phogatfirstgitrepo / aioisotp

ISO-TP implemenation for asyncio Python

ISO-TP for asyncio Python

This package implements ISO-TP over CAN as an asyncio transport layer, enabling simultaneous receiving and transmitting messages with any number of connections.

Raw CAN communication uses python-can which offers compatibility for many different CAN interfaces and operating systems.

If SocketCAN ISO-TP module is loaded and Python 3.7+ is used, the transport is delegated to the kernel if possible for better timing performance. Use the 'socketcan' interface. If unsuccessful, raw CAN will be used as fallback.

The isotpserver from can-utils can also be used to bridge a SocketCAN ISO-TP connection over TCP/IP. Use the 'isotpserver' interface and 'host:port' as channel.

Why asynchronous?

Asynchronous programming simplifies some possible use-cases:

• Full duplex receiving and transmitting on a single connection.
• Communicate on multiple connections simultaneously.
• Functional addressing where one request is sent out and all nodes respond, then processing the responses as they arrive.
• Implementing or simulating multiple servers.

No threads need to be handled with all the locking mechanisms required by it.

Installation

Install from PyPI:

$ pip install aioisotp

Documentation

A basic documentation can be built using Sphinx:

$ python setup.py build_sphinx

Quick start

Here is an example of an echo server implemented using a callback based protocol and a client implemented as sequencial reader and writer streams.

import asyncio
import aioisotp


class EchoServer(asyncio.Protocol):

    def connection_made(self, transport):
        self.transport = transport

    def data_received(self, data):
        # Echo back the same data
        self.transport.write(data)


async def main():
    network = aioisotp.ISOTPNetwork('vcan0',
                                    interface='virtual',
                                    receive_own_messages=True)
    with network.open():
        # A server that uses a protocol
        transport, protocol = await network.create_connection(
            EchoServer, 0x1CDADCF9, 0x1CDAF9DC)

        # A client that uses streams
        reader, writer = await network.open_connection(
            0x1CDAF9DC, 0x1CDADCF9)

        writer.write(b'Hello world!')
        response = await reader.read(4095)
        assert response == b'Hello world!'


loop = asyncio.get_event_loop()
loop.run_until_complete(main())

UDS

This package is meant to enable the use of other protocols that require ISO-TP. One of the most common is UDS. A third party library like udsoncan or pyvit can be used to encode and decode payloads.

import aioisotp
import udsoncan

...

reader, writer = await network.open_connection(0x1CDAF9DC, 0x1CDADCF9)

# Construct and send request
request = udsoncan.Request(
    udsoncan.services.ReadDataByIdentifier, data=b'\xF1\x90')
writer.write(request.get_payload())

# Wait for response and decode the payload
payload = await reader.read(4095)
response = udsoncan.Response.from_payload(payload)

print(response)
print(response.data)