使用 Perl 或 PHP 在 Linux 上通过 USB 读写串行设备

发布于 2024-10-18 04:18:32 字数 1122 浏览 2 评论 0原文

我在 Linux 上读取串行设备时遇到问题。这个问题很奇怪，我无法确定原因。

我正在使用 PHP 打开 /dev/ttyUSB0 文件 并开始根据设备的协议与设备进行通信。很多时候我遇到了PHP脚本等待设备响应的情况。当我并行运行一个 Perl 脚本时，它应该执行相同的操作，它向同一设备发送了一个请求，并且据称在没有得到响应的情况下退出。然后我看到PHP脚本得到了响应（只有在Perl脚本发送请求之后）。

我在尝试用PHP读取Arduino时遇到了类似的问题。 PHP 没有从端口得到响应，但 Arduino IDE 的串行监视器打印了它。

我认为我在这里遗漏了有关 Linux 文件和 USB 端口的重要信息。可能是什么问题？我如何知道哪些程序使用该端口/文件？

    $usb = 'ttyUSB0';        
    `stty -F /dev/$usb 9600`;
    `stty -F /dev/$usb -parity`;
    `stty -F /dev/$usb cs8`;
    `stty -F /dev/$usb -cstopb`;
    $f = fopen("/dev/$usb", "r+");
    if(!$f) {
        echo "error opening file\n";
        exit;
    }

    statusRequest($f);
    sleep(1);
    $c = readPort($f);
    echo "$c\n";

function statusRequest($port) {
    $data = "request";
    fwrite($port, $data);
    fflush($port);
}

function readPort($port) {
    $read = 1;
    $c = '';
    while($read > 0) {
        $bytesr = unpack("h*", fread($port, 1));
        $c .= $bytesr[1];
        //echo $bytesr[1];
        if($bytesr[1] == 'ff') {
            $read = 0;
        }
    }    
    return $c;
}

原文

I'm having a problem reading from a serial device on Linux. The problem is rather weird, and I wasn't able to nail down the causes.

I'm opening the /dev/ttyUSB0 file with PHP and beginning to communicate with the device according to the device's protocol. Many times I encountered a situation where the PHP script waits for the device to respond. When I ran a Perl script in parallel which supposed to do the same it sent a request to the same device, and quit supposedly without getting a response. Then I saw that the PHP script got the response (only after the Perl script sent a request).

I encountered a similar matter when trying to read Arduino with PHP. The PHP got no response from the port, but Arduino IDE's Serial Monitor printed it.

I think I'm missing a crucial thing about Linux files and USB ports here. What might be the problem? How can I tell which programs use the port/file?

    $usb = 'ttyUSB0';        
    `stty -F /dev/$usb 9600`;
    `stty -F /dev/$usb -parity`;
    `stty -F /dev/$usb cs8`;
    `stty -F /dev/$usb -cstopb`;
    $f = fopen("/dev/$usb", "r+");
    if(!$f) {
        echo "error opening file\n";
        exit;
    }

    statusRequest($f);
    sleep(1);
    $c = readPort($f);
    echo "$c\n";

function statusRequest($port) {
    $data = "request";
    fwrite($port, $data);
    fflush($port);
}

function readPort($port) {
    $read = 1;
    $c = '';
    while($read > 0) {
        $bytesr = unpack("h*", fread($port, 1));
        $c .= $bytesr[1];
        //echo $bytesr[1];
        if($bytesr[1] == 'ff') {
            $read = 0;
        }
    }    
    return $c;
}

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