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P2.7 As Input?

mnpumar

By mnpumar,
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mnpumar

mnpumar 2

Posted
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I'm trying to use P2.7 as an input pin, but it doesn't seem to be working.

 

Here's the code I'm using:

 

int main( void )
{
 // Stop watchdog timer to prevent time out reset
 WDTCTL = WDTPW + WDTHOLD;

 P2OUT = 0;            //P2 is output low
 P2DIR = BIT6 + BIT7; //P2 is output
 P2SEL = 0;            //P2 is digital i/0
 P2REN = 0;            //P2 disable pullup resistors */

 int i = 1;


 for(;{  //Digital Input
   while (P2IN & BIT7);    //wait for P1.7 to go low (buttion is pressed)
   Display(i);                 //display
   while (!(P2IN & BIT7)); //wait for P1.7 to go high (button is released)
   i = i + 1;              //increase counter
   if (i > 12) i = 0;       //maximum display is 12
 }
}

 

Whole code is here if necessary:

 

#include "io430.h"

void delay(unsigned int n){
 while (n > 0)
   n--;
}

void TurnON(unsigned x, unsigned y)
{
 unsigned YBITS[5] = {BIT0, BIT1, BIT2, BIT3, BIT4};
 unsigned XBITS[3] = {BIT5, BIT6, BIT7};

 P1OUT &= ~YBITS[y]; 
 P1SEL &= ~YBITS[y]; 
 P1DIR |= YBITS[y];  
 P1OUT |= YBITS[y]; 

 if(x < 3)
 {
   P1OUT &= ~XBITS[x]; 
   P1SEL &= ~XBITS[x]; 
   P1DIR |= XBITS[x];  
   P1OUT |= XBITS[x]; 
 }else
 {
   P2OUT &= ~BIT6; 
   P2SEL &= ~BIT6; 
   P2DIR |= BIT6;  
   P2OUT |= BIT6;  
 }
}

void TurnOFF(unsigned x, unsigned y)
{
 unsigned YBITS[5] = {BIT0, BIT1, BIT2, BIT3, BIT4};
 unsigned XBITS[3] = {BIT5, BIT6, BIT7};

 P1OUT &= ~YBITS[y]; 

 if(x < 3)
 {
   P1OUT &= ~XBITS[x]; 
 }else
 {
   P2OUT &= ~BIT6; 
 }
}

void Display(unsigned number)
{
 if(number == 1)
 {
   TurnON(3,0);
   TurnOFF(3,0);
   TurnON(3,1);
   TurnOFF(3,1);
   TurnON(3,2);
   TurnOFF(3,2);
   TurnON(3,3);
   TurnOFF(3,3);
   TurnON(3,4);
   TurnOFF(3,4);
 }
 if(number == 2)
 {
   TurnON(1,0);
   TurnOFF(1,0);
   TurnON(2,0);
   TurnOFF(2,0);
   TurnON(3,0);
   TurnOFF(3,0);
   TurnON(3,1);
   TurnOFF(3,1);

   TurnON(3,2);
   TurnOFF(3,2);
   TurnON(2,3);
   TurnOFF(2,3);
   TurnON(2,2);
   TurnOFF(2,2);
   TurnON(1,2);
   TurnOFF(1,2);

   TurnON(1,3);
   TurnOFF(1,3);
   TurnON(1,4);
   TurnOFF(1,4);
   TurnON(2,4);
   TurnOFF(2,4);
   TurnON(3,4);
   TurnOFF(3,4);  
 }
 else if(number == 3)
 {
   Display(1);
   TurnON(1,0);
   TurnOFF(1,0);
   TurnON(2,0);
   TurnOFF(2,0);

   TurnON(2,3);
   TurnOFF(2,3);
   TurnON(2,2);
   TurnOFF(2,2);
   TurnON(1,2);
   TurnOFF(1,2);  

