MPC5XXX I2C Start signal issue

[satyavasanth]

Hello,

The start signal is not being generated on the I2C bus of MPC5XXX controller. There is no SDA high to low transition observed on the oscilloscope.

I have taken care about configuring the clock, enabling the I2C module, port settings( open drain, weak pull up ) etc that are required in the first place. I could see that the master and transmit bits are set inside the debugger.

Can someone help me find out what could be the reason for not getting a start condition ?

[satyavasanth]

@David : Thank you for the sample code.

The controller is MPC5748G.

I already have these sample codes with me but my problem is something different and may be trivial.

I couldn't see any response from EEPROM slave(AT24256CN).

I had the SCL set up to 100Khz and i am at this stage of code where i am getting stuck up :

When i try to tap the SDA line through the oscilloscope, i don't see any high to low transition on it and this hints me that there is no actual start condition triggered and hence there is no slave address transmission or acknowledgement.

#define CTRL_WRITE  0xA0

while (I2C_0.IBSR.B.IBB==1){}; // while bus is busy, wait

I2C_0.IBCR.B.MS = 1;         // Set transmit and master mode
I2C_0.IBCR.B.TX = 1;         // And generate start condition
//===================START SIGNAL SENT===========================================
I2C_0.IBDR.R = CTRL_WRITE;   // Send byte Control

while ((I2C_0.IBSR.B.IBIF==0)&&(timeout--)){};// Wait until IBIF or a timeout expires
I2C_0.IBSR.B.IBIF=1;                  // Clear the interrupt event flag
while(I2C_0.IBSR.B.RXAK==1){};          // Check for RXAK(ACKNOWLEDGE from Memory)

[davidtosenovjan]

How do you have connected memory device? Do you have pull-up resistors on SCL/SDK lines? Could I see scheme of connection?

[satyavasanth]

Hi,

Its working now, i could transmit. Its a port configuration issue.

But i have still an open point with receive operation.

As i have told you that i am using an ATMEL eeprom chip AT24C256N,

in receive mode, the IBDR starts showing valid data, like 0x1, 0x2..( i have earlier written 10 bytes of data ) but it continuously gets overwritten and then it ends at 0xFF, even before i go and perform a read operation on IBDR. How do i make it to receive byte by byte ? Also my receive operation is being triggered as soon as i set the I2c to receive mode at line number : 7 and not after dummy read operation at Line number : 8. All subsequent read operations are returning only 0xFF.

  1.      I2C_0.IBCR.B.RSTA = 1;     // generate repeated START
  2.     I2C_0.IBDR.R = CTRL_READ;   // Send byte Control
  3.      while ((I2C_0.IBSR.B.IBIF==0)&&(timeout--)){};// Wait until IBIF or a timeout expires
  4.      I2C_0.IBSR.B.IBIF=1;                  // Clear the interrupt event flag
  5.       while(I2C_0.IBSR.B.RXAK==1){};          // Check for RXAK(ACKNOWLEDGE from Memory)  
  6.      //========================CONTROL BYTE SENT======================================
  7.       I2C_0.IBCR.B.TX = 0;    //set for receive
  8.      dummy = I2C_0.IBDR.R;    //initiates next byte data receiving
  9.         while ((I2C_0.IBSR.B.IBIF==0)&&(timeout--)){};  // Wait until IBIF;
10.          I2C_0.IBSR.B.IBIF=1;                        // Clear the interrupt event flag;
11.        while(I2C_0.IBSR.B.RXAK==1){};                // Check for RXAK(ACKNOWLEDGE from Memory)
12.      if(nBytes>1)
13.    {
14.         while(i<(nBytes-1))
15.        {
16.            *(pData+i) = I2C_0.IBDR.R;    //initiates next byte data receiving
17.             while ((I2C_0.IBSR.B.IBIF==0)&&(timeout--)){};  // Wait until IBIF;
18.            I2C_0.IBSR.B.IBIF=1;                        // Clear the interrupt event flag;
19.            while(I2C_0.IBSR.B.RXAK==1){};                // Check for RXAK(ACKNOWLEDGE from Memory)
20.            i++;
21.        }
22.   }

[davidtosenovjan]

You don’t specify used MCU.

Anyway, I could point out following simple I2C driver written by my colleague:

https://community.nxp.com/docs/DOC-330972

Also as example of usage you can see my demo application:

https://community.nxp.com/docs/DOC-331807

Pin settings you may see in main file (function GPIO_Init).