// ***************************************************************************
// File Name : servo.c
// Version : 1.0
// Description : Servo Motor Controller
// Using TIMER0 for Generating Servo PWM
// Target : PICJazz 16F690 Board
// Compiler : HITECT PICC-Lite Version 9.60PL1
// IDE : Microchip MPLAB IDE v8.00
// Programmer : PICKit2
// ***************************************************************************
#include <pic.h>
/* PIC Configuration Bit:
** INTIO - Using Internal RC No Clock
** WDTDIS - Wacthdog Timer Disable
** PWRTEN - Power Up Timer Enable
** MCLREN - Master Clear Enable
** UNPROTECT - Code Un-Protect
** UNPROTECT - Data EEPROM Read Un-Protect
** BORDIS - Borwn Out Detect Disable
** IESODIS - Internal External Switch Over Mode Disable
** FCMDIS - Monitor Clock Fail Safe Disable
*/
__CONFIG(INTIO & WDTDIS & PWRTEN & MCLREN & UNPROTECT \
& UNPROTECT & BORDIS & IESODIS & FCMDIS);
// Using Internal Clock of 8 Mhz
#define FOSC 8000000L
// Servo definition and variables
#define MAX_VALUE 200
#define CCW_ROTATION MAX_VALUE - 20
#define CW_ROTATION MAX_VALUE - 10
#define STOP_ROTATION MAX_VALUE
#define THRESHOLD_VALUE 50
unsigned char pulse_max=0;
unsigned char pulse_top=0;
unsigned char top_value = 0;
static void interrupt isr(void)
{
if(T0IF) { // TIMER0 Interrupt Flag
pulse_max++; // Pulse Max Increment
pulse_top++; // Pulse Top Increment
/* MAX_VALUE=200 turn off the pulse */
if (pulse_max >= MAX_VALUE) {
pulse_max=0;
pulse_top=0;
RC2=0; // Turn off RC2
}
/* top_value = MAX_VALUE - n, n=10: 10 x 0.1ms = 1.0ms, n=20: 20 x 0.1ms = 2.0ms */
/* 2ms -> CCW Rotation, 1ms -> CW Rotation */
if (pulse_top == top_value) {
RC2=1; // Turn On RC2
}
TMR0 = 156; // Initial Value for 0.1ms Interrupt
T0IF = 0; // Clear TIMER0 interrupt flag
}
}
void main(void)
{
unsigned char ldr_left;
unsigned char ldr_right;
int ldr_diff;
OSCCON=0x70; // Select 8 Mhz internal clock
/* Initial Port Used */
TRISC = 0x03; // Set RC0 and RC1 as input others as Output
ANSEL = 0x30; // Set PORT AN4 and AN5 as analog input
ANSELH = 0x00; // Set PORT AN8 to AN11 as Digital I/O
PORTC = 0x00; // Turn Off all PORTC
/* Init Servo Pulse */
pulse_max=0;
pulse_top=0;
top_value = MAX_VALUE; // top_value = MAX_VALUE: Servo Motor Stop
/* Initial ADC */
ADCON1=0b00110000; // Select the FRC for 8 Mhz
/* Init TIMER0: Period: Fosc/4 x Prescaler x TMR0
0.0005 ms x 2 * 100 = 0.1 ms */
OPTION = 0b00000000; // 1:2 Prescaller
TMR0=156; // Interupt every 0.1 ms
T0IE = 1; // Enable interrupt on TMR0 overflow
GIE = 1; // Global interrupt enable
for(;;) {
/* Read the ADC here */
ADCON0=0b00010001; // select left justify result. ADC port channel AN4
GODONE=1; // initiate conversion on the channel 4
while(GODONE) continue; // Wait for ldr_left conversion done
ldr_left=ADRESH; // Read 8 bits MSB, Ignore 2 bits LSB in ADRESL
ADCON0=0b00010101; // select left justify result. ADC port channel AN5
GODONE=1; // initiate conversion on the channel 5
while(GODONE) continue; // Wait for ldr_right conversion done
ldr_right=ADRESH; // Read 8 bits MSB, Ignore 2 bits LSB in ADRESL
/* Get the different */
ldr_diff=ldr_left - ldr_right;
if ((ldr_diff >= -THRESHOLD_VALUE) && (ldr_diff <= THRESHOLD_VALUE)) {
top_value = MAX_VALUE; // Stop the Servo Motor
} else {
if (ldr_diff > THRESHOLD_VALUE) {
top_value = CCW_ROTATION; // Counterclockwise Rotation
} else {
top_value = CW_ROTATION; // Clockwise Rotation
}
}
}
}
/* EOF: servo.c */