I have a code for finding the rpm of one system calling here as engine , the engine have a hall sensor output and I have tried the following Code
#define SERVO_MIN 2000
#define SERVO_MAX 4000
struct Pulse {
uint32_t last_toggle;
uint32_t width;
uint32_t width_prev;
uint32_t time_prev;
bool stateHigh = false;
uint32_t get_width() {
noInterrupts();
uint32_t width_copy = width;
interrupts();
return width_copy;
}
};
struct Engine {
uint16_t servoMin = 2000, servoMax = 4000;
uint16_t rpm_desired;
volatile Pulse pulse;
uint32_t get_rpm() {
cli();
uint32_t rpm_width = pulse.get_width();
sei();
return 12e7 / rpm_width;
}
};
Engine engine1,engine2;
void pin_initialization() {
// INT2
pinMode(19, INPUT_PULLUP);
// Input capture points
pinMode(49, INPUT_PULLUP);
pinMode(48, INPUT_PULLUP);
}
void timer4_initialization() {
cli();
TCCR4A = 0; TCCR4B = 0; TCCR4C = 0;
TCCR4A = B10101011;
TIMSK4 = B00100000;
TIFR4 = _BV(ICF4);
TCCR4B = B11011010;
OCR4A = 39999;
OCR4B = SERVO_MIN;//7
OCR4C = SERVO_MIN;//8
sei();
}
void timer5_initialization() {
cli();
TCCR5A = 0; TCCR5B = 0; TCCR5C = 0;
TCCR5A = B10101011;
TIMSK5 = B00100000;
TIFR5 = _BV(ICF5);
TCCR5B = B11011010;
OCR5A = 39999;
OCR5B = SERVO_MIN;//45
OCR5C = SERVO_MIN;//44
sei();
}
void timer3_initialization() {
TCCR3A = 0x00; TCCR3C = 0x00;
TCNT3 = 0x1FF; // from datasheet
TIFR3 = _BV(TOV3);
TIMSK3 = _BV(TOIE3); // overflow enable
TCCR3B = B00000010; // 8 prescaling
}
volatile uint32_t ovfCount = 0;
ISR(TIMER3_OVF_vect) {
ovfCount++;
}
void pulseWidthCalculator(Pulse *channel) {
unsigned char sreg;
sreg = SREG;
cli();
uint16_t tcnt3 = TCNT3;
uint32_t ovf_count = ovfCount;
SREG = sreg;
if (bit_is_set(TIFR3, TOV3) && tcnt3 < 16384) {
ovf_count++;
}
uint32_t time = ovf_count << 16 | tcnt3;
if (!channel->stateHigh) {
channel->stateHigh = true;
} else if ( channel->stateHigh) {
channel->width = time - channel->last_toggle;
channel->stateHigh = false;
}
channel->last_toggle = time;
sei();
}
void externalInterrputInitialization() {
EIFR = _BV(INTF2) ;
EICRA = 0; EICRB = 0;
EICRA = B00100000;
EIMSK = B00000100;
}
ISR(INT2_vect) {
pulseWidthCalculator(&engine1.pulse);
}
ISR(TIMER4_CAPT_vect) {
pulseWidthCalculator(&engine2.pulse);
}
ISR(TIMER5_CAPT_vect) {
// pulseWidthCalculator(&engine2.pulse);
}
void setup() {
Serial.begin(115200);
pin_initialization();
delayMicroseconds(10);
externalInterrputInitialization();
delayMicroseconds(10);
timer3_initialization();
delayMicroseconds(10);
timer4_initialization();
delayMicroseconds(10);
timer5_initialization();
delayMicroseconds(10);
}
void loop() {
Serial.print(engine1.get_rpm());
Serial.print("\t" );
Serial.println(engine2.get_rpm());
}
The same hall sensor output is given to the INT2 (pin #19) pin and ICP4(pin #49) and the results obtained is given below
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I have a feeling that the Noise canceller in the input capture pin is helping here, I would like to get help on
- How to make the interrupt values also correct
- What logical mistake am I making.
how to add the logic of noise cancelling to Interrupt subroutine code.
If I have to add 4/6 such engines what is the best option.
** with a function generator both INT and ICP are giving the correct result.
