void pwm_init(void)
// Initialize the PWM module for controlling a DC motor.
{
// Initialize the pwm frequency divider value.
pwm_div = registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO);
// Set EN_A (PD2) and EN_B (PD3) to low.
PORTD &= ~((1<<PD2) | (1<<PD3));
// Set SMPLn_B (PD4) and SMPLn_A (PD7) to high.
PORTD |= ((1<<PD4) | (1<<PD7));
// Enable PD2, PD3, PD4 and PD7 as outputs.
DDRD |= ((1<<DDD2) | (1<<DDD3) | (1<<DDD4) | (1<<DDD7));
// Set PWM_A (PB1/OC1A) and PWM_B (PB2/OC1B) are low.
PORTB &= ~((1<<PB1) | (1<<PB2));
// Enable PB1/OC1A and PB2/OC1B as outputs.
DDRB |= ((1<<DDB1) | (1<<DDB2));
// Reset the timer1 configuration.
TCNT1 = 0; // Timer/Counter1 1,2,...X
TCCR1A = 0; // Timer/Counter1 Control Register A
TCCR1B = 0; // Timer/Counter1 Control Register B
TCCR1C = 0; // Timer/Counter1 Control Register C
TIMSK1 = 0; // Timer/Counter1 Interrupt Mask
// Set timer top value.
ICR1 = PWM_TOP_VALUE(pwm_div); //Input Capture Register1
// Set the PWM duty cycle to zero.
OCR1A = 0; //Output Compare Register1 A
OCR1B = 0; //Output Compare Register1 B
// Configure timer 1 for PWM, Phase and Frequency Correct operation, but leave outputs disabled.
TCCR1A = (0<<COM1A1) | (0<<COM1A0) | // Disable OC1A output.
(0<<COM1B1) | (0<<COM1B0) | // Disable OC1B output.
(0<<WGM11) | (0<<WGM10); // PWM, Phase and Frequency Correct, TOP = ICR1
TCCR1B = (0<<ICNC1) | (0<<ICES1) | // Input on ICP1 disabled.
(1<<WGM13) | (0<<WGM12) | // PWM, Phase and Frequency Correct, TOP = ICR1
(0<<CS12) | (0<<CS11) | (1<<CS10); // No prescaling.
// Update the pwm values.
registers_write_byte(REG_PWM_DIRA, 0);
registers_write_byte(REG_PWM_DIRB, 0);
}
void pwm_init(void)
// Initialize the PWM module for controlling a DC motor.
{
// Initialize the pwm frequency divider value.
pwm_div = registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO);
TCCR1A = 0;
asm("nop");
asm("nop");
asm("nop");
// Set PB1/OC1A and PB2/OC1B to low.
PORTB &= ~((1<<PB1) | (1<<PB2));
// Enable PB1/OC1A and PB2/OC1B as outputs.
DDRB |= ((1<<DDB1) | (1<<DDB2));
// Reset the timer1 configuration.
TCNT1 = 0;
TCCR1A = 0;
TCCR1B = 0;
TCCR1C = 0;
TIMSK1 = 0;
// Set timer top value.
ICR1 = PWM_TOP_VALUE(pwm_div);
// Set the PWM duty cycle to zero.
OCR1A = 0;
OCR1B = 0;
// Configure timer 1 for PWM, Phase and Frequency Correct operation, but leave outputs disabled.
TCCR1A = (0<<COM1A1) | (0<<COM1A0) | // Disable OC1A output.
(0<<COM1B1) | (0<<COM1B0) | // Disable OC1B output.
(0<<WGM11) | (0<<WGM10); // PWM, Phase and Frequency Correct, TOP = ICR1
TCCR1B = (0<<ICNC1) | (0<<ICES1) | // Input on ICP1 disabled.
(1<<WGM13) | (0<<WGM12) | // PWM, Phase and Frequency Correct, TOP = ICR1
(0<<CS12) | (0<<CS11) | (1<<CS10); // No prescaling.
// Update the pwm values.
registers_write_byte(REG_PWM_DIRA, 0);
registers_write_byte(REG_PWM_DIRB, 0);
}
void pwm_update(uint16_t position, int16_t pwm)
// Update the PWM signal being sent to the motor. The PWM value should be
// a signed integer in the range of -255 to -1 for clockwise movement,
// 1 to 255 for counter-clockwise movement or zero to stop all movement.
