MSP430FR5994: Why does my persistent variable in FRAM not get initialized correctly?

uSpark

Part Number: MSP430FR5994

I've defined a persistent variable in my code using the __attribute__((persistent)) directive. In the code I initialize the variable count to zero. It compiles and it's value persists across power loss as I would expect but count's initial value after flashing the device is 0xFF and not zero. It doesn't matter what I set the initial value to in the code it always ends up as 0xFF. I'm using the GCC compiler and MSPFlasher on linux. Any suggestions as to what is causing the initial value to be wrong?

__attribute__ ((persistent)) uint8_t count = 0;

over 7 years ago

0 Cameron LaFollette over 7 years ago

TI__Genius 14875 points

Hi uSpark,

Try

uint8_t __attribute__ ((persistent)) count = 0;

0 Cameron LaFollette over 7 years ago in reply to Cameron LaFollette

TI__Genius 14875 points

Here is example code which should show you how to use data in FRAM.

#include <msp430.h>

#define WRITE_SIZE      128

void FRAMWrite(void);

unsigned char count = 0;
unsigned long data;

#if defined(__TI_COMPILER_VERSION__)
#pragma PERSISTENT(FRAM_write)
unsigned long FRAM_write[WRITE_SIZE] = {0};
#elif defined(__IAR_SYSTEMS_ICC__)
__persistent unsigned long FRAM_write[WRITE_SIZE] = {0};
#elif defined(__GNUC__)
unsigned long __attribute__((persistent)) FRAM_write[WRITE_SIZE] = {0};
#else
#error Compiler not supported!
#endif

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop WDT

    // Configure GPIO
    P1OUT &= ~BIT0;                         // Clear P1.0 output latch for a defined power-on state
    P1DIR |= BIT0;                          // Set P1.0 to output direction

    // Disable the GPIO power-on default high-impedance mode to activate
    // previously configured port settings
    PM5CTL0 &= ~LOCKLPM5;

    // Initialize dummy data
    data = 0x00010001;

    while(1)
    {
        data += 0x00010001;
        FRAMWrite();
        count++;
        if (count > 100)
        {
            P1OUT ^= 0x01;                  // Toggle LED to show 512K bytes
            count = 0;                      // ..have been written
            data = 0x00010001;
        }
    }
}

void FRAMWrite(void)
{
    unsigned int i = 0;

    for (i = 0; i < WRITE_SIZE; i++)
    {
        FRAM_write[i] = data;
    }
}