Posted by Jerry Stuckle on 01/16/07 13:35

bloggsfred00@hotmail.com wrote:
> Jerry Stuckle wrote:
>
>>bloggsfred00@hotmail.com wrote:
>>
>>>Jerry Stuckle wrote:
>>>
>>>
>>>>>>I need to read incoming bytes on a COM port but I do not want to have
>>>>>>the script hang if there is nothing to read.
>>>>>>
>>>>>>Is there any way to have PHP interrogate a COM port buffer to see if
>>>>>>there is any content before reading it?
>>>>>>
>>>>>>Any other method to achieve the result would also be welcome.
>>>>>>
>>>>>>Cheers,
>>>>>>
>>>>>>Fred.
>>>>>
>>>>>
>>>>(Top posting fixed)
>>>>hackajar@gmail.com wrote:
>>>>
>>>>>Windows "COM" ports (like com1, com2, etc) do not have a buffer. They
>>>>>are a serial interface that connects directly to the CPU (or CPU bridge
>>>>>I suppose with newer motherboards). You will have to be running in a
>>>>>loop waiting for data on the COM port to get data off it.
>>>>>
>>>>>Think:
>>>>>
>>>>>while(0) {
>>>>> $getData = comportcheckfuntion('com1'); //You would have to write
>>>>>this function or get one off internet
>>>>> if($getData) //do your stuff here
>>>>> else sleep(1); //sleep for a second and then let loop check com port
>>>>>again.
>>>>>}
>>>>>
>>>>>Cheers,
>>>>>Hackajar
>>>>>bloggsfred00@hotmail.com wrote:
>>>>>
>>>>
>>>>
>>>>Incorrect.
>>>>
>>>>First of all, the serial port hardware itself has a 16 byte (or larger)
>>>>buffer built in.
>>>>
>>>>Secondly, the COM port, like all devices in Windows, goes through a
>>>>driver. Your program doesn't talk to the chip itself; it talks to the
>>>>driver (through Windows). This driver has two buffers - a transmit and
>>>>a receive buffer. And IIRC, both are 4K. But I haven't written any COM
>>>>port software since WINNT, so this may have been increased in later
>>>>versions.
>>>>
>>>>But it has not been decreased.
>>>>
>>>>P.S. Please don't top post.
>>>>
>>>>
>>>>--
>>>>==================
>>>>Remove the "x" from my email address
>>>>Jerry Stuckle
>>>>JDS Computer Training Corp.
>>>>jstucklex@attglobal.net
>>>>==================
>>>
>>>
>> > Got it all going using MSComm32.OCX as a COM object using PHP COM
>> > handling. All very simple when you know how....
>> >
>>
>>(Top posting fixed)
>>
>>Yes, you can use the com activex object, and it does help. But it's not
>>necessary.
>>
>>You can even open the COM port as a r/w file if you can accept the
>>default settings (perhaps set up at boot time). No activex object required.
>>
>>P.S. Please don't top post. Thanks.
>>
>>--
>>==================
>>Remove the "x" from my email address
>>Jerry Stuckle
>>JDS Computer Training Corp.
>>jstucklex@attglobal.net
>>==================
>
>
> Sorry about the top post Jerry, but that is the way Google prefers it,
> and the way they make it easy to use. It is actually the way I prefer
> it too, but I am not about to try to sell that to others. Diversity is
> healthy.
>
> I have come to the conclusion that there is no other way to have
> reliable asynchronous comms using PHP on Win32 other than using the
> activex object. So far nobody who says otherwise can say how it can be
> achieved in any sort of detail.
>
> *ALL* other methods that can be implemented with PHP have no method for
> testing the presence of data before a read, and do not return from a
> read when there is no data to read. This generally leads to a lockup in
> the RX side of the comms at some point or other, even with the most
> careful attention to sequences. dio_read() is a case in example.
> fread() cannot be specified with a length less than 1 (e.g. zero=get
> whats there), and therefore falls into the same trap. Perhaps in a
> perfect world with no comms errors ....
>
> I have even tried to implement W32API calls to get the result, but
> there is no reliable way of doing that with PHP before 6 so that went
> the way of the dodo too (trapped in a PHP5 world for now). It is
> returning structures that is the problem.
>
> I have happily implemented MSComm32.ocx with the ultra reliable results
> I needed so the question has become moot for me just now, but if you do
> know of a way (in detail) then I would be most interested for future
> projects.
>
> Cheers,
>
> Fred.
>

(Top posting fixed)

A. Because it upsets the flow of the messages
Q. Why is it so bad?
A. Top Posting
Q. What is the most annoying habit on usenet?

Possibly that's the way you prefer it, but the standards for this group
include bottom posting. You will get more attention when you follow the
standards. Many people just skip over messages which include top posting.

And I highly suggest you get a decent newsreader instead of Google
groups. The vast majority of us here do.

As for how to do it - you can use an ActiveX object, as you indicated.
Or, you can write a small PHP extension which will allow you to interact
with the IOCTL calls. The latter would have the advantage of being more
efficient and an ActiveX object, but you'd have to be able to write a
PHP extension.

As for my other comment - you don't need to use an ActiveX object *if
you can accept the default settings*. In your case you can't, because
you don't want the read to block, so you need to use something like an
ActiveX control or an extension.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

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