MDK-ARM Keil, MDK-ARM Datasheet - Page 90

MDK-ARM

Manufacturer Part Number

MDK-ARM

Description

KIT REALVIEW MCU DEVELOPMENT

Manufacturer

Keil

Type

Compiler and IDEr

Datasheets

1.ULINK2.pdf (8 pages)

2.ULINKPRO.pdf (4 pages)

3.MDK-ARM.pdf (156 pages)

Specifications of MDK-ARM

For Use With/related Products

ARM MCUs

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

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Chapter 4. RL-TCPnet Introduction

Here we want to display temperature values held in a C array controlled by the

application code. We add a script command for each line of JavaScript that is

used to pass the graph coordinates. The fixed graph values are replaced by a %s

for the dynamic data. When the page is loaded, each script line will trigger the

cgi gateway function cgi_func(). A second user defined command is added for

each script line (a to l). Each time the script command triggers, the cgi_func() is

called and we enter case ’m’: of the switch statement. The ASCII value of the

second user defined character is read from the env[] array and we deduct

0x61

This converts from an ASCII character value to a binary value between 0 and 11.

This value is used as an index into the application data array (months[]). The

logged temperature data is then converted into an ASCII string. Finally, the

sprintf() command is used to replace the %s in the HTML code with the

application data value. The result is a graph that displays the dynamic data

logged by the application. Using this approach, you can see that web server

scripting commands in TCPnet allow you to pass dynamic application data to any

embedded object.

Exercise: JavaScript

This exercise demonstrates adding a JavaScript Graph object to a CGI page.

AJAX Support

Using the RL-TCPnet scripting language to pass dynamic data to JavaScript

objects allows you to easily build sophisticated html pages that utilize the

thousands of man hours of development that has gone into many web browsers.

However, there are disadvantages if you are trying to display frequently changing

data. An easy solution is for the user to press the browser’s refresh button or you

can add a refresh tag to the <head> section of the HTML code.

While this works, it is not very satisfactory for two reasons. First, this causes the

whole page to reload, what causes screen flicker and thus is not very satisfactory

for the user. Second, the browser has to download the whole page again, which

is slow and consumes bandwidth. The solution to this problem is to use a group

of interrelated web development techniques called “Asynchronous JavaScript and

XML” or Ajax for short. For our purposes, Ajax is used to isolate the dynamic

data within a group of XML tags. This data is then sent to the browser at an

update rate defined within the html page. This means that the dynamic

application data is sent in a single TCP packet providing a very fast update rate

MDK-ARM Keil, MDK-ARM Datasheet - Page 90

MDK-ARM

Specifications of MDK-ARM

Related parts for MDK-ARM