped.

  Some of its parameters:

  timestamp at the end of the transaction

  energy_wh_import contains the meter value in Wh for the connector at end of the transaction

- on_suspend_charging_ev

  Notifies libocpp that the EV has paused charging

- on_suspend_charging_evse

  Notifies libocpp that the EVSE has paused charging

- on_resume_charging

  Notifies libocpp that charging has resumed

- on_session_started

  this is mostly used for logging and changing the connector state

- on_session_stopped

  this is mostly used for logging and changing the connector state

- on_error

  Notify libocpp of an error

- on_reservation_start

  Notifies libocpp that a reservation has started

- on_reservation_end

  Notifies libocpp that a reservation has ended

#### Authorization

In EVerest authorization is handled by the Auth module and various auth token providers and validators. The OCPP module acts as both a token provider (for pre validated tokens in RemoteStartTransactions) and a token validator (using the authorize requests, or plug & charge)
To use libocpp as a auth token validator (e.g. before starting a transaction) you can call the "authorize_id_token" function of the ChargePoint object.
