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<h1>stxetx.h</h1><a href="stxetx_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment">00001 <span class="comment">/*! \file stxetx.h \brief STX/ETX Packet Protocol Implementation Library. */</span>
00002 <span class="comment">//*****************************************************************************</span>
00003 <span class="comment">//</span>
00004 <span class="comment">// File Name : 'stxetx.h'</span>
00005 <span class="comment">// Title : STX/ETX Packet Protocol Implementation Library</span>
00006 <span class="comment">// Author : Pascal Stang - Copyright (C) 2002-2003</span>
00007 <span class="comment">// Created : 10/9/2002</span>
00008 <span class="comment">// Revised : 02/10/2003</span>
00009 <span class="comment">// Version : 0.1</span>
00010 <span class="comment">// Target MCU : any</span>
00011 <span class="comment">// Editor Tabs : 4</span>
00012 <span class="comment">//</span><span class="comment"></span>
00013 <span class="comment">/// \ingroup general</span>
00014 <span class="comment">/// \defgroup stxetx STX/ETX Packet Protocol Library (stxetx.c)</span>
00015 <span class="comment">/// \code #include "stxetx.h" \endcode</span>
00016 <span class="comment">/// \par Overview</span>
00017 <span class="comment">/// This library provides functions needed to transmit and receive STX/ETX</span>
00018 <span class="comment">/// packets over any interface which can send and receive bytes. STX/ETX is a</span>
00019 <span class="comment">/// simple packet protocol for serial data streams and offers packetization,</span>
00020 <span class="comment">/// type tagging, and checksum protection for user data. Common uses of STX/ETX</span>
00021 <span class="comment">/// might include radio communications were it can improve data reliability over</span>
00022 <span class="comment">/// lossy channels. STX/ETX may also be used effectively anywhere multiple</span>
00023 <span class="comment">/// access to the communication medium is required. The packets can be made</span>
00024 <span class="comment">/// to contain destination addresses or routing information as well as data.</span>
00025 <span class="comment">///</span>
00026 <span class="comment">/// \par STX/ETX Details</span>
00027 <span class="comment">/// STX/ETX is a simple packet protocol that can be wrapped around user</span>
00028 <span class="comment">/// data for one or more of the following reasons:</span>
00029 <span class="comment">/// 1. packetization is needed</span>
00030 <span class="comment">/// - Using packets can be helpful if your data naturally forms </span>
00031 <span class="comment">/// little "bunches" or if different types of data must be sent</span>
00032 <span class="comment">/// over the same channel (a serial cable, for example). If your</span>
00033 <span class="comment">/// data forms "bunches", you can send user data inside STX/ETX</span>
00034 <span class="comment">/// packets with a predetermined structure, like an array of A/D</span>
00035 <span class="comment">/// conversion results. If you need a way to tell the receiver</span>
00036 <span class="comment">/// what kind of data you're sending, you can use the TYPE field</span>
00037 <span class="comment">/// in the STX/ETX packet.</span>
00038 <span class="comment">/// 2. error checking is needed</span>
00039 <span class="comment">/// - STX/ETX packets will add a checksum to your data. This</span>
00040 <span class="comment">/// allows the receiver to verify that data was received correctly</span>
00041 <span class="comment">/// and is error-free. Packets which are corrupted in transmission</span>
00042 <span class="comment">/// and fail the the checksum test are automatically discarded.</span>
00043 <span class="comment">/// Error checking is especially useful when the data transmission</span>
00044 <span class="comment">/// channel is unreliable or noisy (examples: radio, infrared, long</span>
00045 <span class="comment">/// cables, etc)</span>
00046 <span class="comment">/// </span>
00047 <span class="comment">/// STX/ETX packets have the following structure:</span>
00048 <span class="comment">///</span>
00049 <span class="comment">/// [STX][status][type][length][user data...][checksum][ETX]</span>
00050 <span class="comment">///</span>
00051 <span class="comment">/// All fields are 1 byte except for user data which may be 0-255 bytes.</span>
00052 <span class="comment">/// Uppercase fields are constant (STX=0x02, ETX=0x03), lowercase fields</span>
00053 <span class="comment">/// vary. The length field is the number of bytes in the user data area.</span>
00054 <span class="comment">/// The checksum is the 8-bit sum of all bytes between but not including</span>
00055 <span class="comment">/// STX/ETX.</span>
00056 <span class="comment"></span><span class="comment">//</span>
00057 <span class="comment">// This code is distributed under the GNU Public License</span>
