Begineer need help about GPIO, PLEASE : 8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes

Forums

8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes :: Forums :: Discuss and Learn :: ARM Development		<< Previous thread \| Next thread >>
Begineer need help about GPIO, PLEASE


Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

Author

Post

mikemike

Sat Jul 19 2008, 07:15AM

Registered Member #6498

Joined: Fri Mar 07 2008, 12:09AM

Posts: 6
Thanked 0 times in 0 posts

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

[ Edited Sat Jul 19 2008, 09:30PM ]

Ajay

Sat Jul 19 2008, 08:28AM

Rickey's World Admin

Registered Member #1

Joined: Fri Feb 24 2006, 04:56AM

Posts: 3681
Thanked 684 times in 646 posts

its like this.
.

CODE:

if(key&(key1)){

   //not pressed

}

else{

   //Pressed

}

www.rickeyworld.info
If you feel satisfied with the user's forum reply please click on the thank button.

Obey forum rules!
Respect others!

This post has been thanked 1 time

mikemike

mikemike

Sat Jul 19 2008, 09:36PM

Registered Member #6498

Joined: Fri Mar 07 2008, 12:09AM

Posts: 6
Thanked 0 times in 0 posts

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

shyam

Sun Jul 20 2008, 10:41PM

Registered Member #2984

Joined: Mon Aug 06 2007, 11:33AM

Posts: 719
Thanked 107 times in 103 posts

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...