Setting GPIO and TRISIO

[AvionicsMaster1]

Hey, thanks for the reply and for showing the progression from functional to elegant. But would you mind verifying my logic?

Since I'm an unsophisticated person, I want to make sure I understand what's going on in the following snippet. Variables get declared, TRIS set and then LED1= !LED1 sets a 1, because its prior value was 0, turning on LED1. LED2= ! LED1 turns off LED2 because it's value is set to 1 in the previouse line. Then it loops and the !LED1 keeps toggling the state of LED1 and LED2.

Is that close? Is it necessary to set the gpio.0 or gpio.6 to 0 to make sure they turn off at start up?


.. again in a more sophisticated way:

LED1 VAR GPIO.0
LED2 VAR GPIO.6

TRISIO = %00011110

main:
LED1 = !LED1
LED2 = !LED1
PAUSE 500
GOTO MAIN

END

Cheers

Al.[/QUOTE]

[aratti]

Is that close?

You have got it!

Is it necessary to set the gpio.0 or gpio.6 to 0 to make sure they turn off at start up?

No, since Led1 and Led2 has been declared as alias of gpio.0 and gpio.6. So if you want set them to zero just state Led1=0 : Led2=0.

Cheers

Al.

[Heckler]

Also... don't overlook the fact that GPIO.3 can only be an INPUT. It defaults to MCLR or "Master Clear with internal pull-up". This means it will reset the chip whenever it goes low.

In order to make it a normal input pin you MUST change the "Configuration Word Register" bit 5. This register can ONLY be defined once at the time of programming. I think some refer to it as the "FUSE bits" or "configuration fuses" This special register can only be changed each time you program the chip and is not change-able during runtime of your program.

I think I lost a few hairs and much sleep trying to understand the details of configuring PIC's and the registers. I now keep the .pdf of what ever chip I am working with open and refer to it often as I am defining the functionality of my chip and the various I/O pins, analog, comparators, pulse width modulation, etc, etc.

I hope this helps and is not too basic for your level.

In the beginning I tried to use GPIO.3 as a normal input and could not for the life of me figure out why it kept resetting my program...

regards