I feel silly, but....

Vizier87 · Jun 14, 2011

Hi guys,
Sorry to ask such a simple question.
I'm using MikroC now (since I've been using Assembly for simple tasks) and couldn't get my PIC18F4455 to turn on an LED. I read the initialization on the PORTB part on the datasheet, which states:

CLRF PORTB ; Initialize PORTB by
; clearing output
; data latches
CLRF LATB ; Alternate method
; to clear output
; data latches
MOVLW 0Eh ; Set RB<4:0> as
MOVWF ADCON1 ; digital I/O pins
; (required if config bit
; PBADEN is set)
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISB ; Set RB<3:0> as inputs
; RB<5:4> as outputs
; RB<7:6> as inputs

Now here's my C code, trying to turn on all the PORTB pins,

C:

void main() {

     PORTB=0X00;
     LATB=0X00;
     ADCON1=0X0F;
PORTB= 0b11111111;
while (1){
}
}

Sometimes the PIC turned on well, but then it turns off again when I interrupt its supply i.e it doesn't seem to return to its original state. I suspect it might have to do with other configurations, but I suppose MikroC covers such details when I used the Project Wizard.

Any help would be highly appreciated.

Vizier87

Nigel Goodwin · Jun 15, 2011

I can't help you with C, but you don't appear to be setting TRIS to make the pins outputs?.

Vizier87 · Jun 15, 2011

yeah, I missed out the TRISB while pasting the code, but still, the results are the same. I'm not sure if I missed out anything else. It's just turning a pin on....

Ian Rogers · Jun 15, 2011

ANSELH has to be cleared to use most of portb they are all on by default..

Vizier87 · Jun 15, 2011

Ian Rogers said:
ANSELH has to be cleared to use most of portb they are all on by default..

What do you mean ANSELH? I didn't come across that along the 4455 datasheet.

Vizier87 · Jun 15, 2011

okay, so I tried it like this:

C:

void main() {
     ANSELH=0X00
     PORTB=0X00;
     LATB=0X00;
     ADCON1=0X0F;
     TRISB=0X00;
PORTB= 0b11111111;
while (1){
}
}

But still no avail.

Pommie · Jun 15, 2011

It sounds like you are getting a brown out. Try turning on the brownout reset in the config.

Mike.

Ian Rogers · Jun 15, 2011

My bad (thats the newer processors) set ADCON1 to anything above 0x8 (0xA if you want porta analogue) Sorry about that to many variations now..

Ian Rogers · Jun 15, 2011

Like Pommie said.. What voltage are you running at...

Vizier87 · Jun 15, 2011

Pommie said:
It sounds like you are getting a brown out. Try turning on the brownout reset in the config.

Mike.

Hi Mike, I'm using MikroC and that's where I'm a bit at loss. During the days I'm using templates of ASM, the config part is shown properly.

However, how do I go about configuring the Config part through MikroC? Is it done as part of the code itself?

Thanks.
Vizier87

Vizier87 · Jun 15, 2011

Ian Rogers said:
My bad (thats the newer processors) set ADCON1 to anything above 0x8 (0xA if you want porta analogue) Sorry about that to many variations now..

Hi Ian, I've set the ADCON1 to 0x0F. That's with accordance to the setting that I want so all PORTB pins are output.

Pommie · Jun 15, 2011

Vizier87 said:
Hi Mike, I'm using MikroC and that's where I'm a bit at loss. During the days I'm using templates of ASM, the config part is shown properly.

However, how do I go about configuring the Config part through MikroC? Is it done as part of the code itself?

Thanks.
Vizier87

I'm afraid I don't use MikroC so not sure how you set the config. Guess you'll have to check the manual.

Mike.

Mr RB · Jun 15, 2011

You set the config under the top menu; Project -> Edit_Project
then check the config boxes as desired.

You should have a good read through the PIC datasheet under "Special features of the CPU" chapter which described the effect of all the config options.

Vizier87 · Jun 15, 2011

Mr RB said:
You set the config under the top menu; Project -> Edit_Project
then check the config boxes as desired.

You should have a good read through the PIC datasheet under "Special features of the CPU" chapter which described the effect of all the config options.

hi Mr RB,
yeah thanks for your info. I'll try to get a look into it.

Vizier87 · Jun 16, 2011

Hi guys,
Still no avail. I changed the Brown Out to "Disabled in Hardware, SBOREN Disabled". Anything else which needs to be changed?BTW, my crystal osc is 20 MHz, just to inform you guys.
Here's a screenshot:
**broken link removed**

Vizier87

Pommie · Jun 16, 2011

Set the "Brown Out Detect" to on.

Mike.

Pommie · Jun 16, 2011

Also, if you have a 20MHz crystal then the top box (prescaler) needs to be 5.

Mike.

Vizier87 · Jun 16, 2011

Pommie said:
Set the "Brown Out Detect" to on.

Mike.

Hi, thanks for the input. The Brownout options are:
**broken link removed**
Which one should it be?

Also here's my code, please check it out:

C:

void main() {

PORTB=0x00;
LATB=0X00;
ADCON1=0X0F;
TRISB=0X00;
}
PORTB= 0b11111111;
while (1){
}

Also, how about the CPU system clock Post Scaler?
thanks.

Vizier87 · Jun 16, 2011

okay, something's definitely happening, but it's pretty strange. my PORTC pins turned on!
the pins: C0,C1,C2,C6 and C7

Pommie · Jun 16, 2011

With a 20MHz crystal you need the prescaler set to 5 so the PLL gets 4MHz. The output will be 96MHz and so you need to divide it by something like 4 to get a usable 24MHz. So postscaler = 4. The oscillator type should be HSPLL (High speed - pll enabled).

The brownout reset should be enabled in hardware.

Mike.

I feel silly, but....

Active Member

Super Moderator

Active Member

User Extraordinaire

Active Member

Active Member

Well-Known Member

User Extraordinaire

User Extraordinaire

Active Member

Active Member

Well-Known Member

Well-Known Member

Active Member

Active Member

Well-Known Member

Well-Known Member

Active Member

Active Member

Well-Known Member

Similar threads

Privacy & Transparency

Privacy & Transparency