EXI for Python (EXPy)

The project provides a C/C++ to Python interface to the LF Energy EVerest EXI encoding library (libcbv2g).

Overview

EXPy is a Python binding for the EXI (Efficient XML Interchange) format, leveraging the LF Energy EVerest implementation. It enables efficient XML processing in Python applications while maintaining compatibility with C/C++ codebases.

Features

• Executables and libraries for converting EXI bytes to Json strings and vice versa

• Headers for EXI bytes to Json objects and vice versa in C++ projects

• Python class for converting EXI bytes to Json objects and vice versa

• Python module for creating Json payloads for V2G messages

TODO

Implement V2G Specifications

• Implement DIN 70121
• Implement ISO 15118-2
• Implement ISO 15118-20

Add testing for each specification

• Implement DIN 70121 Testing (In Progress -- NOT WORKING)
• Implement ISO 15118-2 Testing
• Implement ISO 15118-20 Testing

Requirements

• Python
• C/C++
• CMake
• Ninja

Installation

git clone --recurse-submodules <giturl>
cd EXPy
make

If you clone the project without the --recurse-submodules flag you can run the following command to initialized the submodules

git submodule update --init --recursive

Usage from CMD

For CMD help output

./build/DINProcessor -h

Encode and decode DIN EXI messages
If no arguement specified for input/outfile, will default to stdin/stdout
MUST use double quotes (") and lower case true/false
Usage:
  ./DINProcessor --[encode/decode]='STRING_OPTIONAL' -i FILE_INPUT -o FILE_OUTPUT
  ./DINProcessor --decode='809a021050908c0c0c0c0c51e000040080'
  ./DINProcessor -e -i input.json -o output.txt
  ./DINProcessor [OPTION...]

  -h, --help                 Show help
  -e, --encode [=arg(=cmd)]  Encode EXI message from JSON to EXI bytes
  -d, --decode [=arg(=cmd)]  Decode EXI message from EXI bytes to JSON
  -i, --input arg            Input file to read JSON or EXI bytes from
  -o, --output arg           Output file to write JSON or EXI bytes to

Encoding

User Input

./build/DINProcessor --encode='{"Body": {"SessionSetupRes": {"EVSEID": {"bytes": [0, 127, 0, 0, 16, 255, 119, 61, 253, 127, 0, 0, 90, 120, 167, 154, 129, 127, 0, 0, 92, 191, 184, 154, 129, 127, 0, 0, 176, 220, 184, 154], "bytesLen": 1}, "ResponseCode": 0, "isUsed": true}}, "Header": {"SessionID": {"bytes": [65, 66, 66, 48, 48, 48, 48, 49], "bytesLen": 8}}}'

./build/DINProcessor --encode --input='inputFile.json'

Program Output

809a021050908c0c0c0c0c51e000040080

Decoding

User Input

./build/DINProcessor --decode='809a021050908c0c0c0c0c51e000040080'

./build/DINProcessor --decode --input='inputFile.txt'

Program Output

{
    "Body": {
        "SessionSetupRes": {
            "EVSEID": {
                "bytes": [
                    0
                ],
                "bytesLen": 1
            },
            "ResponseCode": 0,
            "isUsed": true
        }
    },
    "Header": {
        "SessionID": {
            "bytes": [
                65,
                66,
                66,
                48,
                48,
                48,
                48,
                49
            ],
            "bytesLen": 8
        }
    }
}

Usage from Python

A more comprehensive example is shown in the example.py script. A small snipped of this script is shown below.

Python File

from EXIProcessor import *
import json

# EXI string for PreChargeRequest
exiString = b'809a021050908c0c0c0c0c51514002808142807c0c0c0000'
exiBytes = bytes.fromhex(exiString.decode('utf-8'))

# Json string for SessionSetupRes
jsonString = """
{
    "Body": {
        "SessionSetupRes": {
            "EVSEID": {
                "bytes": [
                    0
                ],
                "bytesLen": 1
            },
            "ResponseCode": 0,
            "isUsed": true
        }
    },
    "Header": {
        "SessionID": {
            "bytes": [
                65,
                66,
                66,
                48,
                48,
                48,
                48,
                49
            ],
            "bytesLen": 8
        }
    }
}"""

# Create instance of EXIProcessor
dinProcessor = EXIProcessor(ProtocolEnum.DIN)

# Decode the EXI bytes
decodedJson = dinProcessor.decode(exiBytes)
print("Decoded result:", json.dumps(decodedJson, indent=4))

# Encode the json string
encodedEXIResult = dinProcessor.encode(json.loads(jsonString))
print("Encoded EXi for SessionSetupRes:", encodedEXIResult.hex())

Program Output

Decoded result: 
{
    "Body": {
        "PreChargeReq": {
            "DC_EVStatus": {
                "EVErrorCode": 0,
                "EVRESSSOC": 10,
                "EVReady": 1
            },
            "EVTargetCurrent": {
                "Multiplier": 0,
                "Unit": 3,
                "Value": 0
            },
            "EVTargetVoltage": {
                "Multiplier": -1,
                "Unit": 5,
                "Value": 4000
            },
            "isUsed": true
        }
    },
    "Header": {
        "SessionID": {
            "bytes": [
                65,
                66,
                66,
                48,
                48,
                48,
                48,
                49
            ],
            "bytesLen": 8
        }
    }
}
Encoded EXI for SessionSetupRes: 809a021050908c0c0c0c0c51e000040080