I2C

I2C is an Interface for serial communication between different devices. Therefore, one device acts as a master, other participants of the I2C-Bus act as slaves. Each slave has it's own, unique slave address. The master can address the slaves via this address.

The Microcontroller offers one I2C-Interface, which is on GPIO32 and GPIO33. GPIO32 can be configured as I2C-SDA-Pin for Datatransmission, GPIO33 can be configured as I2C-SCL-Pin for sending or receiving the Clock-Signal for I2C-operations. The TMS320F28335 can operate in I2C-Master and in I2C-Slave mode. In master mode, the Microcontroller can send data actively, in slave mode, all operations for receiving and sending data are managed via interrupts.

Slave-Address-Length is configured to 7 Bit.
Valid values are from 0x01 to 0x3F. Address 0x00 is used for broadcast to send data to all slaves on I2C-Bus.

For Rx- and Tx-operations, I2CMSG_transmit type can be used by assigning values for slave address, Register-Address-Length, Register-Address-High- and -Low-Byte, Data-Length and Databytes to each object.

In Master Mode, TMS320F28335 provides I2C-operations with 100 Kbit per second with 100 kHz on SCL. The maximal length of databytes per transmission is 16 byte.

When TMS320F28335 is configured as I2C-Slave, Master always has to send 2 Registerbytes and 2 Databytes for successful Tx-communication. Make sure that the exact Register-address of I2C-Slave is used to prevent misconfiguration. For successful Rx-communication, Master has to send two Registerbytes to TMS320F28335 -I2C-Slave. Slave will write the value of requested register to I2C-Bus then.

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Code examples

Configuration as I2C-Master

#include "global_defines.h"                             //Include global_defines.h
#include "system_controls/system_controls.h"            //Include module of system controls
#include "i2c/i2c.h"                                    //Include module of I2C
 
I2CInterface I2C = {GPIO32, GPIO33};                    //Instantiate I2CInterface and assign GPIO32 and GPIO33 to I2C
 
I2CMSG_transmit Example_write1 ={
    0x21,                                               //Slave Address
    0x01,                                               //Register Length in Byte
    0x00,                                               //Register Address High
    0x05,                                               //Register Address Low
    0x03,                                               //Data Length in Byte
    0x61,                                               //Data Byte 0
    0x62,                                               //Data Byte 1
    0x63                                                //Data Byte 2
};
 
I2CMSG_transmit Example_write2 ={
    0x21,                                               //Slave Address
    0x00,                                               //Register Length in Byte
    0x00,                                               //Register Address High
    0x00,                                               //Register Address Low
    0x02,                                               //Data Length in Byte
    0x00                                                //Data
};
 
I2CMSG_transmit Example_read1 ={
    0x21,                                               //Slave Address
    0x02,                                               //Register Length in Byte
    0x68,                                               //Register Address High
    0x44,                                               //Register Address Low
    0x02,                                               //Data Length in Byte
    0x00                                                //Data
};
 
void main(void){
    int result = 0;                                     //Optional: can be used to check return values of functions
    setSystemControls();                                //Call setSystemControls() function
    result = init_I2CMasterMode(I2C);                   //Configures GPIO32 and GPIO33 as I2C SDA and I2C SCL. Returns result of operation      
    result = I2C_writeDataAsMaster(&Example_write1);    //Addresses Slave 0x21 and sends 1 Registerbyte and 3 Databytes to Bus. Returns result of operation     
    Example_write2.Data[0] = 0x61;                      //Setting up data for Example_write2
    Example_write2.Data[1] = 0x62;                      //Setting up data for Example_write2
    result = I2C_writeDataAsMaster(&Example_write2);    //Addresses Slave 0x21 and sends 2 Databytes to Bus. Returns result of operation        
    result = I2C_readDataAsMaster(&Example_read1);      //Addresses Slave 0x21 and asks for data in Register 0x6844. Expects to receive 2 Databytes from Slave. Received Data is stored in Example_read1.Data[]. Returns result of operation            
}

Configuration as I2C-Slave

#include "global_defines.h"                             //Include global_defines.h
#include "system_controls/system_controls.h"            //Include module of system controls
#include "i2c/i2c.h"                                    //Include module of I2C
 
I2CInterface I2C = {GPIO32, GPIO33};                    //Define Interface and assign GPIOs
 
void main(void){
    int result = 0;                                     //Optional: can be used to check return values of functions
    setSystemControls();                                //Call setSystemControls() function
    result = init_I2CSlaveMode(I2C, 0x3);               //Configures GPIO32 and GPIO33 as I2C SDA and I2C SCL. Sets slave adress of Device to 0x3. Returns result of operation              
    while(1){
                                                        //Endless loop
    }
}

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Documented C-Code of module:

I2C

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Detailed description in Technical Reference Manual:

Technical_Reference_Manual