12F675 / MCLR use

Printable View

- 3rd September 2009, 19:56
Acetronics2

12F675 / MCLR use

Hi,

Who could explain me that ???

This simple program is a flip-flop with button debouncing ... simple, eh !

( Button1 is on the low side - LOW level if pushed )

When using MCLR ... output ( GPIO.2) is LOW at power-up ... Ok

When disabling MCLR ( internal reset ) ... output is HIGH at power-up ... ???
Instead to what it should be !!!

Did I miss something ???

Code:

' Madproject ' 'Anti rebond pour sauter à la perche ( ??? ) ' ' 16F629 mode INTOSC @ 4 Mhz ' ' le 03/09/2009 139 Lignes '****************************************************************************** '****************************************************************************** '****************************************************************************** ' CONFIG '****************************************************************************** @ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_ON & _CP_OFF & _BODEN_ON DEFINE OSC 4 DEFINE OSCCAL_1K 1 DEFINE BUTTON_PAUSE 100 ADCON0 = 0 ANSEL = 0 CMCON = 7 VRCON = 0 OPTION_REG.5 = 0 OPTION_REG.7 = 1 'Disable Pull-Ups Bouton1 VAR GPIO.0 Bouton2 VAR GPIO.1 Sortie VAR GPIO.2 'LedVisu VAR GPIO.3 ' Attention : Sortie PIC en C/O !!! LedVisu VAR GPIO.4 'set VAR GPIO.5 x VAR byte Delay VAR byte GPIO = %00000011 'All pins LOW IF outputted - no startup bug. TRISIO = %00000011 'set GPIO.0 & GPIO.1 as inputs Others Output '****************************************************************************** Attente: ' On attend !!! '****************************************************************************** Delay = 0 BUTTON Bouton1,0,255,0,Delay,1,Action ' Poussoir à la masse enfoncé PAUSE 10 ' 10 ms entre scans GOTO Attente ' Non? : retour départ '****************************************************************************** Action: ' On a enfoncé le bouton plus de 100 ms '****************************************************************************** TOGGLE Sortie ' On inverse la sortie TOGGLE LedVisu '****************************************************************************** Attente2: ' On attend que le bouton soit relâché ... '****************************************************************************** Delay = 0 BUTTON Bouton1,1,255,0,Delay,1,Attente ' Le bouton est il relaché ??? ' GOTO Attente2 ' NON On boucle '****************************************************************************** END

Alain
- 3rd September 2009, 21:17
Melanie

Never trust the state of any I/O on Power-Up - regardless of what the Datasheet says.

Always preset your I/O's within your program to what you want them to be as one of the first things you do when initialising the PIC.
- 3rd September 2009, 22:17
dhouston

From the datasheet...

Quote:

Figure 3-3 shows the diagram for this pin. The GP3 pin
is configurable to function as one of the following:
• a general purpose input
• as Master Clear Reset

and...

Quote:

bit 5 MCLRE: GP3/MCLR pin function select(5)
1 = GP3/MCLR pin function is MCLR
0 = GP3/MCLR pin function is digital I/O, MCLR internally tied to VDD

and from your config fuses...

Quote:

_MCLRE_ON
- 4th September 2009, 00:40
Melanie

I think Alain is talking about GPIO.2 having an anomally when you configure GPIO.3 (MCLR) for different states. In theory it shouldn't effect that pin...
- 4th September 2009, 02:36
dhouston

Quote:

Originally Posted by Melanie

I think Alain is talking about GPIO.2 having an anomally when you configure GPIO.3 (MCLR) for different states. In theory it shouldn't effect that pin...

Ahhh! I misunderstood and thought he was trying to make GPIO.3 an output although I expected he would know better. I should have known better.

What happens if the order of the TRISIO = and GPIO = statements are reversed?
- 4th September 2009, 08:22
Acetronics2

Quote:

Originally Posted by Melanie

Never trust the state of any I/O on Power-Up - regardless of what the Datasheet says.

Always preset your I/O's within your program to what you want them to be as one of the first things you do when initialising the PIC.

Hi, Mel

You do know the only one I trust in, is you, Mel ... ( Violins [ON] , Crooner [ON], Rose Petals drop [ON], Champagne [ON] ... )

I just think you missed my two I/O Config lines ... ( Was late, eh ...)

I must tell it ALSO affects GPIO.4 ... so, I have to try adding a little PAUSE after those CONFIG Lines, I smell a Power on little issue ... That make BUTTON read a low level when power up ...

OR May be a " HIGH GPIO.0 " Command before the first BUTTON Command to ensure the High Level ...

Testing a HIGH level for Button1 pressed is to also an idea ( some capacitive effects on GPIO.0 ??? ... despite it has no load but a Pullup resistor !) ...

But, that's not something " normal " ...

Alain
- 4th September 2009, 10:18
Acetronics2

Silicon bug ??? The end

As I smelled ...

Adding a little PAUSE 50 ( 40 is not enough ! ) just past the I/O config Lines solved the issue ...

HIGH GPIO.0 didn't work ...

Alain ( bug killer ...)