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<h1>i2csw.c</h1><a href="i2csw_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment">00001 <span class="comment">/*! \file i2csw.c \brief Software I2C interface using port pins. */</span>
00002 <span class="comment">//*****************************************************************************</span>
00003 <span class="comment">//</span>
00004 <span class="comment">// File Name : 'i2csw.c'</span>
00005 <span class="comment">// Title : Software I2C interface using port pins</span>
00006 <span class="comment">// Author : Pascal Stang</span>
00007 <span class="comment">// Created : 11/22/2000</span>
00008 <span class="comment">// Revised : 5/2/2002</span>
00009 <span class="comment">// Version : 1.1</span>
00010 <span class="comment">// Target MCU : Atmel AVR series</span>
00011 <span class="comment">// Editor Tabs : 4</span>
00012 <span class="comment">//</span>
00013 <span class="comment">// This code is distributed under the GNU Public License</span>
00014 <span class="comment">// which can be found at http://www.gnu.org/licenses/gpl.txt</span>
00015 <span class="comment">//</span>
00016 <span class="comment">//*****************************************************************************</span>
00017
00018 <span class="preprocessor">#include <avr/io.h></span>
00019
00020 <span class="preprocessor">#include "<a class="code" href="i2csw_8h.html">i2csw.h</a>"</span>
00021
00022 <span class="comment">// Standard I2C bit rates are:</span>
00023 <span class="comment">// 100KHz for slow speed</span>
00024 <span class="comment">// 400KHz for high speed</span>
00025
00026 <span class="comment">//#define QDEL delay(5) // i2c quarter-bit delay</span>
00027 <span class="comment">//#define HDEL delay(10) // i2c half-bit delay</span>
00028
00029 <span class="comment">// i2c quarter-bit delay</span>
00030 <span class="preprocessor">#define QDEL asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop");</span>
00031 <span class="preprocessor"></span><span class="comment">// i2c half-bit delay</span>
00032 <span class="preprocessor">#define HDEL asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop"); asm volatile("nop");</span>
00033 <span class="preprocessor"></span>
00034 <span class="preprocessor">#define I2C_SDL_LO cbi( SDAPORT, SDA)</span>
00035 <span class="preprocessor"></span><span class="preprocessor">#define I2C_SDL_HI sbi( SDAPORT, SDA)</span>
00036 <span class="preprocessor"></span>
00037 <span class="preprocessor">#define I2C_SCL_LO cbi( SCLPORT, SCL); </span>
00038 <span class="preprocessor"></span><span class="preprocessor">#define I2C_SCL_HI sbi( SCLPORT, SCL); </span>
00039 <span class="preprocessor"></span>
00040 <span class="preprocessor">#define I2C_SCL_TOGGLE HDEL; I2C_SCL_HI; HDEL; I2C_SCL_LO;</span>
00041 <span class="preprocessor"></span><span class="preprocessor">#define I2C_START I2C_SDL_LO; QDEL; I2C_SCL_LO; </span>
00042 <span class="preprocessor"></span><span class="preprocessor">#define I2C_STOP HDEL; I2C_SCL_HI; QDEL; I2C_SDL_HI; HDEL;</span>
00043 <span class="preprocessor"></span>
00044 <span class="comment">/*</span>
00045 <span class="comment">void i2ct(void)</span>
00046 <span class="comment">{</span>
00047 <span class="comment"> HDEL; I2C_SCL_HI; HDEL; I2C_SCL_LO;</span>
00048 <span class="comment">}</span>
00049 <span class="comment"></span>
00050 <span class="comment">void i2cstart(void)</span>
00051 <span class="comment">{</span>
00052 <span class="comment"> I2C_SDL_LO; QDEL; I2C_SCL_LO; </span>
00053 <span class="comment">}</span>
00054 <span class="comment"></span>
00055 <span class="comment">void i2cstop(void)</span>
00056 <span class="comment">{</span>
00057 <span class="comment"> HDEL; I2C_SCL_HI; QDEL; I2C_SDL_HI; HDEL;</span>
00058 <span class="comment">}</span>
00059 <span class="comment"></span>
00060 <span class="comment"></span>
00061 <span class="comment">#define I2C_SCL_TOGGLE i2ct();</span>
00062 <span class="comment">#define I2C_START i2cstart();</span>
00063 <span class="comment">#define I2C_STOP i2cstop(); </span>
00064 <span class="comment">*/</span>
00065
00066 UINT i2cPutbyte(u08 b)
00067 {
00068 <span class="keywordtype">int</span> i;
00069
00070 <span class="keywordflow">for</span> (i=7;i>=0;i--)
00071 {
00072 <span class="keywordflow">if</span> ( b & (1<<i) )
00073 I2C_SDL_HI;
00074 <span class="keywordflow">else</span>
00075 I2C_SDL_LO; <span class="comment">// address bit</span>
00076 I2C_SCL_TOGGLE; <span class="comment">// clock HI, delay, then LO</span>
00077 }
00078
00079 I2C_SDL_HI; <span class="comment">// leave SDL HI</span>
00080 <span class="comment">// added </span>