// This function provides a sanity check against the servo position and
// will prevent the servo from being driven past a minimum and maximum
// position.
{
uint8_t pwm_width;
uint16_t min_position;
uint16_t max_position;
// Quick check to see if the frequency divider changed. If so we need to
// configure a new top value for timer/counter1. This value should only
// change infrequently so we aren't too elegant in how we handle updating
// the value. However, we need to be careful that we don't configure the
// top to a value lower than the counter and compare values.
if (registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO) != pwm_div)
{
// Hold EN_A (PD2) and EN_B (PD3) low.
PORTD &= ~((1<<PD2) | (1<<PD3));
// Give the H-bridge time to respond to the above, failure to do so or to wait long
// enough will result in brownouts as the power is "crowbarred" to varying extents.
// The delay required is also dependant on factors which may affect the speed with
// which the MOSFETs can respond, such as the impedance of the motor, the supply
// voltage, etc.
//
// Experiments (with an "MG995") have shown that 5microseconds should be sufficient
// for most purposes.
//
delay_loop(DELAYLOOP);
// Disable OC1A and OC1B outputs.
TCCR1A &= ~((1<<COM1A1) | (1<<COM1A0));
TCCR1A &= ~((1<<COM1B1) | (1<<COM1B0));
// Make sure that PWM_A (PB1/OC1A) and PWM_B (PB2/OC1B) are held low.
PORTB &= ~((1<<PB1) | (1<<PB2));
// Reset the A and B direction flags.
pwm_a = 0;
pwm_b = 0;
// Update the pwm frequency divider value.
pwm_div = registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO);
// Update the timer top value.
ICR1 = PWM_TOP_VALUE(pwm_div);
// Reset the counter and compare values to prevent problems with the new top value.
TCNT1 = 0;
OCR1A = 0;
OCR1B = 0;
}
// Are we reversing the seek sense?
if (registers_read_byte(REG_REVERSE_SEEK) != 0)
{
// Yes. Swap the minimum and maximum position.
// Get the minimum and maximum seek position.
min_position = registers_read_word(REG_MAX_SEEK_HI, REG_MAX_SEEK_LO);
max_position = registers_read_word(REG_MIN_SEEK_HI, REG_MIN_SEEK_LO);
// Make sure these values are sane 10-bit values.
if (min_position > MAX_POSITION) min_position = MAX_POSITION;
if (max_position > MAX_POSITION) max_position = MAX_POSITION;
// Adjust the values because of the reverse sense.
min_position = MAX_POSITION - min_position;
max_position = MAX_POSITION - max_position;
}
else
{
// No. Use the minimum and maximum position as is.
// Get the minimum and maximum seek position.
min_position = registers_read_word(REG_MIN_SEEK_HI, REG_MIN_SEEK_LO);
max_position = registers_read_word(REG_MAX_SEEK_HI, REG_MAX_SEEK_LO);
// Make sure these values are sane 10-bit values.
if (min_position > MAX_POSITION) min_position = MAX_POSITION;
if (max_position > MAX_POSITION) max_position = MAX_POSITION;
}
// Disable clockwise movements when position is below the minimum position.
if ((position < min_position) && (pwm < 0)) pwm = 0;
// Disable counter-clockwise movements when position is above the maximum position.
if ((position > max_position) && (pwm > 0)) pwm = 0;
// Determine if PWM is disabled in the registers.
if (!(registers_read_byte(REG_FLAGS_LO) & (1<<FLAGS_LO_PWM_ENABLED))) pwm = 0;
// Determine direction of servo movement or stop.
if (pwm < 0)
{
// Less than zero. Turn clockwise.
// Get the PWM width from the PWM value.
pwm_width = (uint8_t) -pwm;
// Turn clockwise.
#if SWAP_PWM_DIRECTION_ENABLED
pwm_dir_b(pwm_width);
#else
pwm_dir_a(pwm_width);
#endif
}
else if (pwm > 0)
{
// More than zero. Turn counter-clockwise.
// Get the PWM width from the PWM value.
pwm_width = (uint8_t) pwm;
// Turn counter-clockwise.
