problem with getkey function on 8051 in c

vacant34 · Nov 25, 2012

hi everybody
im am building a lcd with a keypad it also has a software clock
i have a issue with using the getkey() function in c. I want to ignore the function unless the dav changes
but what iv tried has not worked so far and the program gets stuck on getkey() and messes up the clock.
I know I could use a timer to build the clock but for know id just like to ignore the getkey() until is need it
so could i get some idea how to do this or a simple code for a clock based in the timers.
thank you

while(DAV==1);
{
getkey(key);
}

*****************************************************************/
unsigned char getkey(unsigned char key)
{
//unsigned char key;
while(!DAV);
key=P1&0x0f;
while(DAV);
return key;
}

johnny_b4e · Nov 25, 2012

I'm not quite sure if I understand what you mean, but if you need to periodically check for button event try this:

Code:

unsigned char key_event(void)
{
[INDENT]static unsigned char LastState;
unsigned char pin_state;
unsigned char event = 0;

pin_state = P1 & 0x01;    // Or whatever is your port read methode

if(pin_state != LastState && pin_state)
{
[INDENT]event = 1;[/INDENT]
}

LastState = pin_state;

return event;[/INDENT]
}

If you place this function inside your loop you can check for button event not interrupting other stuff.

Jigar 4 Electronics · Nov 25, 2012

vacant34 said:
while(DAV==1);
{
getkey(key);
}

*****************************************************************/
unsigned char getkey(unsigned char key)
{
//unsigned char key;
while(!DAV);
key=P1&0x0f;
while(DAV);
return key;

}

I think the problem is in code :

you're returning "key", but where ??

it should be like :

dummy = getkey(key);

or

getkey(&key);

out of above to option you need to change the getkey function corresponding to the option you've chose.

for more detail please see this : (see the call be reference section - you should use that section in your case)
https://www.codingunit.com/c-tutorial-call-by-value-or-call-by-reference

vacant34 · Nov 25, 2012

hi i know that code looks pretty bad but iv been messing with it so long iv just ended up trying stuff.
that part of the code works but will wait for a kepress and i want to ignore it unless we get that keypress its slowing down my clock. it will return a value to the main.
but i think i will find it worth going over again to see where i have any logicial mistakes thank you

- - - Updated - - -

thank you that looks pretty good i try that as soon as i get home.hopefully the getkey will be ignored unless it gets the keypress

problem with getkey function on 8051 in c

vacant34

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johnny_b4e

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Jigar 4 Electronics

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vacant34

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problem with getkey function on 8051 in c

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