interface msp430g2553 to 24lc512 eeprom using i2c protocol

raj gokhale

Other Parts Discussed in Thread: MSP430G2553

hello ,

i am trying to interface msp430g2553 to 24lc512 eeprom using i2c.i have made a0,a1,a2,wp=gnd,and i am using 2.7k pullups for 100khz operation and supply

voltage given to the eeprom is 3.3v.

form the user guide i came to know that the start and stop bits are automatically cleared once the start/stop signals are generated.but i cant see that is

happening with my code(auto clearing of start and stop bits).

please help with the same..

# include "msp430g2553.h"

#define I2CPORTSEL P1SEL

#define I2CPORTOUT P1OUT

#define I2CPORTREN P1REN

#define I2CPORTDIR P1DIR

#define SDA BIT7

#define SCL BIT6

#define SCL_CLOCK_DIV 160

unsigned char i2cframe[50],read[50],buffer;

unsigned int ptr;

void ini2c();

void bytewrite(unsigned char addr,unsigned int data);

void ackpolling();

void write();

void i2cread();

void randomread(unsigned char Address);

void main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

BCSCTL1 = CALBC1_16MHZ; //Set DCO to 1MHz

DCOCTL = CALDCO_16MHZ;

ini2c(); // Initialize I2C module

__delay_cycles(20000); //Allow 24LC256 to write data

bytewrite(16,28);

ackpolling();

randomread(16);

}

void ini2c ()

{

I2CPORTSEL |= SDA + SCL;

P1SEL2 |= SDA + SCL;

UCB0CTL1 |= UCSWRST;

UCB0CTL0 &= 0X00;

UCB0CTL0 |= UCMST+ UCMODE_3 + UCSYNC;

UCB0CTL1 |= UCSSEL_2 + UCTR + UCSWRST;

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

UCB0BR1 = 0;

UCB0I2CSA=0x50;

UCB0CTL1 &= ~UCSWRST;

IE2 |= UCB0TXIE; //Enable TX interrupt

IE2 |= UCB0RXIE; //Enable RX interrupt

}

void bytewrite(unsigned char addr,unsigned int data)

{

unsigned char addrhigh,addrlow;

addrhigh=addr>>8;

addrlow=addr&0xff;

while (UCB0STAT & UCBUSY);

i2cframe[3]=addrhigh;

i2cframe[2]=addrlow;

i2cframe[1]=data;

ptr=3;

write();

IFG2 |= UCB0TXIFG;

UCB0CTL1 |= UCTXSTT; // start condition generation

// => I2C communication is started

__bis_SR_register(LPM0_bits + GIE); // Enter LPM0 w/ interrupts

UCB0CTL1 |= UCTXSTP; // I2C stop condition

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

}

void write()

{

UCB0CTL1 |= UCTR; // UCTR=1 => Transmit Mode (R/W bit = 0)

IE2 &= ~UCB0RXIE; // disable Receive ready interrupt

IE2 |= UCB0TXIE; // enable Transmit ready interrupt

}

void i2cread()

{

UCB0CTL1 &= ~UCTR; // UCTR=0 => Receive Mode (R/W bit = 1)

IE2 &= ~UCB0TXIE; // disable Transmit ready interrupt

IE2 |= UCB0RXIE; // enable Receive ready interrupt

}

#pragma vector=USCIAB0TX_VECTOR

__interrupt void TX_ISR_I2C(void)

{

if(UCB0TXIFG & IFG2)

{

UCB0TXBUF = i2cframe[ptr];// Load TX buffer

ptr--; // Decrement TX byte counter

if(ptr == 0)

{

while(!(IFG2 & UCB0TXIFG));

IE2 &= ~UCB0TXIE; // disable interrupts.

__bic_SR_register_on_exit(LPM0_bits); // Exit LPM0

}

else if(UCB0RXIFG & IFG2)

{

buffer = UCB0RXBUF; // store received data in buffer

__bic_SR_register_on_exit(LPM0_bits); // Exit LPM0

}

void ackpolling()

{

while (UCB0STAT & UCBUSY);

{

UCB0STAT = 0x00;

UCB0CTL1 |= UCTR;

UCB0CTL1 &= ~UCTXSTT;

UCB0CTL1 |= UCTXSTT;

while(UCB0CTL1 & UCTXSTT)

{

if(!(UCNACKIFG & UCB0STAT)) // Break out if ACK received

break;

}

UCB0CTL1 |= UCTXSTP;

while (UCB0CTL1 & UCTXSTP);

__delay_cycles(500);

}while(UCNACKIFG & UCB0STAT);

}

void randomread(unsigned char Address)

{

unsigned char addrhigh,addrlow;

while (UCB0STAT & UCBUSY);

addrhigh = Address >> 8;

addrlow = Address & 0xFF;

i2cframe[1] = addrhigh;

i2cframe[0] = addrlow;

ptr = 1;

write();

UCB0CTL1 |= UCTXSTT;

__bis_SR_register(LPM0_bits + GIE);

i2cread();

UCB0CTL1 |= UCTXSTT;

while(UCB0CTL1 & UCTXSTT);

UCB0CTL1 |= UCTXSTP;

__bis_SR_register(LPM0_bits + GIE);

while(UCB0CTL1 & UCTXSTP);

}

over 12 years ago

0 raj gokhale over 12 years ago

Prodigy 120 points

Hey guys please tell me why the start and stop bits are not clearing.....

