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stu
Joined: 11 Oct 2006
Posts: 3
Location: south australia
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| coding problem |
 Posted: Wed Oct 11, 2006 9:26 pm |
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Hi,
im trying to build a 16F876A based maximum power point tracker (dc-dc converter). the role of the PIC is to adjust the PWM duty cycle to track the optimal output power/current. my code compiles ok but the PIC just sits there doing nothing.
Ive consulted friends and the compilers help directory but still havent found the problem.
The PIC was tested with a quick asm code and performed as expected.
im using pcw compiler version 3.6.0.93.
Can anybody see anything obvious that im doing wrong or havent done??
Thanks in advance,
Stuart.
| Code: |
#include <16f876a.h>
#DEVICE *=16 ICD=TRUE
#use Delay(Clock=20000000)
// set up serial interface
#use RS232(Baud=9600,Xmit=PIN_C6,Rcv=PIN_C7,brgh1ok)
//-------------------------------------------------------------------------------
// To obtain an unbiased sample of the input, take a few and average
// the set. Using the central limits theorem, we should use at least 30.
//--------------------------------------------------------------------------------
float av_sample(byte pin_to_read)
{
int i,lim = 30;
float av = 0;
set_adc_channel(pin_to_read);
delay_us(100);
for (i=1; i<=lim; ++i) {
av += read_adc();
delay_us(100);
}
return(av/lim);
}
//--------------------------------------------------------------------------------
// The following has a bit of a setup procedure, then enters an infinite
// loop, continually searching for the optimal power point.
//--------------------------------------------------------------------------------
main()
{
CONST byte Ibatt_pin = 0;
//only consider output current as this is roughly proportional to P_out
float Psend, Ibatt = 0.0, old_Ibatt = 0.0;
long delta = 1, pwm_coeff, duty;
byte led = 0;
output_low(PIN_C3); // turn off FETs by clearing EN pin on FET driver
setup_port_a(ALL_ANALOG); // set up A/D ports
setup_adc(adc_clock_div_32); // start A/D clocks
setup_timer_2(T2_DIV_BY_1, 49, 1); // set pwm frequency to 100kHz
setup_ccp1(CCP_PWM); // Set CCP1 as a PWM
pwm_coeff = 2; // so PWM = 100% @duty = 100
duty = 85; // set init duty cycle to 85%
set_pwm1_duty(pwm_coeff*duty); // set initial PWM duty cycle
output_high(PIN_C3); // set enable pin on FET driver
output_high(PIN_C0); // turn on heartbeat led
delay_ms(1000);
while(TRUE) // loop forever
{
if (old_Ibatt > Ibatt) // past the peak?
{
delta = -delta; // then reverse the direction of search
}
old_Ibatt = Ibatt; // remember the old value for comparison
duty += delta; // keep climbing
if (duty > 100) // check limits of duty cyle
{
duty = 100;
}
else if (duty < 0)
{
duty = 0;
}
set_pwm1_duty(pwm_coeff*duty); // restet actual duty cycle
Ibatt = av_sample(Ibatt_pin)/41; // approximate fudge factor to convert to Amps
Psend = Ibatt*14; // As P=VI and output voltage = 14V
printf("%c\r\n", Psend); //send power info via RS232
output_bit(PIN_C0,(++led & 0x01)); //Flash LED so know prog hasn't frozen
delay_ms(500);
}
}
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Last edited by stu on Thu Oct 12, 2006 12:01 am; edited 2 times in total |
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stu
Joined: 11 Oct 2006
Posts: 3
Location: south australia
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| Posted: Wed Oct 11, 2006 9:36 pm |
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Thanks for the editing tip PCM programmer.
Last edited by stu on Thu Oct 12, 2006 12:03 am; edited 1 time in total |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Oct 11, 2006 10:45 pm |
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| Quote: | | for (i=1; i<lim> Ibatt) |
Notice how this section of your code (in the first part) didn't post
correctly. You need to edit your post, and delete the whole first
section, and make a fresh copy and paste from your original program.
Except this time, disable HTML when you post it. Look for the checkbox
just below the posting window. Select that box. Example:
| Quote: | | x Disable HTML in this post |
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kypec
Joined: 20 Sep 2003
Posts: 54
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| Posted: Thu Oct 12, 2006 12:41 am |
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There is missing oscillator setting in your example, you should specify what is the clock source for your PIC in this application (XT or HS or IntRC?)
Moreover, you have included ICD=TRUE statement. Unless you use the ICD unit to program and run your target application, you should omit that statement, otherwise your PIC expects it is controlled from the external ICD debugger hardware and will not run alone. |
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