Post by thread:Read a value on PORTB

I need a Help. Hi, i am a begginer on mcus, and I started on 16f84 has 3 weeks, i am training the possibilities of this microcontroler and i need help with a problem. I am trying to do something very simple : press a button on RB3 and turn on a led on RB4. But i don't know how to do that !! I've bought a book about pic (the only in portuguese yet, but this book have wrong examples and informatons - it's a crap book !!!) I need to know how i read the value of RB3 ( i am using the pull up resistor - so i get the low level when i press the button) and how i work with this. Thanks a lot !!!! Leonardo Schunk _____________________________________________________________ Do You Yahoo!? Free instant messaging and more at http://messenger.yahoo.com

This ought to bring out a bunch of answers. Here's one: portb equ 0x06 ; org 000 ; movlw b'111101111' tris portb ;portb set to inputs except for port 4 bcf portb,4 ;clear port b s1 btfss portb,3 ;bit 3 high? goto s1 ;no, wait for it to go high s2 btfsc portb,3 ;bit 3 low - wait until button released goto s2 ;not released bsf portb,4 ; set port b loop goto loop end {Original Message removed}

Perhaps this simple "echo" routine may be more useful to start with, apologies to Dan Creagan: portb equ 0x06 ; org 0 ; movlw b'111101111' tris portb ;portb set to inputs except for port 4 loop btfss portb,3 ; bit 3 high? bcf portb,4 ; if not, clear port b,4 btfsc portb,3 ; bit 3 low? bsf portb,4 ; if not, set port b,4 goto loop end -- Cheers, Paul B.

Hi Leonardo. Couple of academical examples more... WBR Dmitry. > portb equ 0x06 > ; > org 0 > ; > movlw b'111101111' > tris portb ;portb set to inputs except for port 4 Loop: rlf PORTB,W ;read from PORTB and shift it to W movwf PORTB ;pit it back to PORTB goto Loop ;... Loop: movlw 0 ;if PORTB.3=0 load W.4=0 btfsc PORTB,3 movlw 0x10 ;if PORTB.3=1 load W.4=1 movwf PORTB goto Loop ;... > loop btfss portb,3 ; bit 3 high? > bcf portb,4 ; if not, clear port b,4 > btfsc portb,3 ; bit 3 low? > bsf portb,4 ; if not, set port b,4 > goto loop

Ok great, but why not do it in one line of code wth a higher level language. Take Pic BASIC for example. Here's how to read a port: ByteVariable = PortB That's it. Regards, Darren