OCPP support (alpha)

OCPP (Open Charge Point Protocol) is a communication protocol for electric vehicle charging stations. It defines a WebSocket-based RPC communication protocol to manage station and receive status updates.

AnyCable-Go Pro supports OCPP and allows you to connect your charging stations to Ruby or Rails applications and control everything using Action Cable at the backend.

NOTE: Currently, AnyCable-Go Pro supports OCPP v1.6 only. Please, contact us if you need support for other versions.

How it works

• EV charging station connects to AnyCable-Go via WebSocket
• The station sends a BootNotification request to initialize the connection
• AnyCable transforms this request into several AnyCable RPC calls to match the Action Cable interface:
  1. Authenticate -> Connection#connect to authenticate the station.
  2. Command{subscribe} -> OCPPChannel#subscribed to initialize a channel entity to association with this station.
  3. Command{perform} -> OCPPChannel#boot_notification to handle the BootNotification request.
• Subsequent requests from the station are converted into OCPPChannel action calls (e.g., Authorize -> OCPPChannel#authorize, StartTransaction -> OCPPChannel#start_transaction).

AnyCable also takes care of heartbeats and acknowledgment messages (unless you send them manually, see below).

Usage

To enable OCPP support, you need to specify the --ocpp_path flag (or ANYCABLE_OCPP_PATH environment variable) specify the prefix for OCPP connections:

$ anycable-go --ocpp_path=/ocpp

...
INFO 2023-03-28T19:06:58.725Z context=main Handle OCPP v1.6 WebSocket connections at http://localhost:8080/ocpp/{station_id}
...

AnyCable automatically adds the /:station_id part to the path. You can use it to identify the station in your application.

Example Action Cable channel class

Now, to manage EV connections at the Ruby side, you need to create a channel class. Here is an example:

class OCPPChannel < ApplicationCable::Channel
  def subscribed
    # You can subscribe the station to its personal stream to
    # send remote comamnds to it
    # params["sn"] contains the station's serial number
    # (meterSerialNumber from the BootNotification request)
    stream_for "ev/#{params["sn"]}"
  end

  def boot_notification(data)
    # Data contains the following fields:
    #  - id - a unique message ID
    #  - command - an original command name
    #  - payload - a hash with the original request data
    id, payload = data.values_at("id", "payload")

    logger.info "BootNotification: #{payload}"

    # By default, if not ack sent, AnyCable sends the following:
    # [3, <id>, {"status": "Accepted"}]
    #
    # For boot notification response, the "interval" is also added.
  end

  def status_notification(data)
    id, payload = data.values_at("id", "payload")

    logger.info "Status Notification: #{payload}"
  end

  def authorize(data)
    id, payload = data.values_at("id", "payload")

    logger.info "Authorize: idTag — #{payload["idTag"]}"

    # For some actions, you may want to send a custom response.
    transmit_ack(id:, idTagInfo: {status: "Accepted"})
  end

  def start_transaction(data)
    id, payload = data.values_at("id", "payload")

    id_tag, connector_id = payload.values_at("idTag", "connectorId")

    logger.info "StartTransaction: idTag — #{id_tag}, connectorId — #{connector_id}"

    transmit_ack(id:, transactionId: rand(1000), idTagInfo: {status: "Accepted"})
  end

  def stop_transaction(data)
    id, payload = data.values_at("id", "payload")

    id_tag, connector_id, transaction_id = payload.values_at("idTag", "connectorId", "transactionId")

    logger.info "StopTransaction: transcationId - #{transaction_id}, idTag — #{id_tag}"

    transmit_ack(id:, idTagInfo: {status: "Accepted"})
  end

  # These are special methods to handle OCPP errors and acks
  def error(data)
    id, code, message, details = data.values_at("id", "code", "message", "payload")
    logger.error "Error from EV: #{code} — #{message} (#{details})"
  end

  def ack(data)
    logger.info "ACK from EV: #{data["id"]} — #{data.dig("payload", "status")}"
  end

  private

  def transmit_ack(id:, **payload)
    # IMPORTANT: You must use "Ack" as the command for acks,
    # so AnyCable can correctly translate them into OCPP acks.
    transmit({command: :Ack, id:, payload:})
  end
end

Single-action variant

It's possible to handle all OCPP commands with a single #receive method at the channel class. For that, you must configure anycable-go to not use granular actions for OCPP:

anycable-go --ocpp_granular_actions=false

# or

ANYCABLE_OCPP_GRANULAR_ACTIONS=false anycable-go

In your channel class:

class OCPPChannel < ApplicationCable::Channel
  def subscribed
    stream_for "ev/#{params["sn"]}"
  end

  def receive(data)
    id, command, payload = data.values_at("id", "command", "payload")

    logger.info "[#{id}] #{command}: #{payload}"
  end
end

Remote commands

You can send remote commands to stations via Action Cable broadcasts:

OCPPChannel.broadcast_to(
  "ev/#{serial_number}",
  {
    command: "TriggerMessage",
    id: "<uniq_id>",
    payload: {
      requestedMessage: "BootNotification"
    }
  }
)