00058 <span class="comment">// which can be found at http://www.gnu.org/licenses/gpl.txt</span>
00059 <span class="comment">//</span>
00060 <span class="comment">//*****************************************************************************</span><span class="comment"></span>
00061 <span class="comment">//@{</span>
00062 <span class="comment"></span>
00063 <span class="preprocessor">#ifndef STXETX_H</span>
00064 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_H</span>
00065 <span class="preprocessor"></span>
00066 <span class="preprocessor">#include "<a class="code" href="buffer_8h.html">buffer.h</a>"</span>
00067
00068 <span class="comment">// include project-dependent configuration options</span>
00069 <span class="preprocessor">#include "<a class="code" href="stxetxconf_8h.html">stxetxconf.h</a>"</span>
00070
00071 <span class="comment">// constants</span>
00072 <span class="comment">// packet markers</span>
00073 <span class="preprocessor">#define STX 0x02 // start transmission marker</span>
00074 <span class="preprocessor"></span><span class="preprocessor">#define ETX 0x03 // end transmission marker</span>
00075 <span class="preprocessor"></span><span class="comment">// packet length parameters</span>
00076 <span class="preprocessor">#define STXETX_HEADERLENGTH 4 // number of bytes required for packet header</span>
00077 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_TRAILERLENGTH 2 // number of bytes required for packet trailer</span>
00078 <span class="preprocessor"></span><span class="comment">// packet field offsets</span>
00079 <span class="preprocessor">#define STXETX_STATUSOFFSET 1 // number of bytes from STX to STATUS</span>
00080 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_TYPEOFFSET 2 // number of bytes from STX to TYPE</span>
00081 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_LENGTHOFFSET 3 // number of bytes from STX to LENGTH</span>
00082 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_DATAOFFSET 4 // number of bytes from STX to the data</span>
00083 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_CHECKSUMOFFSET 4 // number of bytes from STX+[length] to CHECKSUM</span>
00084 <span class="preprocessor"></span><span class="preprocessor">#define STXETX_NOETXSTXCHECKSUM 3 // number of bytes used by STX,ETX,CHECKSUM</span>
00085 <span class="preprocessor"></span>
00086
00087 <span class="comment">// function prototypes</span>
00088 <span class="comment"></span>
00089 <span class="comment">//! Initialize STX/ETX packet protocol library</span>
00090 <span class="comment"></span><span class="keywordtype">void</span> <a class="code" href="group__stxetx.html#ga0">stxetxInit</a>(<span class="keywordtype">void</span> (*dataout_func)(<span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> data));
00091 <span class="comment"></span>
00092 <span class="comment">//! Send/Create STX/ETX packet</span>
00093 <span class="comment"></span><span class="keywordtype">void</span> <a class="code" href="group__stxetx.html#ga1">stxetxSend</a>(<span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> status, <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> type, <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> datalength, <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span>* dataptr);
00094 <span class="comment"></span>
00095 <span class="comment">//! Process a buffer containing STX/ETX packets</span>
00096 <span class="comment"></span><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga2">stxetxProcess</a>(<a class="code" href="structstruct__cBuffer.html">cBuffer</a>* rxBuffer);
00097 <span class="comment"></span>
00098 <span class="comment">//! Returns the received packet's status</span>
00099 <span class="comment"></span><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga3">stxetxGetRxPacketStatus</a>(<span class="keywordtype">void</span>);
00100 <span class="comment"></span>
00101 <span class="comment">//! Returns the received packet's type</span>
00102 <span class="comment"></span><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga4">stxetxGetRxPacketType</a>(<span class="keywordtype">void</span>);
00103 <span class="comment"></span>
00104 <span class="comment">//! Returns the received packet's datalength</span>
00105 <span class="comment"></span><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga5">stxetxGetRxPacketDatalength</a>(<span class="keywordtype">void</span>);
00106 <span class="comment"></span>
00107 <span class="comment">//! Returns pointer to the received packet's data</span>
00108 <span class="comment"></span><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span>* <a class="code" href="group__stxetx.html#ga6">stxetxGetRxPacketData</a>(<span class="keywordtype">void</span>);
00109
00110
00111 <span class="preprocessor">#endif</span>
00112 <span class="preprocessor"></span><span class="comment">//@}</span>
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