#if SWAP_PWM_DIRECTION_ENABLED
pwm_dir_a(pwm_width);
#else
pwm_dir_b(pwm_width);
#endif
}
else
{
// Stop all PWM activity to the motor.
pwm_stop();
}
}
void pwm_update(uint16_t position, int16_t pwm)
// Update the PWM signal being sent to the motor. The PWM value should be
// a signed integer in the range of -255 to -1 for clockwise movement,
// 1 to 255 for counter-clockwise movement or zero to stop all movement.
// This function provides a sanity check against the servo position and
// will prevent the servo from being driven past a minimum and maximum
// position.
{
uint8_t pwm_width;
uint16_t min_position;
uint16_t max_position;
// Quick check to see if the frequency divider changed. If so we need to
// configure a new top value for timer/counter1. This value should only
// change infrequently so we aren't too elegant in how we handle updating
// the value. However, we need to be careful that we don't configure the
// top to a value lower than the counter and compare values.
if (registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO) != pwm_div)
{
// Disable OC1A and OC1B outputs.
TCCR1A &= ~((1<<COM1A1) | (1<<COM1A0));
TCCR1A &= ~((1<<COM1B1) | (1<<COM1B0));
// Clear PB1 and PB2.
PORTB &= ~((1<<PB1) | (1<<PB2));
delay_loop(DELAYLOOP);
// Reset the A and B direction flags.
pwm_a = 0;
pwm_b = 0;
// Update the pwm frequency divider value.
pwm_div = registers_read_word(REG_PWM_FREQ_DIVIDER_HI, REG_PWM_FREQ_DIVIDER_LO);
// Update the timer top value.
ICR1 = PWM_TOP_VALUE(pwm_div);
// Reset the counter and compare values to prevent problems with the new top value.
TCNT1 = 0;
OCR1A = 0;
OCR1B = 0;
}
// Are we reversing the seek sense?
if (registers_read_byte(REG_REVERSE_SEEK) != 0)
{
// Yes. Swap the minimum and maximum position.
// Get the minimum and maximum seek position.
min_position = registers_read_word(REG_MAX_SEEK_HI, REG_MAX_SEEK_LO);
max_position = registers_read_word(REG_MIN_SEEK_HI, REG_MIN_SEEK_LO);
// Make sure these values are sane 10-bit values.
if (min_position > 0x3ff) min_position = 0x3ff;
if (max_position > 0x3ff) max_position = 0x3ff;
// Adjust the values because of the reverse sense.
min_position = 0x3ff - min_position;
max_position = 0x3ff - max_position;
}
else
{
// No. Use the minimum and maximum position as is.
// Get the minimum and maximum seek position.
min_position = registers_read_word(REG_MIN_SEEK_HI, REG_MIN_SEEK_LO);
max_position = registers_read_word(REG_MAX_SEEK_HI, REG_MAX_SEEK_LO);
// Make sure these values are sane 10-bit values.
if (min_position > 0x3ff) min_position = 0x3ff;
if (max_position > 0x3ff) max_position = 0x3ff;
}
// Disable clockwise movements when position is below the minimum position.
if ((position < min_position) && (pwm < 0)) pwm = 0;
// Disable counter-clockwise movements when position is above the maximum position.
if ((position > max_position) && (pwm > 0)) pwm = 0;
// Determine if PWM is disabled in the registers.
if (!(registers_read_byte(REG_FLAGS_LO) & (1<<FLAGS_LO_PWM_ENABLED))) pwm = 0;
// Determine direction of servo movement or stop.
if (pwm < 0)
{
// Less than zero. Turn clockwise.
// Get the PWM width from the PWM value.
pwm_width = (uint8_t) -pwm;
// Turn clockwise.
#if SWAP_PWM_DIRECTION_ENABLED
pwm_dir_a(pwm_width);
#else
pwm_dir_b(pwm_width);
#endif
}
else if (pwm > 0)
{
// More than zero. Turn counter-clockwise.
// Get the PWM width from the PWM value.
pwm_width = (uint8_t) pwm;
// Turn counter-clockwise.
#if SWAP_PWM_DIRECTION_ENABLED
pwm_dir_b(pwm_width);
#else
pwm_dir_a(pwm_width);
#endif
}
else
{
// Stop all PWM activity to the motor.
pwm_stop();
}
}
