327 lines
18 KiB
HTML
327 lines
18 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="6" MadCap:lastHeight="94" MadCap:lastWidth="853" MadCap:disableMasterStylesheet="true" MadCap:tocPath="" MadCap:InPreviewMode="false" MadCap:PreloadImages="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" lang="en-us" xml:lang="en-us" MadCap:PathToHelpSystem="../../../" MadCap:HelpSystemFileName="Default.xml" MadCap:SearchType="Stem">
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<head><title>I2COUT</title>
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<link href="../../SkinSupport/MadCap.css" rel="stylesheet" />
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<link href="../../Resources/Stylesheets/BSE_Help.css" rel="stylesheet" />
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<script src="../../SkinSupport/MadCapAll.js" type="text/javascript">
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</script>
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</head>
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<body>
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<h1 class="code">I2COUT</h1>
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<div class="ImagePlusCaption">
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<div class="Col2">
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<p>
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<img src="../../graphics/pgm_icon2p.gif" border="0" alt="BS2p icon" title="BS2p icon" />
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<img src="../../graphics/pgm_icon2pe.gif" border="0" alt="BS2pe icon" title="BS2pe icon" />
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<img src="../../graphics/pgm_icon2px.gif" border="0" alt="BS2px icon" title="BS2px icon" />
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</p>
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</div>
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<p style="text-align: right;"><a href="../ExampleTopics/I2cInOutEx.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">I2CIN / I2COUT Example</a>
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</p>
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<p> </p>
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</div>
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<p class="clear"> </p>
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<p> </p>
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<p class="PlainText">Syntax: <span class="keyword_in_text">I2COUT</span> <![CDATA[ ]]><i>Pin</i>,<i> SlaveID</i>,<i><![CDATA[ ]]></i>{<i>Address </i>{\<i>LowAddress</i>},} [<i>OutputData</i>]</p>
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<h2>Function</h2>
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<p class="PlainText">Send data to a device using the I<sup>2</sup>C<sup>®</sup> protocol.
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</p>
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<ul>
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<li value="1"><b><i>Pin</i></b> is a variable/constant/expression (0 or 8) that specifies
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which I/O pins to use. I<sup>2</sup>C devices require two I/O pins to communicate.
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The <i>Pin</i> argument serves a double purpose; specifying the first pin (for
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connection to the device's SDA pin) and, indirectly, the other required pin (for
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connection to the device's SCL pin). See explanation below. Both I/O pins will be
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toggled between output and input mode during the <span class="keyword_in_text">I2COUT</span> command and both
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will be set to input mode by the end of the <span class="keyword_in_text">I2COUT</span> command.</li>
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<li value="2"><b><i>SlaveID</i></b> is a variable/constant/expression (0 - 255) indicating
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the unique ID of the I<sup>2</sup>C device.</li>
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<li value="3"><b><i>Address</i></b> is a variable/constant/expression (0 - 255) indicating
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the desired address within the I<sup>2</sup>C device to send data to. The
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<i>Address</i> argument may be used with the optional <i>LowAddress</i> argument
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to indicate a word-sized address value. Note that some devices like the
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PCF8574 do not require an internal address, so this parameter is optional (BS2p
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firmware 1.3 or later is required to omit the <i>Address</i> parameter).</li>
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<li value="4"><b><i>LowAddress</i></b> is a variable/constant/expression (0 - 255) indicating
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the low-byte of the word-sized address within the I<sup>2</sup>C device to send
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data to. This argument must be used along with the <i>Address</i> argument.</li>
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<li value="5"><b><i>OutputData</i></b> is a list of variables, constants, expressions and
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formatters that tells <span class="keyword_in_text">I2COUT</span> how to format outgoing data. <span class="keyword_in_text">I2COUT</span>can transmit individual or repeating bytes, convert values into decimal,
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hexadecimal or binary text representations, or transmit strings of bytes from
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variable arrays. These actions can be combined in any order in the
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<i>OutputData</i> list.</li>
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</ul>
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<h2>Quick Facts</h2>
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<table width="100%" cellpadding="4" cellspacing="0" border="1">
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<tr bgcolor="#CFCFCF">
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<td align="center"> </td>
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<td align="center" colspan="2">BS2p, BS2pe, and BS2px</td>
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</tr>
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<tr>
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<td width="250" align="center" bgcolor="#CFCFCF">Value of <i>Pin</i></td>
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<td width="40%" align="center">0</td>
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<td width="40%" align="center">8</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">I/O Pin Arrangement</td>
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<td>0: Serial Data (SDA) pin<br></br>1: Serial Clock (SCL) pin</td>
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<td>8: Serial Data (SDA) pin<br></br>9: Serial Clock (SCL) pin</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Transmission Rate</td>
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<td colspan="2">Approximately 81 kBits/sec (BS2p), 45 kBits/sec (BS2pe),
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83 kBits/sec (BS2px) -- not including overhead.</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Special Notes</td>
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<td colspan="2">Both the SDA and SCL pins must have 4.7 kΩ pull-up
