MSP430FR5969 Question(s)

[Karamel]

Hi,

I am dealing with a problem which is about msp430 launcher's button. I have written this code which is below. When I debug it, P1IN register changes stupidly. (with or without pressing button) I can not read exact value of P1IN.

Why does it behavior like that?

Code: [Select]

#include <msp430.h>

volatile unsigned int i;//to prevent optimization

void main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer
    PM5CTL0 &= ~LOCKLPM5;                   // Disable the GPIO power-on default high-impedance mode
                                            // to activate previously configured port settings
    P1DIR |= 0x01;                          // Set P1.0 to output direction
    P1REN  = 0x00;


    for(;;)
    {


       if(P1IN == 0)
           P1OUT = 0x01;//BIT 0 LED ON
       else
        P1OUT = 0X00;//LED OFF
    }
}

[Nusa]

Remember that those registers are bytes, with 8 bits associated with 8 physical pins. When you set P1REN to 0, you turned off the internal resistors for all 8 of those pins. That means any of those 8 pins set for input are floating (likely producing random values) if they aren't connected to anything. That probably includes your button switch if it doesn't have an external pullup/down.

That also means "if (P1IN == 0)" is actually saying "if ANY of the input pins on P1 are non-zero, return false". I suspect that's not what you wanted.

Similarly setting P1OUT = 0 is turning off all outputs on P1. (And would affect resistor usage on inputs, if resisters were enabled.) Since you only have one pin set for output, you sorta get away with this one right now, but it'll get you in trouble later.

[Karamel]

Code: [Select]

#include <msp430.h>

volatile unsigned int i;//to prevent optimization

void main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer
    PM5CTL0 &= ~LOCKLPM5;                   // Disable the GPIO power-on default high-impedance mode
                                            // to activate previously configured port settings
    P1DIR |= 0x01;                          // Set P1.0 to output direction
    P1REN  = 0xFF;
    P1OUT = 0x00;


    while(1);
}
I changed my code like that, I am, now, debuging and still it changes stupidly when it is on while infinite loop. I try to get button press information from P1.1 and wanna show it on P1.0 pin.

Could you write this code to try on mine board? Maybe, my board has broken down. I don't know.

[Nusa]

But does the single bit you care about change stupidly?

if ((P1IN & 0x02) == 0) // Test BIT 1
    P1OUT |= 0x01; // BIT 0 LED ON
else
    P1OUT &= 0xFE; // BIT 0 LED OFF

[Karamel]

what does mean? P1OUT != 0x01; // BIT 0 LED ON

[Nusa]

Meant |=
Stupid typo....fixed it.

[Karamel]

Code: [Select]

void Delay()
{
    i = 1000;                               // SW Delay
    do i--;
    while(i != 0);
}

int main(void) {
    WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer
    PM5CTL0 &= ~LOCKLPM5;                   // Disable the GPIO power-on default high-impedance mode
                                            // to activate previously configured port settings

   // P4DIR = 0x00;
   // P4REN = 0xFF;
   // P4OUT = 0xFF;

    P1DIR = 0x01;
    P1REN = 0xFF;
    P1OUT = 0xFF;

    while(1)
    {
        while((P1IN & 0x02) == 0) // Test BIT 1
        {
            Delay();
            if((P1IN & 0x02) == 1){
                P1OUT ^= 0x01; // BIT 0 LED ON
            }
        }
    }
}
I can, now, recognize its pressing down but why it doesn't toggle led?

[Karamel]

I solved it like that,

Code: [Select]

    while(1)
    {
        while((P1IN & 0x02) == 0) // Test BIT 1
        {
            Delay();
            while((P1IN & 0x02) == 0);
            Delay();
            P1OUT ^= 0x01; // BIT 0 LED ON
        }
    }