PIC16F1826 output voltage unstable

[Cebro]

Hey guys,

I am developing a project with the PIC16F1826 and one of my outputs is flotoating like 1.9V, 2.9V and I can´t find why. I already check the ANSEL registers and initialize the PORTs at 0. It start´s when I add more if statements in my checkmodule() function...

Here is the code:

int c=0;

int c1_m1 = 0;

int c1_m2 = 0;

int c1_m3 = 0;

void main(){

OSCCON = 0b01110000;

ANSELA = 0b00000000;

ANSELB = 0b00000000;

TRISA=0b11111111;

PORTA = 0b00000000;

TRISB=0b00000000;

PORTB = 0b00000000;

while(1){

checkmodules();

module_status();

}

}

void checkmodules(){

if(PORTAbits.RA1==1){

if(c1_m1==0){

c++;

c1_m1=1;

}

}

if(PORTAbits.RA1 == 0){

if(c1_m1 == 1){

c--;

c1_m1 = 0;

}

} 

// When I add mores of this if´s, I start to have the problem with my PORTB outputs...

} // end checkmodules()

 

void module_status(){

if(c>0 && c<=3){

PORTBbits.RB4 = 1;

}

if(c==0){

PORTBbits.RB4 = 0;

}

if(c>=3){

PORTBbits.RB5 = 1;

}

if(c<3){

PORTBbits.RB5 = 0;

}

}// end module_status()

[holdmybeer]

Hi!

I'm not sure that's happening, maybe we can find this together. First, check out this thread about PORT and LAT:

If you like to set an output, use LAT registers instead of PORT.

Second thing is your code: Is it your intention that variable c is going negative?

if (PORTAbits.RA1 == 0) {
    if (c1_m1 == 1) {
        c--;
        c1_m1 = 0;
    }
}

You used an "int" type, which means c is a signed 16 bit integer. You could use more explicit types like "int16_t" and check if your code regards the negative case properly.

Third thing I noticed: Your while() loop is running with maximum speed. It may be better to have a timing in your main sequence to get a more predictable runtime. For example, just add Timer0 to your main loop:

// configure TMR0 according to datasheet, section 20.2
OPTION_REG = 0b11010011;
while(1) {
    // wait here for next cycle
    while(INTCONbits.TMR0IF == 0);
    INTCONbits.TMR0IF = 0;
    
    // execute cyclic code
    // ...
}

About your floating output: How did you measure this? If you have used a multimeter, you likely are measuring the RMS value of a rapidly changing digital output. The TMR0 helps you getting a deterministic behavior, a scope helps you seeing what is really going on...

And did you halt the code at certain points and observed the behavior of your pins? With a PICKit or any other debugger attached to your controller, just run a debug session and set a breakpoint where you expect bad things to happen 🙂

 

 

 

 

 

[Orunmila]

I would also suggest you take a look at this because you seem to be writing to the port register bits which will cause read/modify/write errors. Is it possible that the pin is actually toggling really fast? 

 

 

[ric]

Was any solution found?

I note the CONFIG bits have not been shown.

The chip will not run if the oscillator has not been set up correctly, and it will be rapidly resetting if the WDT has not been disabled.