0 Brian Boorman over 12 years ago in reply to raj gokhale

Guru 25210 points

raj gokhale said:
Hey guys please tell me why the start and stop bits are not clearing.....

That's not the way to elicit help. Since the people who help answer questions here are (generally) not TI employees, and we do this out of the goodness of our heart in our own spare time.....

1. Tell us what steps you have taken to debug the problem yourself. What have you tried changing? What exactly are the conditions that cause your issue, etc?

2. Your code is long, not indented, and hard to read. Try attaching the file, not copy-pasting into this forum edit box that doesn't understand tabs.

Generally, you want to make it easier for someone to help you, and to not appear demanding an answer. It's forum etiquette.

0 Jens-Michael Gross over 12 years ago

Guru 227245 points

It can have several reasons, external and internal ones.

Your ISR doesn't check for a NACK (in case the slave doesn't answer). It is called imemdiately (in TX mode) after setting TXSTT, writes the first byte to TXBUF, and then might be never called again when the slave doesn't answer. And main remains dormant.

Also, it is a very bad idea to do any busy-waiting inside the ISR. As you do when waiting for TXIFG. You should just restructure your output count logic and exit LPM on the next interrupt. You can even move setting TXSTP into the ISR then.

Besides this, it is a bit unclear what your problem is. What doesn't clear when and where and how do you check for it? Apparently, STT and STP can't both not clear as your code won't set STP unless three bytes have been sent (whcih means that STT is long cleared).

0 raj gokhale over 12 years ago in reply to Jens-Michael Gross

Prodigy 120 points

thanks Jens-Michael Gross

my problem is the condition while (UCB0CTL1 & UCTXSTP); is not occurring .if i comment this code then the program executes well and also load the txbuf with low addr,high addr, and data to be written on that address.but for getting this this data back to comntroller it is not showing the proper data from the address given .

and i have to set the USCIB0RXFG flag manually unless it wont go in the rx isr as it not setting automatically.there is no prblem with txifg flag.

my question is how could i know that data is been actually written to that eeprom memory location

the code used by me is with reference from the ti sample code for interfacing a msp430 to eeprom.

the url is as folllows

http://www.ti.com/mcu/docs/litabsmultiplefilelist.tsp?sectionId=96&tabId=1502&literatureNumber=slaa208a&docCategoryId=1&familyId=342

0 raj gokhale over 12 years ago in reply to raj gokhale

Prodigy 120 points

in my hardware i am using 10K pullups on SDA and SCL lines and operating SCL at ~100k

0 Jens-Michael Gross over 12 years ago in reply to raj gokhale

Guru 227245 points

raj gokhale said:
my problem is the condition while (UCB0CTL1 & UCTXSTP); is not occurring

YOu mean, you set UCTXSTP and it never clears?

In receive mdoe, there is one condition where this may occur: when you set UCTXSTP while there is already a byte in RXBUF and receiving of th enext byte has begun. Then the bus will stall on teh 7th bit of the next byte until you read RXBUF. And since the bus is stalled, the stop condition isn't sent. You need to read RXBUF first.

What I noticed, after calling I2CInit, you wait for the flash to write data. What data= You haven't written anything yet. Shouldn't you wait (or rahter poll the chip) after you wrote something?
Also, you don't need to set UCTXIFG. It is automatically set in transmit mode when you set UCTXSTT.

raj gokhale said:
and i have to set the USCIB0RXFG flag manually unless it wont go in the rx isr as it not setting automatically

hmmmm, that's strange. You mean RXIFG doesn't get set?
It's possible that the transfer is stalled by the eeprom because it is still busy writing when you start the transfer. What does it do when it is busy? Refuse to answer as if not there? Or does it do clock stretching until done?

However, the code seems to set UCTXSTP as soon as UCTXSTT clears, which is actually before receiving of the first byte has started, so UCB0RXIFG will never be set.

Alsom in your reandom read funciton, you fill the address to I2Cframe[0]and [1] rather than [1] and [2]. [0] is never sent in your TX ISR, so you're only sending one address byte. The eeprom possibly doesn't like this. (well, the way you handle your send buffer and the index into it is a bit strange and confusing anyway, apparently for you too)

0 Udgish Patel over 12 years ago in reply to Jens-Michael Gross

Intellectual 255 points

hi jens -michael,

I read ur reply and i am facing same problem as u mentioned that

Jens-Michael Gross said:

However, the code seems to set UCTXSTP as soon as UCTXSTT clears, which is actually before receiving of the first byte has started, so UCB0RXIFG will never be set.

Alsom in your reandom read funciton, you fill the address to I2Cframe[0]and [1] rather than [1] and [2]. [0] is never sent in your TX ISR, so you're only sending one address byte. The eeprom possibly doesn't like this. (well, the way you handle your send buffer and the index into it is a bit strange and confusing anyway, apparently for you too)

which is the right way to do that can u guide me.

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interface msp430g2553 to 24lc512 eeprom using i2c protocol