Code ignores IF Statement

Here is my code:

Code:

---

char adc(unsigned char);
unsigned char temp, temp1, temp2,temp3,temp4,temp5,send;


unsigned int temp_res;
void Forward (void){
        RC3_bit=1;//right forward
        RC4_bit=0;//right reverse

        RC6_bit=1;//Left forward
        RC7_bit=0;//Left Reverse


        RC0_bit=1;//right enable
        RC1_bit=1; //Left enable

}
void Reverse (void){
        RC3_bit=0;//right forward
        RC4_bit=1;//right reverse

        RC6_bit=0;//Left forward
        RC7_bit=1;//Left Reverse


        RC0_bit=1;//right enable
        RC1_bit=1; //Left enable
}

void Right (void){
        RC3_bit=1;//right forward
        RC4_bit=0;//right reverse

        RC6_bit=0;//Left forward
        RC7_bit=0;//Left Reverse


        RC0_bit=1;//right enable
        RC1_bit=1; //Left enable
}

void Left (void){
        RC3_bit=0;//right forward
        RC4_bit=0;//right reverse

        RC6_bit=1;//Left forward
        RC7_bit=0;//Left Reverse


        RC0_bit=1;//right enable
        RC1_bit=1; //Left enable
}



void STOP (void){
        RC3_bit=0;//right forward
        RC4_bit=0;//right reverse

        RC6_bit=0;//Left forward
        RC7_bit=0;//Left Reverse


        RC0_bit=1;//right enable
        RC1_bit=1; //Left enable
}

void main(void) {

        ANSELH = 0x00;
        ANSEL = 0x00; // Set AN2 pin for A/D
        TRISC = 0x00; // Set data Direction on Port C (output)
        PORTC = 0x00; // Start with zero on Port C
        TRISB = 0xF0; // Set Port B as an input port
        PORTB = 0x00;

       
        C1ON_bit = 0;              // Disable comparators
        C2ON_bit = 0;
        PWM1_Init(8000);
        PWM1_Start();


    while(1){

          temp_res = ADC_Read(2);  // Get 10-bit results of AD conversion
          temp1 = temp_res >>2;

          PWM1_Set_Duty(temp1);

          delay_ms(100);
       
        if (RB4_bit == 1)
            {

            Forward();

            }
         
          }
}

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The code is for a PIC16F690 which is connected to an H-Bridge. The intent of the code is to drive the robot forward whenever RB4 is high.

Whenever I run the code it ignores the IF statement and the Forward() function is called and the robot immediately goes forward.

Any ideas?

What is connected to the port pin that is being read by RB4? Once the robot starts forward, how do you stop it?

Jim

Whether I connect RB4 to ground or power it still continues to go forward.

I initialized PORTB as all inputs.

I guess to better answer the question. I have a push button connected between RB4 and power.

FYI: The name of the signals on pin RB4 are "RB4/AN10/SDI/SDA".
The name AN10 suggests analog input; on PIC chips they normally default to analog.
You likely need to disable analog input.

You might also check to make sure SDI and SDA are not enabled.

From Chip Manual

Quote:

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The ANSEL and ANSELH registers are used to disable
the input buffers of I/O pins, which allow analog voltages
to be applied to those pins without causing excessive
current. Setting the ANSx bit of a corresponding pin will
cause all digital reads of that pin to return ‘0’ and also
permit analog functions of that pin to operate correctly.

---

Tim S.

Does this port perhaps have internal pullups? Looking at the data sheet for this processor it appears that it does. So show how you have connected your switch to this pin. You will probably need to connect this switch to ground and reverse your logic.

Jim

I set ANSEL = ANSELH = 0x00;

This should disable the analog input right?

Jim,

Whether I connect it to power or ground it continues to go forward.

Did you initialize your TRISB register?

Quote:

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Originally Posted by Neil Naik

I set ANSEL = ANSELH = 0x00;

This should disable the analog input right?

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I think that should do it.

Tim S.

When you talk about connecting it to ground, are you still using a switch? Show you connection schematic. You will probably need to connect the switch to ground and change your logic. This pin is driven high by internal inputs. You should also think about adding logic to stop the robot when your switch is not pressed.

Jim

Yes matticus I defined it as TRISB = 0xF0;

I planned on using RB4, RB5, RB6, and RB7 later on after I get the Forward function working.

Have you tried:

Code:

---

if(RB4_bit == 1)
    Forward();
else
    STOP();

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Because when RB4 is high, it sets certain outputs.
I don't see these outputs changing anywhere else in your "while" loop, so when RB4 goes low, the outputs are still going to remain as they were (because they haven't been told to change).