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Message |
kazama
Joined: 01 Sep 2009
Posts: 10
Location: Malaysia
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| code help needed |
 Posted: Tue Sep 01, 2009 9:19 am |
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Hi guys, I need some help on my coding. The robot that I'm doing is slam robot. But now I need to fix the sensor problem. I think the coding is alright but, after I burned the program to the PIC, only the left wheel is moving. Can someone check the program? Got blur at d moment..
| Code: |
#include <16f877a.h> //declare a PIC header
#device adc=8 //set the bit for ADC
#fuses hs,nowdt,noprotect //set the PIC protection
#use delay (clock=20000000) //set the clock frequency to 20 kHz
int val1; //val1 = middle sensor(ADC Value)
int val2; //val2 = left sensor(ADC Value)
int val3; //val3 = right sensor(ADC Value)
int vref; //voltage reference
void left_motor(int speed); //left motor function
void right_motor(int speed); //right motor function
#byte porta=5
#byte portc=7
//motor_ra RC0 motor_rb RC3
//motor_la RC4 motor_lb RC5
void main() //main function
{
vref=0x4d; //voltage reference = 2.5v
set_tris_c(0); //port b as output
setup_port_a(all_analog); //enable port a as ADC port
setup_adc(adc_clock_internal); //set ADC clock
setup_ccp1(ccp_pwm); //enable ccp1
setup_ccp2(ccp_pwm); //enable ccp2
setup_timer_2(t2_div_by_4,100,1); //set post scaler timer
While(true)
{
portc=0b00010001;
set_adc_channel(0);
val1=read_adc();
set_adc_channel(1);
val2=read_adc();
set_adc_channel(2);
val3=read_adc();
if(val1>vref)
{
if((val2>vref)&&(val3>vref))
{
left_motor(70);
right_motor(70);
}
else if ((val3<vref)&&(val2>vref))
{
left_motor(0);
right_motor(70);
}
else if ((val2<vref)&&(val3>vref))
{
left_motor(70);
right_motor(0);
}
}
else if (val1<vref)
{
if((val2>vref)&&(val3>vref))
{
left_motor(30);
right_motor(30);
}
else if ((val3<vref)&&(val2>vref))
{
left_motor(0);
right_motor(70);
}
else if ((val2<vref)&&(val3>vref))
{
left_motor(70);
right_motor(0);
}
}
else
{
left_motor(0);
right_motor(0);
}
}
}
void left_motor(int gear)
{
set_pwm1_duty(gear);
}
void right_motor(int gear)
{
set_pwm2_duty(gear);
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Sep 01, 2009 12:19 pm |
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| Quote: | #include <16f877a.h> //declare a PIC header
#device adc=8 //set the bit for ADC
#fuses hs,nowdt,noprotect,nolvp |
Add NOLVP to the #fuses as shown above in bold. CCS does this
by default in vs. 4.xxx, but I don't know what version you're using.
| Quote: |
While(true)
{
portc=0b00010001;
set_adc_channel(0);
delay_us(20);
val1=read_adc();
set_adc_channel(1);
delay_us(20);
val2=read_adc();
set_adc_channel(2);
delay_us(20);
val3=read_adc();
if(val1>vref)
{ |
Add a short delay (20 us) after you change the ADC channel, as shown
above in bold. This is stated in the PIC data sheet:
| Quote: |
11.1 A/D Acquisition Requirements
After the analog input channel is selected (changed),
this acquisition [delay] must be done before the conversion
can be started.
TACQ = 19.72s
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rnielsen
Joined: 23 Sep 2003
Posts: 852
Location: Utah
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| Posted: Tue Sep 01, 2009 12:25 pm |
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Just a quick observation here.... You need to insert a small delay after each channel select command to give the ADC holding capacitor time to charge to the new voltage level. Look at the spec. sheet to calculate the proper time delay. If you want a rough estimate, I believe 10uS was enough time.
Ronald
Edit: Too slow again... |
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kazama
Joined: 01 Sep 2009
Posts: 10
Location: Malaysia
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| Posted: Wed Sep 02, 2009 12:03 am |
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| still can't work. only left wheel run. do i need to add all portc=something to all looping? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Sep 02, 2009 1:09 am |
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I didn't look closely at your if-else code. I suggest that you make a
simple test program that only runs the right wheel. Don't use any if-else
statements. Just run the right wheel. See if that works. |
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kazama
Joined: 01 Sep 2009
Posts: 10
Location: Malaysia
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| Posted: Wed Sep 02, 2009 2:26 am |
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| I got left and right sensor works. Can move now. But having a problem on front sensor which is RA0. To move the robot forward I use portc=0b00010001 and portc=0b00101000 to reverse it. But still cannot reverse. How should I fix it? Do you think I need to change the vref value? Current value that I use is vref=0x4 which is 0.1v. |
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