set_pwm_duty()

[Jim]

Could some one explain the math behind the set_power_pwm0_duty() command and where I've gone wrong?
My goal is to set the pwm duty between 40-100% for a simple motor controller. But when I hook the output pins to a scope, I can't seem to get consistent results. I've tried hard coding the value from set_power_pwm0_duty() and depending on when I've done it, I'v gotten values from 2750 up to 6000 to get 100% duty.
I'm sure I'm overlooking something but I have NO clue what.




#include<18f4331.h>

#device adc=10
#fuses INTRC,NOWDT,NOPROTECT,NOLVP, NOBROWNOUT
#use delay(clock=8000000) //8Mhz
#use rs232(baud=9600,xmit=PIN_E0,rcv=PIN_E1,parity=n,bits=8,INVERT)
setup_oscillator(OSC_8MHZ);

#define FORWARD 1
#define BACKWARD 0
#define OFF 0

int16 liLeftDuty;
int16 liRightDuty;


//////////////// functions ////////////////////////
void move(int left_speed,int left_direction, int right_speed, int right_direction);


void main(void)
{
/***********************************
freq= Fosc / (4*(period + 1) * postscale)
or
period = (Fosc /( 4 * freq * postscale)) -1

if we want 10khz
period =( 8mhz /(4 * 10khz * 1) -1
peroid = 199;
*****************************************/

int period = 199;

setup_power_pwm_pins(PWM_ODD_ON,PWM_ODD_ON,PWM_OFF,PWM_OFF);
setup_power_pwm(PWM_CLOCK_DIV_128 |PWM_FREE_RUN,1,0,period,0,1,0);
//forward
output_B(0b01010000);

while(true)
{
// half speed
delay_ms(1000);
printf("\n\n\r Half");
move(5,FORWARD,5,FORWARD);
set_power_pwm0_duty(liLeftDuty);
set_power_pwm2_duty(liRightDuty);

//full speed
delay_ms(1000)
printf("\n\n\r Full");
move(10,FORWARD,10,FORWARD);
set_power_pwm0_duty(liLeftDuty);
set_power_pwm2_duty(liRightDuty);

}//while true


}//main()

////////////////////////////////////////////////////////////////////////////
//void move(int left_speed,int left_direction,
// int right_speed, int right_direction)
// this is used to set the speed and direction of the bot
// speed is a value for 0-10
// since this uses PWM for the motors and anything below ~40% duty is useless
// setting the speed to 1 will be ~40% duty and 0 will be off
//
// example: move(10,FORWARD,5,FORWARD);
void move(int left_speed,int left_direction, int right_speed, int right_direction)
{
int direction;
int16 baseline = 1460; // ~40%
int16 factor = 214; // ~ (16232 - 6600 )/ 10

if(left_speed > 10)
left_speed = 10;
if(right_speed > 10)
right_speed = 10;

//calc speed first and set pwm
if(left_speed == 0)
liLeftDuty = left_speed;
else
liLeftDuty = (left_speed * factor) + baseline;

if(right_speed == 0)
liRightDuty = right_speed;
else
liRIghtDuty = (right_speed * factor) + baseline;

}//move

[PCM programmer]

What's your compiler version ? CCS has this statement on their
versions page:

[Jim]

version 3.212.. thanks. I'll upgrade..