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resistors.</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Related Commands</td>
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<td align="center" colspan="2">
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<p colspan="2" align="center"><a href="I2CIN.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">I2CIN</a>
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</p>
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</td>
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</tr>
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</table>
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<h2>Explanation</h2>
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<p class="PlainText">The I<sup>2</sup>C protocol is a form of synchronous serial communication developed
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by Philips Semiconductor. It only requires two I/O pins and both pins can be
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shared between multiple I<sup>2</sup>C devices. The <span class="keyword_in_text">I2COUT</span> command allows
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the BASIC Stamp to send data to an I<sup>2</sup>C device.</p>
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<p class="PlainText">The following is an example of the <span class="keyword_in_text">I2COUT</span> command:</p><pre class="BScode" xml:space="preserve"> I2COUT 0, $A0, 5, [100]</pre>
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<p class="PlainText">This code will transmit a "write" command to an I<sup>2</sup>C device (connected
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to I/O pins 0 and 1), followed by an address of 5 and finally will transmit the
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number 100.</p>
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<p class="PlainText">The example above will write a byte of data to location 5 of a 24LC16B EEPROM from
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Microchip. The figure below shows the proper wiring for this example to work. The
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<i>SlaveID</i> argument ($A0) is both the ID of the chip and the command to write to
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the chip; the 0 means write. The <i>Address</i> argument (5) is the EEPROM location
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to write to.</p>
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<p class="PlainText"><b>Note</b>: The 4.7 kΩ resisters are required for the <span class="keyword_in_text">I2COUT</span>
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command to function properly.</p>
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<center>
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<img src="../../graphics/24lc16_sch.gif" border="0">
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</img>
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</center>
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<p class="PlainText">The <span class="keyword_in_text">I2COUT</span> command's <i>OutputData</i> argument is similar to the
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<span class="keyword_in_text">DEBUG</span> and <span class="keyword_in_text">SEROUT</span> command's <i>OutputData</i> argument. This means
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data can be sent as literal text, ASCII character values, repetitive values,
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decimal, hexadecimal and binary translations and string data as in the examples
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below. (Assume the 24LC16B EEPROM is being used).</p><pre class="BScode" xml:space="preserve">
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value VAR Byte
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Setup:
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value = 65
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Main:
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I2COUT 0, $A0, 0, [value] ' send ASCII character "A"
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I2COUT 0, $A0, 0, [REP value\5] ' send "A" five times, i.e., "AAAAA"
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I2COUT 0, $A0, 0, [DEC value] ' send "6" and "5"
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I2COUT 0, $A0, 0, [HEX value] ' send "4" and "1"
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I2COUT 0, $A0, 0, [BIN value] ' send "1000001"
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END
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</pre>
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<p class="PlainText">The tables below list all the available conversion formatters and special
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formatters available to the <span class="keyword_in_text">I2COUT</span> command. See the <a href="DEBUG.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">DEBUG</a> and <a href="SEROUT.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">SEROUT</a> commands for
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additional information and examples of their use.</p>
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<table width="100%" cellpadding="4" cellspacing="0" border="1">
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<tr bgcolor="#CFCFCF" align="center" valign="top">
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<td width="20%">Conversion Formatter</td>
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<td width="70%">Type of Number</td>
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<td width="10%">Notes</td>
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</tr>
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<tr align="center">
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<td>DEC{1..5}</td>
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<td align="left">Decimal, optionally fixed to 1 - 5 digits</td>
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<td>1</td>
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</tr>
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<tr align="center">
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<td>SDEC{1..5}</td>
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<td align="left">Signed decimal, optionally fixed to 1 - 5 digits</td>
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<td>1,2</td>
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</tr>
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<tr align="center">
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<td>HEX{1..4}</td>
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<td align="left">Hexadecimal, optionally fixed to 1 - 4 digits</td>
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<td>1</td>
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</tr>
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<tr align="center">
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<td>SHEX{1..4}</td>
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<td align="left">Signed hexadecimal, optionally fixed to 1 - 4 digits </td>
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<td>1,2</td>
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</tr>
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<tr align="center">
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<td>IHEX{1..4}</td>
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<td align="left">Indicated hexadecimal, optionally fixed to 1 - 4 digits</td>
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<td>1</td>
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</tr>
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<tr align="center">
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<td>ISHEX{1..4}</td>
