ArduinoOcpp

OCPP-J 1.6 client for the ESP8266 and the ESP32 (more coming soon)

Reference usage: OpenEVSE

PlatformIO package: ArduinoOcpp

Website: www.arduino-ocpp.com

Full compatibility with the Arduino platform. Need a FreeRTOS version? Please contact me

Make your EVSE ready for OCPP 🚗🔌🔋

You can build an OCPP Charge Point controller using the popular, Wi-Fi enabled microcontrollers ESP8266, ESP32 and comparable. This library allows your EVSE to communicate with an OCPP Central System and to participate in your Charging Network.

✔️ Works with SteVe

✔️ Tested with two further (proprietary) central systems

✔️ Integrated and tested in many charging stations

Features

• handles the OCPP communication with the charging network
• implements the standard OCPP charging process
• provides an API for the integration of the hardware modules of your PCB
• works with any TLS implementation and WebSocket library. E.g.
  • Arduino networking stack: Links2004/arduinoWebSockets, or
  • generic embedded systems: Mongoose Networking Library

For simple chargers, the necessary hardware and internet integration is usually far below 1000 LOCs.

Usage guide

Please take examples/ESP/main.cpp as the starting point for your first project. It is a minimal example which shows how to establish an OCPP connection and how to start and stop charging sessions. In this guide, I give a brief overview of the key concepts.

• To get the library running, you have to install all dependencies (see the list below).

  • In case you use PlatformIO, you can just add matth-x/ArduinoOcpp to your project using the PIO library manager.

• In your project's main file, include ArduinoOcpp.h. This gives you a simple access to all functions.

• Before establishing an OCPP connection you have to ensure that your device has access to a Wi-Fi access point. All debug messages are printed on the standard serial (i.e. Serial.print("debug msg")). To redirect debug messages, please refer to src/ArduinoOcpp/Platform.h.

• To connect to your OCPP Central System, call OCPP_initialize(String OCPP_HOST, uint16_t OCPP_PORT, String OCPP_URL). You need to insert the address parameters according to the configuration of your central system. Internally, the library passes these parameters to the WebSocket object without further alteration.

  • To secure the connection with TLS, you have to configure the WebSocket. Please take examples/SECC/main.cpp as an example.

• In your setup() function, you can add the configuration functions from ArduinoOcpp.h to properly integrate your hardware. All configuration functions are documented in ArduinoOcpp.h. For example, to integrate the energy meter of your EVSE, add

setEnergyActiveImportSampler([]() {
    return yourEVSE_readEnergyMeter();
});

• Add OCPP_loop() to your loop() function.

Sending OCPP operations

There are a couple of OCPP operations you can initialize on your EVSE. For example, to send a Boot Notification, use the function

void bootNotification(const char *chargePointModel, const char *chargePointVendor, OnReceiveConfListener onConf = nullptr, ...)`

In practice, it looks like this:

void setup() {

    ... //other code including the initialization of Wi-Fi and OCPP

    bootNotification("My CP model name", "My company name", [] (JsonObject confMsg) {
        //This callback is executed when the .conf() response from the central system arrives
        Serial.print(F("BootNotification was answered. Central System clock: "));
        Serial.println(confMsg["currentTime"].as<String>()); //"currentTime" is a field of the central system response
        
        //Notify your hardare that the BootNotification.conf() has arrived. E.g.:
        //evseIsBooted = true;
    });
    
    ... //rest of setup() function; executed immediately as bootNotification() is non-blocking
}

The parameters chargePointModel and chargePointVendor are equivalent to the parameters in the Boot Notification as defined by the OCPP specification. The last parameter OnReceiveConfListener onConf is a callback function which the library executes when the central system has processed the operation and the ESP has received the .conf() response. Here you can add your device-specific behavior, e.g. flash a confirmation LED or unlock the connectors. If you don't need it, the last parameter is optional.

For your first EVSE integration, the onReceiveConfListener is probably sufficient. For advanced EVSE projects, the other listeners likely become relevant:

• onAbortListener: will be called whenever the engine stops trying to finish an operation normally which was initiated by this device.

• onTimeoutListener: will be executed when the operation is not answered until the timeout expires. Note that timeouts also trigger the onAbortListener.