00081 cbi(SDADDR, SDA); <span class="comment">// change direction to input on SDA line (may not be needed)</span>
00082 HDEL;
00083 I2C_SCL_HI; <span class="comment">// clock back up</span>
00084 b = inb(SDAPIN) & (1<<SDA); <span class="comment">// get the ACK bit</span>
00085
00086 HDEL;
00087 I2C_SCL_LO; <span class="comment">// not really ??</span>
00088 sbi(SDADDR, SDA); <span class="comment">// change direction back to output</span>
00089 HDEL;
00090 <span class="keywordflow">return</span> (b == 0); <span class="comment">// return ACK value</span>
00091 }
00092
00093
00094 u08 i2cGetbyte(UINT last)
00095 {
00096 <span class="keywordtype">int</span> i;
00097 u08 c,b = 0;
00098
00099 I2C_SDL_HI; <span class="comment">// make sure pullups are ativated</span>
00100 cbi(SDADDR, SDA); <span class="comment">// change direction to input on SDA line (may not be needed)</span>
00101
00102 <span class="keywordflow">for</span>(i=7;i>=0;i--)
00103 {
00104 HDEL;
00105 I2C_SCL_HI; <span class="comment">// clock HI</span>
00106 c = inb(SDAPIN) & (1<<SDA);
00107 b <<= 1;
00108 <span class="keywordflow">if</span>(c) b |= 1;
00109 HDEL;
00110 I2C_SCL_LO; <span class="comment">// clock LO</span>
00111 }
00112
00113 sbi(SDADDR, SDA); <span class="comment">// change direction to output on SDA line</span>
00114
00115 <span class="keywordflow">if</span> (last)
00116 I2C_SDL_HI; <span class="comment">// set NAK</span>
00117 <span class="keywordflow">else</span>
00118 I2C_SDL_LO; <span class="comment">// set ACK</span>
00119
00120 I2C_SCL_TOGGLE; <span class="comment">// clock pulse</span>
00121 I2C_SDL_HI; <span class="comment">// leave with SDL HI</span>
00122 <span class="keywordflow">return</span> b; <span class="comment">// return received byte</span>
00123 }
00124
00125
00126 <span class="comment">//************************</span>
00127 <span class="comment">//* I2C public functions *</span>
00128 <span class="comment">//************************</span>
00129 <span class="comment"></span>
00130 <span class="comment">//! Initialize I2C communication</span>
<a name="l00131"></a><a class="code" href="i2csw_8c.html#a11">00131</a> <span class="comment"></span><span class="keywordtype">void</span> <a class="code" href="i2c_8c.html#a10">i2cInit</a>(<span class="keywordtype">void</span>)
00132 {
00133 sbi( SDADDR, SDA); <span class="comment">// set SDA as output</span>
00134 sbi( SCLDDR, SCL); <span class="comment">// set SCL as output</span>
00135 I2C_SDL_HI; <span class="comment">// set I/O state and pull-ups</span>
00136 I2C_SCL_HI; <span class="comment">// set I/O state and pull-ups</span>
00137 }
00138 <span class="comment"></span>
00139 <span class="comment">//! Send a byte sequence on the I2C bus</span>
<a name="l00140"></a><a class="code" href="i2csw_8c.html#a12">00140</a> <span class="comment"></span><span class="keywordtype">void</span> <a class="code" href="i2csw_8c.html#a12">i2cSend</a>(u08 device, u08 subAddr, u08 length, u08 *data)
00141 {
00142 I2C_START; <span class="comment">// do start transition</span>
00143 i2cPutbyte(device); <span class="comment">// send DEVICE address</span>
00144 i2cPutbyte(subAddr); <span class="comment">// and the subaddress</span>
00145
00146 <span class="comment">// send the data</span>
00147 <span class="keywordflow">while</span> (length--)
00148 i2cPutbyte(*data++);
00149
00150 I2C_SDL_LO; <span class="comment">// clear data line and</span>
00151 I2C_STOP; <span class="comment">// send STOP transition</span>
00152 }
00153 <span class="comment"></span>
00154 <span class="comment">//! Retrieve a byte sequence on the I2C bus</span>
<a name="l00155"></a><a class="code" href="i2csw_8c.html#a13">00155</a> <span class="comment"></span><span class="keywordtype">void</span> <a class="code" href="i2csw_8c.html#a13">i2cReceive</a>(u08 device, u08 subAddr, u08 length, u08 *data)
00156 {
00157 <span class="keywordtype">int</span> j = length;
00158 u08 *p = data;
00159
00160 I2C_START; <span class="comment">// do start transition</span>
00161 i2cPutbyte(device); <span class="comment">// send DEVICE address</span>
00162 i2cPutbyte(subAddr); <span class="comment">// and the subaddress</span>
00163 HDEL;
00164 I2C_SCL_HI; <span class="comment">// do a repeated START</span>
00165 I2C_START; <span class="comment">// transition</span>
00166
00167 i2cPutbyte(device | READ); <span class="comment">// resend DEVICE, with READ bit set</span>
00168
00169 <span class="comment">// receive data bytes</span>
00170 <span class="keywordflow">while</span> (j--)
00171 *p++ = i2cGetbyte(j == 0);
00172
00173 I2C_SDL_LO; <span class="comment">// clear data line and</span>
00174 I2C_STOP; <span class="comment">// send STOP transition</span>
00175 }
00176
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