ADS1258EVM + DAC controlled Vref

Dear Chris,
One more question, shoul I apply additional external pullups on i2c bus if I am using evm without mmb0?

Hi Daniel,

Yes! The stand-alone EVM does not have pullup resistors on SDA & SCL (the MMB0 was supplying the pullups resistors).

You may not actually need to add any resistors though...
If I recall correctly, you're using the MSP430F5529. Therefore, you can enable the MSP430's internal GPIO pull-up resistor on SDA, when configured as an input (see PxREN and PxOUT). SCL shouldn't need the pullup resistor, as it will always be configured as an output that you control.

Best Regards,
Chris

Hello Chris,

Yes, I am using F5529. I have run into a bit trouble with I2C :( It is the first time when I am using I2C so sorry for new newbie questions.

I have connected the MSP430F5529 P3.1 to EVM SCL and P3.0 to EVM SDA.  I am using the example shipped with DriverLib called: usci_b_i2c_ex3_masterTxSingle. Here is the following code: 

#include "driverlib.h"

#define SLAVE_ADDRESS 0x4C  // User modification 1

uint8_t transmitData;

void main(void)
{
    //Stop WDT
    WDT_A_hold(WDT_A_BASE);

    //Assign I2C pins to USCI_B0
    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P3,GPIO_PIN0 + GPIO_PIN1); // User modification 2

    //Initialize transmit data packet
    transmitData = 0x01;

    //Initialize Master
    USCI_B_I2C_initMasterParam param = {0};
    param.selectClockSource = USCI_B_I2C_CLOCKSOURCE_SMCLK;
    param.i2cClk = UCS_getSMCLK();
    param.dataRate = USCI_B_I2C_SET_DATA_RATE_100KBPS;
    USCI_B_I2C_initMaster(USCI_B0_BASE, &param);

    //Specify slave address
    USCI_B_I2C_setSlaveAddress(USCI_B0_BASE,SLAVE_ADDRESS);

    //Set in transmit mode
    USCI_B_I2C_setMode(USCI_B0_BASE,USCI_B_I2C_TRANSMIT_MODE);

    //Enable I2C Module to start operations
    USCI_B_I2C_enable(USCI_B0_BASE);

    //Enable TX interrupt
    USCI_B_I2C_clearInterruptFlag(USCI_B0_BASE,USCI_B_I2C_TRANSMIT_INTERRUPT);
    USCI_B_I2C_enableInterrupt(USCI_B0_BASE,USCI_B_I2C_TRANSMIT_INTERRUPT);

    while(1)
    {
        //Send single byte data.
        USCI_B_I2C_masterSendSingleByte(USCI_B0_BASE,transmitData);

        //Delay until transmission completes
        while(USCI_B_I2C_isBusBusy(USCI_B0_BASE))
        {
            ;
        }

        //Delay between each transaction
        __delay_cycles(50);

        //Increment transmit data counter
        transmitData++;
    }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_B0_VECTOR
__interrupt
#elif defined(__GNUC__)
__attribute__((interrupt(USCI_B0_VECTOR)))
#endif
void USCI_B0_ISR(void)
{
    switch(__even_in_range(UCB0IV,12))
    {
    //Vector 12: Transmit buffer empty - TXIF
    case USCI_I2C_UCTXIFG:
    {
        __no_operation();
        break;
    }
    default:  break;
    }
}

I have modified the above code only 2 times as I marked.  Here is the Saleae result:

I am in trouble. The Clock does not seems so good but I dont know why.

I have mentioned my problem in this link but I think you can only help :) 

I think the problem should be here: 

GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P3,GPIO_PIN0 + GPIO_PIN1);

But when I replace it to these:

GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P3,GPIO_PIN0);
GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P3,GPIO_PIN1);

The outcome is worst...

Any idea?

UPDATE: I set the DAC address value, then I can read ACK after my messages.

Hi Daniel,

No problem! Let me dig deeper into this on Monday... I have some hardware that I can try this out on.

Currently, are using pull-up resistors?

Best Regards,
Chris

Hi Daniel,

Great job beating me to the answer!

It turns out I was mistaken in one of my previous posts, the external pullup resistors are required. The internal pullups only work in GPIO mode. See the following thread for more details on this:  

I was able to add pullup resistors to the ADS1258EVM and run your code, the only change I made was to the I2C address:

#define SLAVE_ADDRESS 0x4C

Best Regards,
Chris