   TurnON(1,4);
   TurnOFF(1,4);
   TurnON(2,4);
   TurnOFF(2,4);
 }
 else if(number == 4)
 {
   Display(1);
   TurnON(1,0);
   TurnOFF(1,0);
   TurnON(3,0);
   TurnOFF(3,0);
   TurnON(1,1);
   TurnOFF(1,1);
   TurnON(1,2);
   TurnOFF(1,2);
   TurnON(2,2);
   TurnOFF(2,2);
 }
 else if(number == 5)
 {
   TurnON(1,0);
   TurnOFF(1,0);
   TurnON(2,0);
   TurnOFF(2,0);
   TurnON(3,0);
   TurnOFF(3,0);
   TurnON(1,1);
   TurnOFF(1,1);

   TurnON(2,2);
   TurnOFF(2,2);
   TurnON(1,2);
   TurnOFF(1,2);
   TurnON(3,2);
   TurnOFF(3,2);
   TurnON(3,3);
   TurnOFF(3,3);  

   TurnON(1,4);
   TurnOFF(1,4);
   TurnON(2,4);
   TurnOFF(2,4);
   TurnON(3,4);
   TurnOFF(3,4);      
 }
 else if(number == 6)
 {
   Display(5);   
   TurnON(1,3);
   TurnOFF(1,3);   
 }
 if(number == 7)
 {
   Display(1);
   TurnON(2,0);
   TurnOFF(2,0);
   TurnON(1,0);
   TurnOFF(1,0);
 }
 else if(number == 8)
 {
   Display(6);
   TurnON(3,1);
   TurnOFF(3,1);
 }
 else if(number == 9){
   Display(7);
   TurnON(1,1);
   TurnOFF(1,1);
   TurnON(1,2);
   TurnOFF(1,2);
   TurnON(2,2);
   TurnOFF(2,2);
 }
 else if(number==10){
   Display(7);
   TurnON(1,1);
   TurnOFF(1,1);
   TurnON(1,2);
   TurnOFF(1,2);
   TurnON(1,3);
   TurnOFF(1,3);
   TurnON(1,4);
   TurnOFF(1,4);
   TurnON(2,4);
   TurnOFF(2,4);

   TurnON(0,0);
   TurnOFF(0,0);
   TurnON(0,1);
   TurnOFF(0,1);
   TurnON(0,2);
   TurnOFF(0,2);
   TurnON(0,3);
   TurnOFF(0,3);
   TurnON(0,4);
   TurnOFF(0,4);
 }else if(number == 11){
   Display(1);
   TurnON(0,0);
   TurnOFF(0,0);
   TurnON(0,1);
   TurnOFF(0,1);
   TurnON(0,2);
   TurnOFF(0,2);
   TurnON(0,3);
   TurnOFF(0,3);
   TurnON(0,4);
   TurnOFF(0,4);
 }else if(number == 12){
   Display(2);
   TurnON(0,0);
   TurnOFF(0,0);
   TurnON(0,1);
   TurnOFF(0,1);
   TurnON(0,2);
   TurnOFF(0,2);
   TurnON(0,3);
   TurnOFF(0,3);
   TurnON(0,4);
   TurnOFF(0,4);
 }
}
int main( void )
{
 // Stop watchdog timer to prevent time out reset
 WDTCTL = WDTPW + WDTHOLD;

 P2OUT = 0;            //P2 is output low
 P2DIR = BIT6 + BIT7; //P2 is output
 P2SEL = 0;            //P2 is digital i/0
 P2REN = 0;            //P2 disable pullup resistors */

 int i = 1;


 for(;{  //Digital Input
   while (P2IN & BIT7);    //wait for P1.7 to go low (buttion is pressed)
   Display(i);                 //display
   while (!(P2IN & BIT7)); //wait for P1.7 to go high (button is released)
   i = i + 1;              //increase counter
   if (i > 12) i = 0;       //maximum display is 12
 }
}

 

EDIT: I tried replacing display(i) with just TurnON(1,0), and the light turned on instantly and ever turned off, even when i applied VCC to pin 2.7...

