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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>Keypad program with encoder</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/16600/keypad-program-with-encoder</link><description> Hi All 
 
I&amp;#39;m looking for a keypad program in c that uses the 74c922 encoder chip. A 3x4 keypad is used. I&amp;#39;m really struggling with this. Can anyone help me? How do you wright the program so that the eprom can tell what keypad has been pressed according</description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: Keypad program with encoder</title><link>https://community.arm.com/thread/96240?ContentTypeID=1</link><pubDate>Thu, 08 Apr 2004 07:07:12 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:a6f54fb6-40a0-4b08-bd79-f95143f44daf</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;i&gt;&amp;quot;But how do impliment the code to tell it to look for the data there?&amp;quot;&lt;/i&gt;&lt;br /&gt;
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You simply examine the state of the DATA AVAILABLE output pin - its sole purpose in life is to tell you when there&amp;#39;s data available.&lt;br /&gt;
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&lt;i&gt;&amp;quot;And do you need a ASCII table as well?&amp;quot;&lt;/i&gt;&lt;br /&gt;
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As I pointed out to you before, the Truth Table on p2 of the data sheet tells you what codes the chip will output for each key in your keypad.&lt;br /&gt;
If you want a different encoding you will, of course, have to do that yourself - or find a different chip that provides the encoding you require!&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Keypad program with encoder</title><link>https://community.arm.com/thread/84463?ContentTypeID=1</link><pubDate>Thu, 08 Apr 2004 03:17:11 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:1169df89-6124-4ef7-88c4-32aaabe45ff3</guid><dc:creator>Free Lunch</dc:creator><description>&lt;p&gt;&amp;quot;But how do impliment the code to tell it to look for the data there?&amp;quot;&lt;br /&gt;
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You don&amp;#39;t need to implement any code yourself. Just crosspost your question to as many newsgroups as possible until someone does it for you.&lt;br /&gt;
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What could be simpler than that?&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Keypad program with encoder</title><link>https://community.arm.com/thread/72409?ContentTypeID=1</link><pubDate>Thu, 08 Apr 2004 02:12:18 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:37eb2161-6c76-4ce4-b302-71ccee8ac731</guid><dc:creator>Ruben Young</dc:creator><description>&lt;p&gt;Yes,&lt;br /&gt;
&lt;br /&gt;
But how do impliment the code to tell it to look for the data there?&lt;br /&gt;
And do you need a ASCII table as well?&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Keypad program with encoder</title><link>https://community.arm.com/thread/41998?ContentTypeID=1</link><pubDate>Wed, 07 Apr 2004 13:24:31 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f018bf4a-bd13-4953-9100-ca46561fd14c</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;Have you read the datasheet for the 74C922?&lt;br /&gt;
&lt;a href="http://www.fairchildsemi.com/ds/MM/MM74C922.pdf" target="_blank"&gt;http://www.fairchildsemi.com/ds/MM/MM74C922.pdf&lt;/a&gt;&lt;br /&gt;
&lt;br /&gt;
You only have to supply 1 control signal to the chip, and receive 1 control signal from the chip, plus the 4 data bits that identify which key was pressed:&lt;br /&gt;
&lt;br /&gt;
The DATA AVAILABLE output pin, surprisingly enough, tells you when there is data available (ie, a keypress) for you to read from the device;&lt;br /&gt;
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The /OUTPUT ENABLE input pin enables the chip&amp;#39;s outputs, so that you can read the data (ie, the keypress);&lt;br /&gt;
&lt;br /&gt;
The A, B, C, D output pins identify which key was pressed, in accordance with the Truth Table shown on p2 of the data sheet.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>