Pwm(Pulse Width Modulation) presentation
- 1. PWM Mode In Timer1 By: Habitamu Asimare EMBEDDED SYSTEMS PWM Mode In Timer1 1
- 2. PWM Concepts • Usages of PWM – Sound Output – Control of Motor – Dimming of LED • Key Words – Pulses – Period – Phase Correct PWM – Duty Cycle – Inverted and Non-Inverted • Points Discussed – PWM Timer 1 – Phase correct Timer 1 PWM Pulse Period 50% Duty Cycle Phase Correct PWM 22 PWM Mode In Timer1
- 3. PWM In Timer 1 Modes • There are five types of modes in fast PWM – Mode 5 (top = 0xFF) – Mode 6 (top = 0x1FF) – Mode 7 (top = 0x3FF) – Mode 14 (top = ICR1) – Mode 15 (top = OCR1A) Mode WGM13 WGM12 WGM11 WGM10 Timer/Mode of operation 5 0 1 0 1 Fast PWM, 8 bit 6 0 1 1 0 Fast PWM, 9 bit 7 0 1 1 1 Fast PWM, 10 bit 14 1 1 1 0 Fast PWM 15 1 1 1 1 Fast PWM In Inverted PWM COM1A1 and COM1A0 will be high In Non-Inverted PWM only COM1A1 is high 3 PWM Mode In Timer1
- 4. Phase Correct PWM mode • There are five phase correct PWM modes – Mode 1 – Mode 2 – Mode 3 – Mode 10 – Mode 11 Mode WGM13 WGM12 WGM11 WGM10 Timer/Mode of operation 1 0 0 0 1 PWM, phase correct, 8 bit 2 0 0 1 0 PWM, phase correct, 9 bit 3 0 0 1 1 PWM, phase correct,10 bit 10 1 0 1 0 PWM, phase correct 11 1 0 1 1 PWM, phase correct 4 4 PWM Mode In Timer1
- 5. Fast PWM & Phase Correct Fast PWM Phase Correct Non Inverted Inverted 5 5 PWM Mode In Timer1
- 6. Example 1 Solution • In Mode 5, WGM10 & WGM12 is high • There is no pre-scalar then only CS10 is high • It is non-inverted so, COM1A1 is high • The value of TCCR1A is 0x81 • The value of TCCR1B is 0x09 6 PWM Mode In Timer1
- 7. Example 2 • Then We have to calculate – OCR1A1 value from the formula non inverted mode, OCR1x = ((Top + 1)*duty_cylce/100)-1 = ((255+1)*75/100)-1 = 191 – TCCR1A = 0x81 – TCCR1B = 0x09 7 PWM Mode In Timer1 #include <avr/io.h> int main(void) { DDRD |= (1<<5); OCR1AH = 0; OCR1AL = 191; TCCR1A = 0X81; TCCR1B = 0X09; while (1); return 0; }
- 8. Example 3 – In mode 1, WGM10 is high – It is none inverted and COM1A1 is high – No pre-scalar and CS10 is high – The value of TCCR1A is 0x81 – The value of TCCR1B is 0x01 8 PWM Mode In Timer1
- 9. Example 4 – The value of TCCR1A is 0x91 – The value of TCCR1B is 0x01 – OCR1Ax = 191 9 PWM Mode In Timer1 #include <avr/io.h> int main(void) { DDRD |= (1<<5); OCR1AH = 0; OCR1AL = 191; TCCR1A = 0X91; TCCR1B = 0X01; while (1); return 0; }
- 10. Question? Thank You! 10 PWM Mode In Timer1