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Begineer need help about GPIO, PLEASE

Sat, 19 Jul 2008 07:15:32 -0700

I'm new in arm, i don't quite understand about in the IOPIN...
for example,
#define LED 1<<24
#define KEY1 1<<16

int main(void)
{
unsigned int key = 0;

PINSEL0 = 0;
PINSEL1 = 0;

IO0DIR = LED;
IO0SET = 0x1010000; //set both P0.24 & P0.16 to high

while(1)
{
key = IO0PIN;
if(key==?) //key is pressed, will be "0"
...
...
}
}

i got a button and a led connected to P0.16 and P0.24, and i would like to read the status of the button in order to turn a led. but what value actually i need to put in the question mark??
don't know if i miss understand the concept.....
thank you

Re: Begineer need help about GPIO, PLEASE

contact@nospam.com (Ajay Bhargav) — Sat, 19 Jul 2008 08:28:29 -0700

its like this.
.

CODE:

if(key&(key1)){
   //not pressed
}
else{
   //Pressed
}
 

Re: Begineer need help about GPIO, PLEASE

contact@nospam.com (Ajay Bhargav) — Sat, 19 Jul 2008 21:36:47 -0700

thank you, but i still confuse about it. if it is IO0SET = 0x1010000, so IO0PIN will read back 0x1010000?? also i don't quite understand the use of "key&(key1)"

if IO0PIN really read back 0x1010000, and "&" with key1 it becomes key1 that means the button is not pressed. if the button is pressed, it becomes 0.

don't know if i make it wrong, thank you

Re: Begineer need help about GPIO, PLEASE

contact@nospam.com (Ajay Bhargav) — Sun, 20 Jul 2008 22:41:28 -0700

you can try like this.. and hope it explians itself..

CODE:

#define LED 1<<24
#define KEY1 1<<16

int main(void)
{
unsigned int key = 0;

PINSEL0 = 0;
PINSEL1 = 0;

IO0DIR = LED; // shyam: LED pin set as output.. other pins default to input
 
IO0SET = 0x1010000; //set both P0.24 & P0.16 to high

while(1)
{
key = IO0PIN;
if((key&key1)==key1) //key is pressed, will be "0"
...
...
}
}
 

now while only the led pin is set as output pin..it will efffect ony the led not the key1

so if u want the key1 to be effective high u will have to do

IODIR1 = Key1| Led1;
IOSET1 = Key1;

//and then again make key as input
IODIR1 = Led1;

hope that clears abit of your doubts...