I2C bus learning--example code

Take the three-axis acceleration sensor MMA7660 as an example:

#define MMA7660_SDA GPIO_Pin_10 // PC10 //IIC data line interface

#define MMA7660_SCL GPIO_Pin_15 // PA15 //IIC clock line interface

#define MMA7660_INT GPIO_Pin_14 // PA14 

  1 /*

  2 *================================================ =========

  3 * Function: IIC bus initialization signal

  4 * Parameters: None

  5 * Function return value: None 

  6 * SDA ---

  7 * |________

  8 * SCL ----------

  9 * |____  

 10 *================================================ =========   

 11 */

 12 void I2C_Start(void)

 13 {

 14 MMA7660_SCL_H;

 15 MMA7660_SDA_H;

 16 Delayus(1);

 17 MMA7660_SDA_L;

 18 Delayus(1);  

 19 } 

 20 

 twenty one /*

 22 *================================================ =========

 23 * Function: IIC bus stop signal

 24 * Parameter: None

 25 * Function return value: None 

 26 * SDA ---------

 27 * ______|

 28 * SCL ---------

 29 * |___

 30 *================================================ =========   

 31 */

 32 void I2C_Stop(void)

 33 {

 34 MMA7660_SCL_H;

 35 MMA7660_SDA_L;

 36 Delayus(1);

 37 MMA7660_SDA_H;

 38 Delayus(1);

 39 }

 40 /*

 41 *================================================ =========

 42 * Function: Receive the ACK signal initiated by the slave to the host.

 43 * Parameter: ACKBIT

 44 *          

 45 * Function return value: MMA_ERROR/MMA_OK   

 46 *================================================ =========   

 47 */

 48 unsigned char I2C_SlaveAck(void)

 49 {

 50 unsigned char ts=0;

 51 MMA7660_SCL_L;

 52 MMA7660_SDA_H;

 53   

 54 MMA_SDA_IOIN(); //SDA is set as input

 55 Delayus(1);

 56 MMA7660_SCL_H;

 57   

 58 while(MMA7660_SDA_D!=0)

 59 {

 60ts++;

 61 if(ts>200)

 62 {

 63 MMA_SDA_IOOUT(); //SDA is set as output

 64 MMA7660_SCL_L;

 65 return MMA_ERROR; //Return error    

 66 }

 67 }

 68 MMA7660_SCL_L;

 69 MMA_SDA_IOOUT(); //SDA is set to output

 70 //MMA7660_SDA_H;

 71 Delayus(1);

 72 return MMA_OK; //Return error      

 73 }

 74 

 75 /*

 76 *================================================ =========

 77 * Function: IIC writes one byte of data

 78 * Parameter: a: One byte of data to be written

 79 * Function return value: None

 80 *================================================ =========   

 81 */

 82 void I2C_WriteByte(unsigned char a) 

 83 {

 84 unsigned char i; 

 85 for(i=0; i<8; i++)

 86 {          

 87 MMA7660_SCL_L;

 88 if((a&0x80)!=0) MMA7660_SDA_H;

 89 else MMA7660_SDA_L;

 90 a <<= 1;

 91 Delayus(1);

 92 MMA7660_SCL_H;

 93 Delayus(1);

 94 }   

 95 MMA7660_SCL_L;  

 96 if(I2C_SlaveAck()==MMA_ERROR) //Wait for the ACK signal from the slave.

 97 {

 98 return ;

 99 }

100 }

101 

102 /*

103 *================================================ =========

104 * Function: IIC reads one byte of data

105 * Parameter: None

106 * Function return value: returns a byte of data read out

107 *================================================ =========   

108 */

109 unsigned char I2C_ReadByte(void)

110 {

111 unsigned char a =0;

112 unsigned char i;

113 MMA_SDA_IOIN(); //SDA is set as input    

114 for(i=0; i<8; i++)

115 {

116 a <<= 1;  

117 MMA7660_SCL_H;

118 Delayus(1);

119 if(MMA7660_SDA_D==1) a |= 0x01;

120 Delayus(1);

121 MMA7660_SCL_L;

122 Delayus(2);       

123 }

124 return a;

125 }

126 

127 /*

128 ************************************************* *********

129 *

130 * MMA7660 related functions

131 *

132 ************************************************* *********

133 */

134 /*

135 *================================================ =========

136 * Function: Write MAA7660 register

137 * Parameters:     

138 * Regs_Addr - Register address

139 * Regs_Data - Register value

140 * Function return value:

141 *================================================ =========   

142 */

143 void MMA7660_WriteReg(unsigned char Regs_Addr, unsigned char Regs_Data) 

144 {  

145 I2C_Start();

146 I2C_WriteByte(MMA7660_DEV_WRITE); //Write the Slave address first and configure it to write mode

147 I2C_WriteByte(Regs_Addr); //Write register address

148 I2C_WriteByte(Regs_Data); //Write register contents

149 I2C_Stop(); //End this IIC process

150 }

151 

152 /*

153 *================================================ =========

154 * Function: Read MAA7660 single byte

155 * Parameters

156 * Regs_Addr - Register address

157 * Function return value: register value

158 *================================================ =========   

159 */

160 unsigned char MMA7660_ReadReg(unsigned char Regs_Addr) 

161 {

162 unsigned char ret;

163    

164 I2C_Start();

165    

166 I2C_WriteByte(MMA7660_DEV_WRITE); //Write the Slave address first and configure it to write mode

167 I2C_WriteByte(Regs_Addr); //Write register address

168    

169 I2C_Start();

170 I2C_WriteByte(MMA7660_DEV_READ); //Write the Slave address and configure it to read mode

171 ret=I2C_ReadByte(); //Read data from the sensor

172 I2C_SlaveAck();

173 I2C_Stop(); //End this IIC process 

174    

175 return ret;

176 

177 }