Styjun

The goal of my application is to use an ATMEGA328P as the core of a Digital Direct Synthesis 400 Hertz sinusoidal generator. Pulses from the microprocessor are sent to the gates of four high-voltage N-MOSFET connected as a full H bridge. 16-bitTimer1 uses WGM mode 10 and commands the Northeast and Northwest MOSFET. 8-bitTimer0 and 8-bitTimer2 use mode 5 and command the Southeast and Southwest MOSFET respectively. I was able to generate the pulses with the correct widths but I failed to get them correctly synchronized. There is one or two clock slippage between the Timer1 pulses and the corresponding ones from Timer0 and Timer2.

I had no success when tried to compensate this delay by setting Timer0 and Timer2 initial counts.

#define CPU_FREQ 16000000UL
#define OUT_FREQ 400UL
#define SAMPLE_FREQ 40000UL
#define SAMPLE_COUNT SAMPLE_FREQ/OUT_FREQ/2
#define SAMPLE_MAX CPU_FREQ/SAMPLE_FREQ/2 - 1
#define TIMER0_MAX 255
#define TIMER2_MAX 255
#define TIMER0_DELAY 1
#define TIMER2_DELAY 1

void setupTimers() bit( PSRSYNC);
 setupTimer0();
 setupTimer1();
 setupTimer2();
 sei(); // enable global interrupts;
 GTCCR = 0; 


void setupTimer0() 
 // Waveform Generation Mode 5, PWM, Phase Correct
 // TOP = OCR0A, OCR1B updated at TOP, TOV1 Flag set on BOTTOM
 // Set OC0B on Compare Match when up-counting.
 // Clear OC0B on Compare Match when down-counting
 // Clock Source Mode 1, No prescaling
 // OCIE0B, OCIE0A, TOIE0 interrupts disaabled
 // No Force Output Compare A or B
 // TCNT0 initial count compensation for OCR0A as TOP delay

 TCCR0A = bit(COM0B1) 

void setupTimer1() bit(COM1B1) 

void setupTimer2() 
 // Waveform Generation Mode 5, PWM, Phase Correct
 // TOP = OCR0A, OCR1B updated at TOP, TOV1 Flag set on BOTTOM
 // Set OC0B on Compare Match when up-counting.
 // Clear OC0B on Compare Match when down-counting
 // Clock Source Mode 1, No prescaling
 // OCIE0B, OCIE0A, TOIE0 interrupts disaabled
 // No Force Output Compare A or B
 // TCNT2 initial count compensation for OCR2A as TOP delay

 TCCR2A = bit(COM2B1) 

Expected results: synchronized pulses
Actual results: non synchronized pulses

By trial and error I managed to find a combination of TIMER0_DELAY, TIMER1_DELAY and TIMER2_DELAY that solved my problem.