PHP by default does not offer good COM port support however a PHP extension called Direct IO does offers low level access to IO. We will use this extension for serial port communication. On unix system install the extension using PECL, open a terminal and type. This is a step-by-step guide to using the serial port from a program running under Linux; it was written for the Raspberry Pi serial port with the Raspbian Wheezy distribution.

1. Open Serial Port Linux
2. Php Serial Port Communication Linux Distributions For Laptops
3. Php Serial Port Communication Linux Distributions List
4. Serial Port Communication Program

I am looking for a way to communicate with RS232 serial COM port on windows. I have found 2 solutions on the net, one which is not totally free (introduces deliberate delays on the function) and another with limited capability on Windows. The latter can only write to a COM port on Windows, not read.

I can't look at the code of the first solution since it is compiled into a .dll (makes sense, otherwise people can just edit the delay and not purchase it..) and the second one seems only to use fopen() to open the port and later fwrite() to it for writing, just like one would do to a stream. But apparently freading it returns nothing.

I know it's possible as the first solution did it, although it does require Apache to use php-cgi module instead of php5module.

Any ideas?

7 Answers

Every solution above is either inefficient or too much work.

You can just use the PHP-DIO library (dio_fcntl, dio_open, dio_read, dio_write, dio_seek, ..). It's also in the PHP manual's entry for DIO:

This PECL package isn't available by default. To get it for Windows if you have PHP 5.2.x greater than 5.2.6, you can download it as part of a ZIP:

Both of these links were found in http://www.deveblog.com/index.php/download-pecl-extensions-for-windows/

Here is the build from Linux, just get it and do the phpize/configure/make/make install thing.

I don't know whether it should be used in an Apache session, but go for it.

The easiest way to tackle this would be to write a program in another language (such as C++) and then execute it from your php script with system(). Doing Comm I/O in C++ is trivial.

This assumes you have enough access to the server to configure it to allow the executable to be run by php, etc.

You need to set up the com port using a DOS-like command.

For example, the following line executes the command through php:

To display the results you can use:

Create the resource id:

Write to port:

Read from port:

Maybe someone can help me with the fgets problem. It stacks there for exactly one minute if TO=on, or stacks there forever if TO=off. It seems to be a 'MODE COM' option so maybe a DOS expert can help.

Perhaps instead of fgets, one should use fgetc, since fgets capture through to the newline, while fgetc captures a single character. If a new line isn't encountered, it may block until there is one or until the buffer is flushed. The one minute delay may be windows flushing its buffer on an interval.

Another possible way would be to use the Win32 API through something like w32api_register_function() or ffi and then use serial communications calls to get it to work under Windows.

I had the same problem and already considered writing my own php extension when I came across this solution which is popular with Arduino developers - 'serproxy' (found it at many places, ie. http://www.lspace.nildram.co.uk/freeware.html ) sets up a tcp stack to/from the serial ports and allowed me to use the php socket functions to communicate with it.

Another option is to use an object via ActiveX on windows. There are several, mostly commercial serial objects for COM on windows. You can also expose a .Net based object and register it for COM use as well. Of course, this does presume you have control on the server to register a COM control, as you would need a serial interface.

Another issue is resource contention if this is for use via the Web. If this is for a serial printer, for instance, then a print queue manager would be your best option over direct communication.

If you want to deal with sms using com port then here is the most famous php serial communication class by Rémy Sanchez with google sample code. Here is a thread which includes that topic.

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Open Serial Port Linux

EDIT: I have done some testing with the following script (found here: PHP serial port data return from Arduino). It appears that even using fwrite to /dev/ttyUSB0 outputs my new command plus the last command sent from the device. This makes me think that maybe the serial port was not set up correctly (e.g. might need to use stty to change settings to clear the buffer) or there is something else I need to do (with php) to clear the buffer at /dev/ttyUSB0 before sending a new command. Any help would be appreciated, thanks.

Original question:

I'm using php-serial to communicate with a device via serial port. The device has a function to display all input and output to the serial port on a screen. When I run the following script I can see on the device that the script is taking every command output by the device and repeating it back to the device. I believe this is causing an issue in that I just want to answer 'OK' back to the device, not repeat the output and then say 'OK'. Repeating the same command back first seems to confuse it and then it will not adhere the 'OK' command. I can get around this by outputting 'OK' every 0.1 seconds on a loop, but I would rather read the output from the device and then respond to it accordingly. I don't believe there is anything in my script telling it to do repeat the commands back. Is this an issue with the php-serial class that anyone has experienced? I tried setting $autoflush = false; with no difference.

My script:

Example output on the device screen before my script is run:

Example output on the device screen while my script is running:

1 Answer

install minicom and try before opening the port with:

Php Serial Port Communication Linux Distributions For Laptops

Php Serial Port Communication Linux Distributions List

Serial Port Communication Program

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