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Modbus硬件控制01——什么是Modbus - 创客硬件开发 - 清泛IT社区，为创新赋能！
...再回复；如果不一样，说明你这个数据在传输的时候出了问题，数据不对的，所以就抛弃了。
2、实战只谈理论大家可能不太明白，下面举一个例子。Modbus-RTU协议一般我们用的最多功能码就是03和06，大部分都是用modbus来查询传...
Grep not as a regular expression
I need to search for a PHP variable $someVar . However, Grep thinks that I am trying to run a regex and is complaining:
6 ...
Why doesn't C# support the return of references?
...rn ref x;
else
return ref y;
}
and then call it with
int a = 123;
int b = 456;
ref int c = ref Max(ref a, ref b);
c += 100;
Console.WriteLine(b); // 556!
I know empirically that it is possible to build a version of C# that supports these features because I have done so. Advanced pr...
How do I (or can I) SELECT DISTINCT on multiple columns?
...would qualify as "distinct" (though looking identical to the human eye):
(123, NULL)
(123, NULL)
Also passes in a unique index and almost anywhere else, since NULL values do not compare equal according to the SQL standard. See:
Create unique constraint with null columns
OTOH, GROUP BY, DISTIN...
How to get all columns' names for all the tables in MySQL?
...
<?php
$table = 'orders';
$query = "SHOW COLUMNS FROM $table";
if($output = mysql_query($query)):
$columns = array();
while($result = mysql_fetch_assoc($output)):
$...
Possibility of duplicate Mongo ObjectId's being generated in two different collections?
...ing in Mongo itself, it is possible to have duplicate _id's generated with PHP in Mongo.
The use-case where this has happened with regularity for me is when I'm looping through a dataset and attempting to inject the data into a collection.
The array that holds the injection data must be explicitl...
Detecting programming language from a snippet
... Might also want to think about where you're splitting the words. In PHP, variables start with $, so maybe you shouldn't be splitting on word bounds, because the $ should stick with the variable. Operators like => and := should be stuck together as a single token, but OTH you probably shoul...
How to submit a form with JavaScript by clicking a link?
... works well without any special function needed. Much easier to write with php as well. <input onclick="this.form.submit()"/>
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curl_exec() always returns false
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+1: Simple and straight trouble-shooting for curl in PHP on curl_exec FALSE return. - Curl Verbose Mode in PHP example
– hakre
Nov 9 '12 at 20:10
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Disable cache for some images
I generate some images using a PHP lib.
13 Answers
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