MSP430 LED 完全不闪烁

Question

I've been trying to turn on the LEDs on my MSP430G2553 and it just doesn't work. I've tried the code examples from TI, the pre-generated code composer studio LED blinking project, and even previous code that worked on an MSP430 from the past. None of them seem to work. What could be the problem? Could it be faulty hardware? Here's my code:

#include  <msp430.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer
  P1DIR |= 0x01;                            // Set P1.0 to output direction

  for (;;)
  {
    volatile unsigned int i;
    volatile unsigned int j;

    P1OUT ^= 0x01;                          // Toggle P1.0 using exclusive-OR

    i = 25000;                              // Delay
    while(i--) {
       j = 2;
       while(j--);
    }
  }
}

Answer 1

Can you try this version (still a polling loop, but let's keep it very basic)?

#include <msp430.h>

int main(void) {
  volatile int i;
  WDTCTL = WDTPW | WDTHOLD;
  P1DIR |= 0x01;
  P1OUT = 0x00;

  for (;;) {
    P1OUT ^= 0x01;
    for (i = 0x6000; i > 0; i--) { };
  }
  return 0;
}

I took this from one of my old examples when I used the MSP430 in 2010...

Answer 2

Try replacing your while loop with __delay_cycles(1000000); .

Compilers can optimize-out empty loops even if the loop variable is marked as volatile .

#include  <msp430.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer
  P1DIR |= 0x01;                            // Set P1.0 to output direction

  for (;;)
  {
    P1OUT ^= 0x01;                          // Toggle P1.0 using exclusive-OR

    __delay_cycles(1000000);
  }
}

Answer 3

I encountered a problem with the MSP430FR5994 dev board where the LEDs wouldn't turn on for the blinky example but they would turn on for the "Out Of Box Experience" project. Comparing the code, I determined that the difference is this line from pmm.c:

//For FRAM devices, at start up, the GPO power-on default
//high-impedance mode needs to be disabled to activate previously
//configured port settings. This can be done by clearing the LOCKLPM5
//bit in PM5CTL0 register
PM5CTL0 &= ~LOCKLPM5;

Putting that at the top of main() seems to fix whatever the issue is and the LEDs behave as expected.

Answer 4

After a reset, all port pins are high-impedance with Schmitt triggers and their module functions disabled to prevent any cross currents. Even if you have made all the necessary GPIO settings, you need to clear LOCKLPM5 bit in the PM5CTL register (described in the I/O Configuration After Reset chapter TI User Guide)

PM5CTL0 &= ~LOCKLPM5;

until then, the I/Os remain in their high-impedance state with Schmitt trigger inputs disabled.