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<td align="left">Signed, indicated hexadecimal, optionally fixed to 1 - 4
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digits ($ prefix)</td>
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<td>1,2</td>
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</tr>
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<tr align="center">
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<td>BIN{1..16}</td>
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<td align="left">Binary, optionally fixed to 1 - 16 digits</td>
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<td>1</td>
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</tr>
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<tr align="center">
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<td>SBIN{1..16}</td>
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<td align="left">Signed binary, optionally fixed to 1 - 16 digits</td>
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<td>1,2</td>
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</tr>
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<tr align="center">
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<td>IBIN{1..16}</td>
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<td align="left">Indicated binary, optionally fixed to 1 - 16 digits</td>
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<td>1</td>
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</tr>
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<tr align="center">
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<td>ISBIN{1..16}</td>
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<td align="left">Signed, indicated binary, optionally fixed to 1 - 16 digits</td>
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<td>1,2</td>
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</tr>
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</table>
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<ol>
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<li value="1">Fixed-digit formatters like DEC4 will pad the number with leading 0s if
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necessary; ex: DEC4 65 sends 0065. If a number is larger than the specified
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number of digits, the leading digits will be dropped; ex: DEC4 56422 sends
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6422.</li>
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<li value="2">Signed modifiers work under two's complement rules.</li>
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</ol>
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<p> </p>
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<table width="100%" cellpadding="4" cellspacing="0" border="1">
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<tr bgcolor="#CFCFCF" align="center" valign="top">
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<td width="20%">Special Formatter</td>
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<td width="80%">Action</td>
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</tr>
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<tr>
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<td align="center">?</td>
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<td>Displays "symbol = x' + carriage return; where x is a number. Default
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format is decimal, but may be combined with conversion formatters (ex: BIN
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? x to display "x = binary_number").</td>
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</tr>
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<tr>
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<td align="center">ASC ?</td>
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<td>Displays "symbol = 'x'" + carriage return; where x is an ASCII character.</td>
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</tr>
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<tr>
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<td align="center">STR ByteArray {\L}</td>
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<td>Send character string from an array. The optional \L argument can be used
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to limit the output to L characters, otherwise, characters will be sent up to
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the first byte equal to 0 or the end of RAM space is reached.</td>
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</tr>
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<tr>
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<td align="center">REP Byte\L</td>
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<td>Send a string consisting of Byte repeated L times (ex: REP "X"\10
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sends "XXXXXXXXXX").</td>
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</tr>
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</table>
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<p> </p>
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<p class="PlainText">The I<sup>2</sup>C protocol has a well-defined standard for the information
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passed at the start of each transmission. First of all, any information sent must
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be transmitted in units of one byte (8-bits). The first byte, we call the
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<i>SlaveID</i>, is an 8-bit pattern whose upper 7-bits contain the unique ID of
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the device you wish to communicate with. The lowest bit indicates whether this
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is a write operation (0) or a read operation (1). Here is the <i>SlaveID</i> <![CDATA[ ]]>format:</p>
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<center>
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<table cellpadding="4" cellspacing="0" border="1">
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<tr align="center" bgcolor="#CFCFCF">
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<td width="35">7</td>
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<td width="35">6</td>
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<td width="35">5</td>
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<td width="35">4</td>
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<td width="35">3</td>
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<td width="35">2</td>
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<td width="35">1</td>
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<td width="35">0</td>
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</tr>
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<tr align="center">
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<td>A<sub>6</sub></td>
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<td>A<sub>5</sub></td>
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<td>A<sub>4</sub></td>
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<td>A<sub>3</sub></td>
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<td>A<sub>2</sub></td>
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<td>A<sub>1</sub></td>
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<td>A<sub>0</sub></td>
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<td>R/W</td>
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</tr>
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</table>
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</center>
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<p> </p>
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<p class="PlainText">The second byte, immediately following the <i>SlaveID</i>, is the <i>Address</i>.
