Category: สู่เส้นทางดิจิตอล

มีคำถามจากท่านลูกค้าที่เป็นนักศึกษา และผู้สนใจระดับเริ่มต้น ในเรื่องของ UART, TTL, RS232, MAX232 คืออะไร มันเป็นยังไง และ มันสัมพันธ์กันอย่างไร  เพราะการสื่อสารข้อมูลแบบนี้ เป็นที่นิยมใช้กันอย่างมาก และ มีการใช้เชื่อมต่อเพื่อสื่อสารกับอุปกรณ์ต่างๆ มากมาย เช่น การสื่อสารกับคอมพิวเตอร์, RFID, GPS, GSM Module, RF Module ฯลฯ บทความนี้ทีมงานจาก ThaiEasyElec.com จะมาให้คำอธิบาย เพื่อให้เข้าใจและนำไปใช้ได้อย่างถูกต้องครับ

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การต่อ RS232 แบบ Crossover or Null Modem เชื่อม Optimod

เก็บข้อมูลไว้ดู การต่อ RS232 แบบ Crossover or Null Modem  ใช้รีโมทเชื่อม Software กับ Optimod 8400

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When we’re talking communication protocols, a UART, SPI and I2C are the common hardware interfaces people use in microcontroller development.

This article will compare the various interfaces: UART, SPI and I2C and their differences. We will be comparing them with various factors through their protocols, advantages and disadvantages of each interface, etc and we will be providing some examples of how these interfaces are being used in microcontrollers.

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Chrome shows “Translate This Page?” at the translation icon. This may be helpful for first-time users who did not know that that button is there, but showing that every single time is a really stupid design. Users are not idiots; They know that they can press the translation icon if they want translation.

I know I can disable that pop-up in the settings by disabling “Offer to translate pages that aren’t in a language you read”, but then the translation icon is gone from the address bar, and there seems to be no way to use the translation feature. It should be an all-or-nothing feature. For example, I am learning French, so sometimes I want to read the French pages myself (so I do not want the page to be translated), and sometimes I want translation because the page is too difficult.

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Summary: in this tutorial, we will show you how to create an updatable view and update data in the underlying table through the view.

Introduction to MySQL updatable views

In MySQL, views are not only query-able but also updatable. It means that you can use the INSERT or UPDATE statement to insert or update rows of the base table through the updatable view. In addition, you can use DELETE statement to remove rows of the underlying table through the view.

However, to create an updatable view, the SELECT statement that defines the view must not contain any of the following elements:

• Aggregate functions such as MIN, MAX, SUM, AVG, and COUNT.
• DISTINCT
• GROUP BY clause.
• HAVING clause.
• UNION or UNION ALL clause.
• Left join or outer join.
• Subquery in the SELECT clause or in the WHERE clause that refers to the table appeared in the FROM clause.
• Reference to non-updatable view in the FROM clause.
• Reference only to literal values.
• Multiple references to any column of the base table.

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BEGIN TRANSACTION;
INSERT INTO Table2 (<columns>)
SELECT <columns>
FROM Table1
WHERE <condition>;

DELETE FROM Table1
WHERE <condition>;

COMMIT;

In Percona’s managed services, we often receive customer questions on communication failure errors—where customers are faced with intermittent “Got an error reading communication packets” messages. I thought this topic deserved blog post so we can discuss possible reasons for this error, and how to remedy this problem. I hope this will help readers on how to investigate and resolve this problem.

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From the start, FoxPro has always had a wide range of commands and functions for processing text – more than are strictly necessary for a database language. This is a list of some of the more useful commands and functions in Visual FoxPro. Many of them can accept extra optional parameters. Look in the FoxPro Help system for more information.

The distinction between commands and functions is that commands do something whereas functions just return a value to be displayed or used in another command.

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