I2C 2

This appears to be the same issue as what is posted in http://community.ti.com/forums/p/2924/10916.aspx#10916.

Perhaps we should stick to one thread to work the issue?

I have an ez430_rf2500  and i work with IAR, y try to simulate the examples, the problem is that i can`t see changes in the data and clock lines. I make the conexion betwen the msp430F2274 using 10 k resistors like the examples says, but when i use the oscilloscope to see data i`m only see the Vcc. I try to make some changes like put in the code P3DIR |= 0x0F before P3SEL |= 0x06, i make this so i can see the clock line but it dosn`t work. This are the codes so if you see something let me know.

************************************Master code:

#include "msp430x22x4.h"

unsigned char TXData;

unsigned char TXByteCtr;

void main(void)

{

  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0

  UCB0CTL1 |= UCSWRST;                      // Enable SW reset

  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode

  UCB0CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset

  UCB0BR0 = 12;                             // fSCL = SMCLK/12 = ~100kHz

  UCB0BR1 = 0;

  UCB0I2CSA = 0x48;                         // Slave Address is 048h

  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation

  IE2 |= UCB0TXIE;                          // Enable TX interrupt

  TXData = 0x00;                            // Holds TX data

  while (1)

  {

    TXByteCtr = 1;                          // Load TX byte counter

    while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent

    UCB0CTL1 |= UCTR + UCTXSTT;             // I2C TX, start condition

    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts

                                            // Remain in LPM0 until all data

                                            // is TX'd

    TXData++;                               // Increment data byte

  }

}

//------------------------------------------------------------------------------

// The USCIAB0TX_ISR is structured such that it can be used to transmit any

// number of bytes by pre-loading TXByteCtr with the byte count.

//------------------------------------------------------------------------------

#pragma vector = USCIAB0TX_VECTOR

__interrupt void USCIAB0TX_ISR(void)

{

  if (TXByteCtr)                            // Check TX byte counter

  {

    UCB0TXBUF = TXData;                     // Load TX buffer

    TXByteCtr--;                            // Decrement TX byte counter

  }

  else

  {

    UCB0CTL1 |= UCTXSTP;                    // I2C stop condition

    IFG2 &= ~UCB0TXIFG;                     // Clear USCI_B0 TX int flag

    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0

  }

}

Hi Brandon

i try to do the example program in IAR ( I2C_6_7) that connect two msp430, but when i use the oscilloscope to see the clock and data lines changes i don`t see anything, y read some post that says about put 0x0F before P3DIR but when i do it i`m still can`t see anything, i use the pull up resistors 10k, i`m only see is that but no changes.

Thanks.

Gaston

ok, i did it. It works fine.

Thanks Brandon. 

Gaston

Hi Gaston,

How could you fix the problem? I am having same problem with MSP430F5438.

Would you please share the solution?

Regards,

Mohammadi

Hi,

i don't use the msp430f5438, but in my case (f2274 ), i solvedt putting 1 line of code (see the post of Brandon). Did you use pull up resistors?

Regards

Gastón

Hello. I have the same problem with this bus. Could somebody say if there are more changes than just adding P3DIR = 0x0F before P3SEL |= 0x06 line? I use eX430-RF2500 dev kit, but still no changes. Clock does not apperaed on I2C lines. Pull ups are added to P2 target board pinouts.

Hi Dmetrij,

did you connect one device as master and the other device as slave? Just asking because is very strange your problem, you must add P3DIR |= 0x0F before P3SEL |= 0x06.

Regards

Gastón

Of course I did. First of all i loaded Slave code to one part of eZ430-RF2500 and then to the other I`ve loaded Master code, but still have problem.

Problem is - SDA - LOW and SCL - HIGH. There is my code. And connection below.

//This is the master code.
#include "msp430x22x4.h"

unsigned char TXData;
unsigned char TXByteCtr;

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1DIR |= (1 << 1);
  P1OUT |= (1 << 1);
  P2DIR |= (1 << 1);
  P2SEL |= (1 << 1);                        // SMCLK Output
  P3DIR = 0x0F;
  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
  UCB0CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset
  UCB0BR0 = 12;                             // fSCL = SMCLK/12 = ~100kHz
  UCB0BR1 = 0;
  UCB0I2CSA = 0x48;                         // Slave Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  IE2 |= UCB0TXIE;                          // Enable TX interrupt

  TXData = 0x00;                            // Holds TX data

  while (1)
  {
    TXByteCtr = 1;                          // Load TX byte counter
    while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent
    UCB0CTL1 |= UCTR + UCTXSTT;             // I2C TX, start condition
    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
                                            // Remain in LPM0 until all data
                                            // is TX'd
    TXData++;                               // Increment data byte
  }
}