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It indicates the 8-bit address (within the device) where the <i>OutputData</i> is
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to be written (the first location if more than one byte is written). Note that
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the <i>Address</i> argument is optional and may be left unspecified for devices
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that don't require an address parameter.</p>
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<p class="PlainText">Some devices require more than eights bits of address. For this case, the optional
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<i>LowAddress</i> argument can be used for the low-byte of the required address.
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When using the <i>LowAddress</i> argument, the <i>Address</i> argument is
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effectively the high-byte of the address value. For example, if the entire
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address value is 2050, use 8 for the <i>Address</i> argument and 2 for the
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<i>LowAddress</i> argument (8 * 256 + 2 = 2050).</p>
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<p class="PlainText">Following the last address byte is the first byte of data. This data byte may
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be transmitted or received by the BASIC Stamp. In the case of the <span class="keyword_in_text">I2COUT</span>
|
|||
|
|
command, this data byte is transmitted by the BASIC Stamp and received by the
|
|||
|
|
device. Additionally, multiple data bytes can follow the address, depending on
|
|||
|
|
the I<sup>2</sup>C device. Note that every device has different limitations
|
|||
|
|
regarding how may contiguous bytes they can receive or transmit in one session.
|
|||
|
|
Be aware of these device limitations and program accordingly.</p>
|
|||
|
|
<p class="PlainText">Every I<sup>2</sup>C transmission session begins with a Start Condition and
|
|||
|
|
ends with a Stop Condition. Additionally, immediately after every byte is
|
|||
|
|
transmitted, an extra clock cycle is used to send or receive an acknowledgment
|
|||
|
|
signal (ACK). All of these operations are automatically taken care of by the
|
|||
|
|
<span class="keyword_in_text">I2CIN</span> command so that you need not be concerned with them. The general
|
|||
|
|
I<sup>2</sup>C transmission format is shown below.</p>
|
|||
|
|
<center>
|
|||
|
|
<img src="../../graphics/i2c_packet.gif" border="0">
|
|||
|
|
</img>
|
|||
|
|
</center>
|
|||
|
|
<p> </p>
|
|||
|
|
<p class="PlainText">Since the <span class="keyword_in_text">I2COUT</span> command is intended for output only, it actually
|
|||
|
|
overrides the "R/W" bit (bit 0) in the <i>SlaveID</i> argument. This is done to
|
|||
|
|
avoid device conflicts should the value be mistyped. Put simply, this means
|
|||
|
|
commands such as:
|
|||
|
|
|
|||
|
|
</p><pre class="BScode" xml:space="preserve"> I2COUT 0, $A0, 10, [0] </pre>
|
|||
|
|
<p class="PlainText">...and:</p><pre class="BScode" xml:space="preserve"> I2COUT 0, $A1, 10, [0]</pre>
|
|||
|
|
<p class="PlainText">...both transmit the same thing ($A0, then 10, then the data). Even though the
|
|||
|
|
<span class="keyword_in_text">I2COUT</span> command really doesn't care what the value of the <i>SlaveID</i>'s
|
|||
|
|
LSB is, it is suggested that you still set it appropriately for clarity.</p>
|
|||
|
|
<p class="PlainText">Also note that the <span class="keyword_in_text">I2COUT</span> command does not support multiple I<sup>2</sup>C
|
|||
|
|
masters and the BASIC Stamp cannot operate as an I<sup>2</sup>C slave device.</p>
|
|||
|
|
<div class="Col2">
|
|||
|
|
<div class="MasterFoot">
|
|||
|
|
<p MadCap:conditions="BSEconditions.BSEWebHelp (Primary)-INCLUDE"><a href="../../HomeTopics/HomePage.htm">Go to Welcome page</a>
|
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</p>
|
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</div>
|
|||
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</div>
|
|||
|
|
<div class="Col2">
|
|||
|
|
<div class="MasterFoot">
|
|||
|
|
<p style="text-align: right;"><span class="ContactInfoProjectName">BASIC Stamp Help</span> <![CDATA[ ]]><span class="ContactInfoVersion#">Version 2.5.4</span> <![CDATA[ ]]></p>
|
|||
|
|
<p style="text-align: right;">Copyright © <span class="ContactInfoCompanyName">Parallax Inc.</span></p>
|
|||
|
|
<p style="text-align: right;"><span class="SystemShortDate">8/8/2012</span>
|
|||
|
|
</p>
|
|||
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</div>
|
|||
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