MQTT bridge for Dehne-EVSE

Provides MQTT communication for the Dehne-EVSE (Hardware/Firmware) by translating and bridging the binary protocol to JSON messages sent over MQTT.

It listens on a configurable TCP-port, which multiple Dehne-EVSE charging stations can connect to, and connects to a MQTT-broker of your choice.

Subscribe (listening for MQTT message) and publish (forwarding messages from the EVSE to MQTT) is done on seperate MQTT-topics, to avoid loops. See configuration options.

Build

Install rust and then build:

$ cargo build

Then run:

$ cargo run -- --help
dehneevse_mqtt_bridge 

USAGE:
    dehneevse_mqtt_bridge [OPTIONS]

OPTIONS:
    -a <EVSE_LISTEN_ADDR>                                [default: [::]]
    -c <CONFIGURATION_FILE>                              [default: ./dehneevse_mqtt_bridge.toml]
    -h, --mqtt_host <MQTT_BROKER>                        [default: tcp://localhost:1883]
        --help                                           Print help information
        --mqtt_topic_publish <MQTT_TOPIC_PUBLISH>        [default: from_dehneEVSE]
        --mqtt_topic_subscribe <MQTT_TOPIC_SUBSCRIBE>    [default: to_dehneEVSE]
    -p <EVSE_LISTEN_PORT>                                [default: 9091]

Types of messages

1. new connection

Once a Dehne-EVSE charing station connects to this bridge, it sends its serial-ID (128 bits as hex-string) and firmware-version (8 bits), which is published to MQTT as follows:

{
  "message_type": "new_connection",
  "client_id": "10BA23AB50534D53302E3120FF162332",
  "handshake": {
    "firmware_version": 4
  }
}

After this initial message, the charging station expects to receive some requests (se below) at least every 10 seconds, otherwise it considers the connection to be dead and re-connects. You should send "request_data_collection"-requests at a 5 second interval.

2. notify

As soon as the charging station detects some charge (f.eks cable plugged in), it sends a notification which is published to MQTT as follows:

{
  "message_type": "notify",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

Note that this messages contains no information of what has changes, the server should collect this information by itself via a data readout request (see below).

3. ping request

Sending a ping-request is done by publishing the following message to MQTT:

{
  "message_type": "request_ping",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

The EVSE will then respond with the following MQTT-message:

{
  "message_type": "response_ping",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

4. Data collection

The following request will query all state and measurements from the EVSE:

{
  "message_type": "request_data_collection",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

The EVSE will then respond with the following MQTT-message:

{
  "message_type": "response_collect_data",
  "client_id": "10BA23AB50534D53302E3120FF162332",
  "pwm_percent": 0,
  "contactor_state": false,
  "measurements": {
    "pilot_voltage": "volt_12",
    "proximity_pilot_amps": "no_cable",
    "phase1_millivolts": 0,
    "phase2_millivolts": 0,
    "phase3_millivolts": 0,
    "phase1_milliamps": 0,
    "phase2_milliamps": 0,
    "phase3_milliamps": 0,
    "wifi_rssi": -77,
    "uptime_milliseconds": 42,
    "current_control_pilot_adc": 0,
    "current_proximity_pilot_adc": 0,
    "logging_buffer": ""
  }
}

5. Switching the contactor

Switching on/off the contactor is down via the following MQTT-request:

{
  "message_type": "request_set_contactor_state",
  "client_id": "10BA23AB50534D53302E3120FF162332",
  "contactor_state": true
}

The EVSE will then respond with the following MQTT-message:

{
  "message_type": "response_set_contactor_state",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

6. Setting the charge rate

Setting the allowed charge-rate is done by setting the PWN-duty cycle percentage via the following MQTT-request:

{
  "message_type": "request_set_pwm_percent",
  "client_id": "10BA23AB50534D53302E3120FF162332",
  "pwm_percent": 50
}

The EVSE will then respond with the following MQTT-message:

{
  "message_type": "response_set_pwm_percent",
  "client_id": "10BA23AB50534D53302E3120FF162332"
}

Use 100% for off (no charing allowed). Otherwise, use the mapping between ampere and duty cycle percentage:

• 10% => 6A
• 15% => 10A
• 25% => 16A
• 40% => 25A
• 50% => 32A

Duty cycle = Amps / 0.6

See https://www.ti.com/lit/ug/tidub87/tidub87.pdf