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mnpumar

mnpumar 2

Posted
  • Author
Posted

Just tried this:

int main( void )

{

// Stop watchdog timer to prevent time out reset

WDTCTL = WDTPW + WDTHOLD;

 

P2OUT = 0; //P2 is output low

P2DIR = BIT7; //P2 is output

P2SEL = 0; //P2 is digital i/0

P2REN = 0; //P2 disable pullup resistors */

 

int i = 1;

 

 

for(;;){ //Digital Input

while (P2IN & BIT7); //wait for P1.7 to go low (buttion is pressed)

TurnON(1,0); //display

while (!(P2IN & BIT7)); //wait for P1.7 to go high (button is released)

i = i + 1; //increase counter

if (i > 12) i = 0; //maximum display is 12

delay(10000);

TurnOFF(1,0);

}

}

 

The LED stays on and never turns off from the beginning :?

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simpleavr

simpleavr 399

Posted
Posted

it looks like your P2.7 is setup as output, but u intend to use it as an input to read button.

 

P2DIR = BIT7; //P2 is output

 

u should just leave it as P2DIR = 0;

 

also, how did u wire your button, is it a tie between P2.7 and Vcc or P2.7 and Gnd?

either way, u may consider using pull-up to be more stable.

also if u can have a choice, u should avoid P2.7 as it is also XOUT (crystal)

 

from the g2x21 manual, page 6, footnote 3

 

If XOUT/P2.7 is used as an input, excess current will flow until P2SEL.7 is cleared. This is due to the oscillator output driver connection to this pad after reset
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mnpumar

mnpumar 2

Posted
  • Author
Posted

I don't really have a button, I was just connecting the pin to ground/vcc with a wire. I got it to work by doing the following:

 

int main( void )
{
 // Stop watchdog timer to prevent time out reset
 WDTCTL = WDTPW + WDTHOLD;

 P2OUT = 0;            //P2 is output low
 P2DIR = BIT7; //P2 is output
 P2SEL = 0;            //P2 is digital i/0
 P2REN = 0;            //P2 disable pullup resistors */

 P2DIR &= ~BIT7;
 int i = 1;


 for(;{  //Digital Input
   while (!(P2IN & BIT7)){
     Display(i);
   }    //wait for P1.7 to go high (button is released)
   i = i + 1;              //increase counter
   if (i > 12) i = 0;       //maximum display is 12
   while (P2IN & BIT7); //wait for P1.7 to go low (buttion is pressed)
   //delay(10000);

 }
}

 

Problem now is that it's a pretty unreliable switch. Whenever i trigger it, the number goes up a random number of times. I thought the 

while (P2IN & BIT7); //wait for P1.7 to go low (buttion is pressed)

is supposed to prevent this from happening?

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simpleavr

simpleavr 399

Posted
Posted

see the second diagram in the following link

 

http://www.rentron.com/Myke6.htm

 

also, u should set P2DIR = 0 instead of P2DIR = BIT7, your P2IN can still get reading but it may not be reliable, if your P2OUT has also set BIT7 on (which u did not), u may even blow up a pin when u use a wire to poke around.

 

from slau144e.pdf

 

8.2.3

Direction Registers PxDIR

Each bit in each PxDIR register selects the direction of the corresponding I/O

pin, regardless of the selected function for the pin. PxDIR bits for I/O pins that

are selected for other functions must be set as required by the other function.

Bit = 0: The port pin is switched to input direction

Bit = 1: The port pin is switched to output direction

 

to do non-interrupt button de-bounce, i would

 

. setup P2.7 as input, w/ pull-up enable

P2DIR = 0;

P2REN = BIT7;

P2OUT = BIT7;

. tie the button between P2.7 and Gnd (i.e. low activate)

. use a counter for de-bouncing.

 

this setup will be input normally high and button press does a low trigger. u will want to capture the transition of low to high (button release) for your activities.

while (1) {
 // u thing here, may be display
 display(i);
 unsigned wait=0;
 while (!(P2IN & BIT7) wait++;    
 // P2.7 is low, we have a key-press, wait it out
 // we will only consider it as a trigger if it takes wait to reach at least 20 counts
 // this will avoid / skip those button jitters, if no good, try a higher value
 if (wait > 20) { // or try some other value
   i++;
   if (i>=12) i=0;
 }
}

 

i haven't tried the code, just look right to me. if u tried it and still have problems, i will try something for u.

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