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Extension for PHP to interface efficiently with a Controller Area Network (CAN bus) 2.0A / 2.0B

C 65.90% PHP 18.74% M4 15.36%

php php8 php80 php81 can-bus canbus php-canbus php-extension php-extensions canbus-messages

php-canbus's Introduction

PHP-CanBus Extension

PHP-canbus is THE extension for PHP on Linux that allows PHP code to interface efficiently with a Controller Area Network (CAN bus) 2.0A / 2.0B.

Due to the CAN Frames lightweight nature (they consist only of 11 or 29 bit identifier, 0 to 8 data bytes and flags) using methods like parsing shell_exec('candump vcan0 -n 1') output has huge drawbacks - it supports only blocking mode and is really really slow. Performance is often a key aspect as most use-cases of CAN-Bus is in embedded systems. With this extension you can efficiently control your car, elevator or even airplane.

Development and testing was done on Ubuntu 20.04 with VCAN, real world tests performed on Raspberry Pi 4B + MCP2515+TJA1050 module.

Basics

Classes and methods

class CanBus {

    /**
     * CanBus constructor.
     *
     * @param string $interface non-empty string
     */
    public function __construct(string $interface) {}

    /**
     * Initializes CanBus interface and connects to unix sockets
     * If socket was initialized before, it closes previous connection
     *
     * @param bool $blocking Whether interface should be blocking or not
     * @return bool success/failure
     */
    public function init(bool $blocking = true): bool {}

    /**
     * Attempts to read single CanFrame.
     *
     * @return CanFrame|false CanFrame on success, false on failure
     */
    public function read(): CanFrame|false {}
    
    /**
     * Attempts to send single CanFrame.
     *
     * @return bool success/failure
     */
    public function send(CanFrame $frame): bool {}

    /**
     * Generates random CanFrame
     * ID: 0 to 0x7FF
     * Data: 0 to 8 bytes of values in range of 0 to 0xFF (0-255)
     *
     * @return CanFrame
     */
    public function generateRandomFrame(): CanFrame {}
}

class CanFrame {

    /**
     * CanFrame constructor.
     *
     * @param int $index value in range o 0 to 0x7FFFFFFF (CAN 2.0B)
     * @param array $data 0 to 8 bytes of values in range of 0 to 0xFF (0-255)
     */
    public function __construct(int $index, array $data) {}
}

Examples

Listening:

<?php

// Create new CanBus interface object
$canBus = new CanBus('vcan0');

// Initialize interface (connect to unix socket)
if($canBus->init() === false) {
    // Handle error
}

// Read loop
while(true) {
    $frame = $canBus->read();
    if($frame === false) continue;
    
    // Do something with the frame
}

Sending:

<?php

// Create new CanBus interface object
$canBus = new CanBus('vcan0');

// Initialize interface (connect to unix socket)
if($canBus->init() === false) {
    // Handle error
}

// Create new frame
$canFrame = new CanFrame(
    0x204,
    [0x00, 0x02, 0x01]
);

// Send new frame
if($canBus->send($canFrame) === false) {
    // Handle error
}

Testing:

<?php

// Create new CanBus interface object
$canBus = new CanBus('vcan0');

// Generate random frame
$randomCanFrame = $canBus->generateRandomFrame();
var_dump($randomCanFrame);

// Create new frame
$canFrame = new CanFrame(
    0x204, // Id
    [0x00, 0x02, 0x01, 0x00, 0x00, 0x00, 0x00, 0x08] // Data
);
var_dump($canFrame);

Building

Download latest php-dev package (as the time of writing: sudo apt install php8.2-dev).

Then run following commands inside repo directory:

phpize              # configures extension for your PHP version
./configure         # configures extension details
make                # builds extension
make install        # installs extension in your system

Installation

Find out path to your php.ini file by running php -i | grep "Configuration File (php.ini) Path"
- It should be something like /etc/php/8.0/cli
Open php.ini file it in text editor (ex. sudo nano /etc/php/8.0/cli/php.ini)
- As it might be in write-restricted path, use sudo
Find Dynamic Extensions section (around line 900)
If you previously used make install, add line extension=canbus
- Otherwise, add extension=/home/pi/canbus.so where /home/pi/canbus.so is an extension path

TODOs

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php-canbus's Issues

Can-FD

Hey, such a good approach!
Do you plan to add can-fd and long payload support in nearest future? Thank you!

Read Timeout?

Anyway, can you get a timeout on the "read"? For example, if the data on the network stops (for whatever reason), the process sits at the "read command" waiting for data. When used as a service with a watchdog, the watchdog needs to be pinged every 30 seconds, which can not happen when the code is stuck at the ->read function. please help!

Timestamp?

the candump utility provide a timestamp with the NMEa message. Any way to get this timestamp?