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I2C Loopback Not Working

Hector_Tortosa
Intellectual 475 points


Hi,

Lets see if someone can help me with this.


I Can't get the I2c Loopback working..

I intialize the I2C with the following configuration:

    /** - set i2c mode */
    i2cREG1->MDR =   (uint32)((uint32)0U << 15U)            /* nack mode                         */           
                   | (uint32)((uint32)1U << 14U)            /* free running                      */           
                   | (uint32)(0U)                           /* start condition - master only     */    
                   | (uint32)((uint32)0U <<11U)             /* stop condition                    */ 
                   | (uint32)((uint32)0U <<10U)             /* Master/Slave mode                 */ 
                   | (uint32)((uint32)I2C_TRANSMITTER)      /* Transmitter/receiver              */ 
                   | (uint32)((uint32)I2C_10BIT_AMODE)      /* xpanded address                   */ 
                   | (uint32)((uint32)0U << 7U)             /* repeat mode                       */ 
                   | (uint32)((uint32)1U << 6U)             /* digital loop back                  */
                   | (uint32)((uint32)0U << 4U)             /* start byte - master only          */ 
                   | (uint32)(1U << 3U)                     /* free data format                  */ 
                   | (uint32)(I2C_8_BIT);                   /* bit count                         */

But when I look in the registers I can see the "H" in the send buffer (DXR) but the receive (DRR) is empty!

I've tried to force it using 

i2cREG1->DRR = i2cREG1->DXR;

But the DRR keeps being empty...

Im using a RM48L952HDK.

Any idea about why this can be happening?

  • 0
    TI__Expert 4580 points

    Hello:

    We have received your post and we will get back to you soon.

    Regards.

  • 0 in reply to Enrique Lizarraga
    TI__Mastermind 22715 points

    Hi, there.

    You can use the following code snip as an example for run I2C in digital loopback mode.

     while(Count--)
      {
      I2C0_Ptr->DXR_UN.DXR_ST.datatx_B8 = *TxData;  // data to transmit to Select Destination Register
      I2C0_Ptr->MDR_UN.MDR_ST.stt_B1    = 1;            // Start the transmission

      while(delay--);
      delay = 1000;
     
      *RxData = I2C0_Ptr->DRR_UN.DRR_ST.datarx_B8;                    // Read incoming data and store in array 

      *TxData++;
      *RxData++;
      };

    To send data over loopback path, you will need to set the start flag after writing to the transmit data rgister.

    Thanks and regards,

    Zhaohong