• onReceiveErrorListener: will be called when the Central System returns a CallError. Again, each error also triggers the onAbortListener.

The following example shows the correct usage of all listeners.

authorize(idTag, [](JsonObject conf) { 
    //onReceiveConfListener (optional but very likely necessary for your integration)
    successfullyAuthorized = true; //example client code
    ... //further client code, e.g. beginSession(idTag);
}, []() { 
    //onAbortListener (optional)
    Serial.print(F("[EVSE] Could not authorize charging session. Aborted\n")); //flash error light etc.
}, []() { 
    //onTimeoutListener (optional)
    Serial.print(F("[EVSE] Could not authorize charging session. Reason: timeout\n"));
}, [](const char *code, const char *description, JsonObject details) { 
    //onReceiveErrorListener (optional)
    Serial.print(F("[EVSE] Could not authorize charging session. Reason: received OCPP error: "));
    Serial.println(code);
});

Receiving OCPP operations

The library also reacts on CS-initiated operations. You can add your own behavior there too. For example, to flash a LED on receipt of a Set Charging Profile request, use the following function.

setOnSetChargingProfileRequest([] (JsonObject payload) {
    //...
});

You can also process the original payload from the CS using the payload object.

Transaction and Session management

In practice, there are a couple of prerequisites for OCPP-transactions. The library abstracts them into two conditions:

1. The electric connection between the EVSE and EV is established and safe
2. The user is identified, authorized and shows the intention to charge the vehicle

Your hardware integration is fully responsible for Condition (1). To make the OCPP library aware about the safe connection, set a callback function with setConnectorPluggedSampler(std::function<bool()> connectorPlugged). Condition (2) is handled by both the hardware integration and the OCPP library. To make the library aware about Condition (2) use the functions beginSession(const char *idTag) and endSession(). Note that internally, the OCPP library uses the same functions if it receives a RemoteStartTransaction request, or stops a transaction for any reason.

In return, the function bool ocppPermitsCharge() notifies your hardware implementation if the OCPP transaction is engaged and the EVSE can charge the EV ultimately.

Alternatively, you can manage OCPP transactions by yourself using startTransaction(const char *idTag) and stopTransaction().

To get started quickly with or without EVSE hardware, you can flash the sketch in examples/SECC onto your ESP. That example mimics a full OCPP communications controller as it would look like in a real charging station. You can build a charger prototype based on that example or just view the internal state using the device monitor.

Dependencies

• bblanchon/ArduinoJSON (please upgrade to version 6.19.1)
• Links2004/arduinoWebSockets (please upgrade to version 2.3.6)

In case you use PlatformIO, you can copy all dependencies from platformio.ini into your own configuration file. Alternatively, you can install the full library with dependencies by adding matth-x/ArduinoOcpp in the PIO library manager.

Supported operations

Operation name	supported	in progress	not supported
Core profile
Authorize	✔️
BootNotification	✔️
ChangeAvailability	✔️
ChangeConfiguration	✔️
ClearCache	✔️
DataTransfer	✔️
GetConfiguration	✔️
Heartbeat	✔️
MeterValues	✔️
RemoteStartTransaction	✔️
RemoteStopTransaction	✔️
Reset	✔️
StartTransaction	✔️
StatusNotification	✔️
StopTransaction	✔️
UnlockConnector	✔️
Smart charging profile
ClearChargingProfile	✔️
GetCompositeSchedule			✖️
SetChargingProfile	✔️
Remote trigger profile
TriggerMessage	✔️
Firmware management
GetDiagnostics	✔️
DiagnosticsStatusNotification	✔️
FirmwareStatusNotification	✔️
UpdateFirmware	✔️

Next development steps

• introduce proper offline behavior and package loss / fault detection
• handle fragmented input messages correctly
• add support for multiple power connectors
• add support for the ESP32
• reach full compliance to OCPP 1.6 Smart Charging Profile
• integrate Authorization Cache
• get ready for OCPP 2.0.1

Further help

I hope this guide can help you to successfully integrate an OCPP controller into your EVSE. If something needs clarification or if you have a question, please send me a message.

✉️ : matthias A⊤ arduino-ocpp DО⊤ com

If you want professional assistance for your EVSE project, you can contact me as well. I'm looking forward to hearing about your ideas!