//------------------------------------------------------------------------------
// The USCIAB0TX_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count.
//------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  if (TXByteCtr)                            // Check TX byte counter
  {
    UCB0TXBUF = TXData;                     // Load TX buffer
    TXByteCtr--;                            // Decrement TX byte counter
  }
  else
  {
    UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
    IFG2 &= ~UCB0TXIFG;                     // Clear USCI_B0 TX int flag
    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
  }
}



////This is the slave code.
//#include "msp430x22x4.h"
//
//volatile unsigned char RXData;
//
//void main(void)
//{
//  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
//  P1DIR |= (1 << 0);
//  P1OUT |= (1 << 0);
//  P2DIR |= (1 << 1);
//  P2SEL |= (1 << 1);                        // SMCLK Output
//  P3DIR = 0x0F;
//  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0
//  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
//  UCB0CTL0 = UCMODE_3 + UCSYNC;             // I2C Slave, synchronous mode
//  UCB0I2COA = 0x48;                         // Own Address is 048h
//  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
//  IE2 |= UCB0RXIE;                          // Enable RX interrupt
//
//  while (1)
//  {
//    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
//    __no_operation();                       // Set breakpoint >>here<< and read
//  }                                         // RXData
//}
//
//// USCI_B0 Data ISR
//#pragma vector = USCIAB0TX_VECTOR
//__interrupt void USCIAB0TX_ISR(void)
//{
//  RXData = UCB0RXBUF;                       // Get RX data
//  __bic_SR_register_on_exit(CPUOFF);        // Exit LPM0
//}

Hello Gaston.... 

   I'm having the exact same problem that you had trying to communicate two MSP430F2274 via I2C. I implemented the examples i2c 6 - 7 and nothing. Both my SDA and SCL lines are low, and the only thing that I see is Vcc. I tried adding the line of code P3DIR |= 0x0F before P3SEL |= 0x06 and still nothing happens. I was wondering what did you do that fixed the issue. I didn't change the code from the example other than adding the P3DIR |= 0x0F line. I tried adding it to both the master and slave programs and also just to the master and still get nothing.

I would appreciate your feedback on this.

Leo

Leo,

        Check the pull up resistors (10k  in the SDA and SCL lines). Are you still having this problem?

Gastón

Hey Gastón.... thanks for replying very quickly. I did fixed it. It turns out that adding the line of code P3DIR |= 0x0F before P3SEL |= 0x06 won't work. Actually adding the line P3DIR |= 0xFF instead of P3DIR |= 0x0F  is what works. I wanted to point that out for future reference if someone else gets stuck trying to get the I2C communication working. I tested it with the examples I2C 6 - 7 (two MSP430F2274) and with one MSP430F2274 as master and an external optical sensor as slave (using this set of USCI-I2C functions).

I hope this helps in the future and thanks again for your reply

Leo

Hi Leo & Gaston,

 Even I am facing the same issue of not able to setup the I2C communication using the sample code of msp430x22x4_uscib0_i2c_06.c and msp430x22x4_uscib0_i2c_07.c. I have the entire message in this thread and followed all the steps suggested above,but still no success.

I tried inserting P3DIR |= 0x0F as well as P3DIR |= 0xFF before P3SEL |= 0x06. But none of them are working. I am getting SCL as HIGH but SDA is LOW

I have used 10k pull resistors for SDA as well as SCL and have common ground. Any ideas what can be done to solve this issue?

Thanks

Girish

Girish,

you have your own board?  ceck for integrity signal. Check the slave address. What msp430 are you using? in case of the msp430f2274 check the errata 

Gastón

girish KAMATH said:

I am getting SCL as HIGH but SDA is LOW
I have used 10k pull resistors for SDA as well as SCL and have common ground.

Hello Jens,

  Thank you for your quick response. Yes, I did try to isolate the master and check if it was giving the SDA and SCL signal. I am getting the Start bit and slave address sent without slave MCU connected.But as soon as I connect the slave MCU,  there is not start bit nor slave address being sent. There is just a spike on  SDA and SCL after 11 micro second and nothing after that.(I2C frequency is set at 100kHz). My professor and I sat to debug this issue and were unsuccessful.  

Also the interrupt when TX buffer is empty is fired only once after the MSP goes to low power mode. I have set the GIE and USB0TXIE enabled. The programs are from TI sample programs which are given in the top of the thread

Thank you,

Girish

Hi Gaston,

I have my own board. What is the integrity signal? The slave address is 48h; it was given in the sample code of TI- msp430x22x4_uscib0_i2c_06.c.

I have MSP430f2274. I checked the errata pdf and still couldn't solve the problem

Thanks,

Girish

girish KAMATH said:

as soon as I connect the slave MCU,  there is not start bit nor slave address being sent.

girish KAMATH said:

Also the interrupt when TX buffer is empty is fired only once after the MSP goes to low power mode. I have set the GIE and USB0TXIE enabled.

Since it worked with the slave disconnected, the slave seems to be the problem, not the MSP and not the MSP firmware.