CODEWITHSUNDEEP
msp430code-composer
Alejandro Herrera
Alejandro Herrera

Reputation: 35

Why is the counter increasing before decreasing?

P1DIR |= 0x01;                          // Set P1.0 (GREEN LED) to output direction
P4DIR |= 0x40;                          // Set P4.6 (RED LED) to output direction
P1OUT |= 0x01;                          // Set GREEN LED on
P4OUT |= 0x40;                          // Set RED LED on

P1REN |= 0x02;                          // enable P1.1 (Pushbutton S2)
P1DIR &= ~0x02;                         // enable read port P1.1 (Pushbutton S2)

P4REN |= 0x20;                          // enable P4.5 (Pushbutton S1)
P4DIR &= ~0x20;                         // enable read port P4.5 (PushButton S1)

volatile unsigned int i;
unsigned int counter = 0;

while(1)
{

    if((P4IN & BIT5)== 0)   // is the pushbutton S2 pressed? (P1.1)
    {
        printf("c= %d\r\n",counter);
        P4OUT ^= 0x40;      // toggle RED LED
        i = 10000;
        do i--;
        while(i != 0);
        counter++;
    }

    if((P1IN & 0x02)==0)
    {
        printf("c= %d\r\n",counter);
        counter--;
    }

    if((P1IN & 0x02)==0)
    {
        P1OUT |= 0x01;      // turn on GREEN LED when pushbutton is pressed
        P4OUT ^= 0x40;      // toggle RED LED
        i = 10000;
        do i--;
        while(i != 0);
    }

    else
    {
        P1OUT &= ~0x01;     // Turns off GREEN LED

        P4OUT ^= 0x40;      // toggle RED LED
        i = 10000;
        do i--;
        while(i != 0);
    }
}
return 0;

}

Hello, my current code here allows me to press down pushbutton S1 and print a statement to the console, while increasing it every time I press it down. It also allows me to decrease it as well every time I press down push button S2. However, my problem is that when I start increasing and want to decrease the value, it will increase once more before decreasing (also happens the other way, if I try to increase after decreasing, it will decrease once more before increasing). I would like to know why that is and what can I do to make it so the program doesn't make that happen and decreases/increases immediately. Thank you

Upvotes: 0

Views: 159

Answers (1)

Eduard Sanz
Eduard Sanz

Reputation: 1

You are printing the counter value before is updated, so you are seeing the value before pushing the button. Try to update counter and then print the result:

if((P4IN & BIT5)== 0)   // is the pushbutton S2 pressed? (P1.1)
{
    counter++;
    printf("c= %d\r\n",counter);
    P4OUT ^= 0x40;      // toggle RED LED
    i = 10000;
    do i--;
    while(i != 0);
}

if((P1IN & 0x02)==0)
{
    counter--;
    printf("c= %d\r\n",counter);
}

Upvotes: 0

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