PIC18
PIC18, MPLAB X IDE, XC8, PWM, buzzer
CoyoteUgly
2018. 9. 13. 11:31
PIC18, MPLAB X IDE, XC8, PWM, buzzer
4MHz clock을 통해 Timer2에 4KHz pwm 을 테스트하였습니다.
0. 참고 사항
1. HW 연결
2. 소스 설명
full 소스는 아래 github를 통해 확인하세요.
Period = 4 * TOSC * (PR2 + 1) * (TMR2 Prescale Value)
= 4 * 4 * (249 + 1) * 1
= 16 * 250
= 4000Hz
Duty Cycle = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value)
= 10bit cycle
Delay = 4 * TOSC * (PWM1CON<6:0>)
void pwm_Init(unsigned char period){
TRISC2 = 0; // RC2 output
/* CCP PWM mode */
CCP1CON = 0X3C;
// CCP1CON REGISTER (ECCP1 MODULE, 40/44-PIN DEVICES)
// P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0
// 0 0 1 1 1 1 0 0
// P1M1:P1M0: Enhanced PWM Output Configuration bits
// 00 = Single output: P1A modulated; P1B, P1C, P1D assigned as port pins
// DC1B1:DC1B0: PWM Duty Cycle bit 1 and bit 0
// CCP1M3:CCP1M0: Enhanced CCP Mode Select bits
// 1100 = PWM mode; P1A, P1C active-high; P1B, P1D active-high
/* Timer2 configuration */
PR2 = period; // configure timer2 period
T2CON=0x04;
// T2CON: TIMER2 CONTROL REGISTER
// - T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0
// 0 0 0 0 0 1 0 0
// Unimplemented: Read as ?0?
// T2OUTPS3:T2OUTPS0: Timer2 Output Postscale Select bits
// TMR2ON: Timer2 On bit
// T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
// 00 = Prescaler is 1
}
void pwm_setDuty(unsigned int dutycycle)
{
CCPR1L = dutycycle>>2; // PWM duty cycle - first 8-bits (MSb)
CCP1CON &= 0xCF; // 5,4 bits zeroed (DC1B1:DC1B0 = 00)
CCP1CON |= ((dutycycle<<4) & 0x30); // PWM duty cycle - last 2-bits (LSb) in CCP1CON 5,4 bits
}
void main(void)
{
pwm_Init(249);
pwm_setDuty(duty); // 0 ~ 1023 ... }
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3. 소스
4. 결과
잘 동작하네요
