cdi_tester.ino

//	CDI tester - a pulse coil emulator
//	(c) 2019 Chris Kelley : technerdchris@gmail.com
//	License: SiYGR : Share if You Get Rich : If you use this and get rich, hook a brother up.
//	see https://electronics.stackexchange.com/questions/452219/
const char version[8]= {"v0.1"};
const char today[15] = {"2019 AUG 9"};
// LED connected to digital pin 13
#define LED_PIN 13
#define WHT_PIN 7
#define RED_PIN 6
#define POT_PIN 2

//	text buffer for Serial.println()
char text[80];

const int SPIKE = 100;	//	how wide the + and - pulses are in uSec
int pot_adc;
int last_pot_adc;

//	rpm will be integer divided by 50
int rpm;
int dwell;
long wait;
#define RPM_MIN 950
#define RPM_MAX 9000
#define ANALOG_READ_DELAY 100

void setup() {
	Serial.begin(9600); // open the serial port at 9600 bps
	Serial.println("---------------------------------");
	sprintf(text,"%s %s", version, today);
	Serial.println(text);
	
	pinMode(WHT_PIN, OUTPUT);
	pinMode(RED_PIN, OUTPUT);

	digitalWrite(WHT_PIN, HIGH);
	digitalWrite(RED_PIN, HIGH);
	
	pot_adc = analogRead(POT_PIN);
	sprintf(text,"... pot ADC %u", pot_adc);
	Serial.println(text);
	rpm = map(pot_adc, 0, 1023, RPM_MIN, RPM_MAX);
	setRpm();
}

int idx = 1;
void loop() {
	last_pot_adc = pot_adc;

	pot_adc = analogRead(POT_PIN);	//	this takes 0.1 mSec or 100 uSec

	int delta = pot_adc - last_pot_adc;
	if( delta < 0 )
		delta = -delta;
	if( delta > 2 ){
		sprintf(text,"... rpm changing detected\n last_pot_adc = %d\n      pot_adc = %d", last_pot_adc, pot_adc);
		Serial.println(text);
		delay(200);

		int temp = analogRead(POT_PIN);
		while( abs(pot_adc - temp) > 25 ) {
			sprintf(text,"... pot is changing ADC %d", temp);
			Serial.println(text);
			delay(200);
			pot_adc = temp;
			temp = analogRead(POT_PIN);
		}
		// pot_adc = analogRead(POT_PIN);
		//	convert range of 10 bit ADC to defined RPM range
		rpm = map(pot_adc, 0, 1023, RPM_MIN, RPM_MAX);
		setRpm();
	}
	//	high pulse
	digitalWrite(RED_PIN, LOW);		//	delays 1-2 uSec
	delayMicroseconds(SPIKE);
	digitalWrite(RED_PIN, HIGH);

	//	dwell
	delayMicroseconds(dwell);

	//	low pulse
	digitalWrite(WHT_PIN, LOW);
	delayMicroseconds(SPIKE);
	digitalWrite(WHT_PIN, HIGH);
	
	delayMicroseconds(wait);

	idx++;
	if( idx % 100 == 0 ){
		idx=0;
		Serial.println(".");
	}
}

//	MAGIC NUMBER ALERT: the pickup is 26° of the 360° rotation: there will be 26/360 implemented.
//	To calculate rpm to period and dwell, here's the human equation:
//	RPM		RPM -> Hz								Hz -> period (uSec)						period -> pulsewidth/dwell (uSec)
//			hz = rpm/60								period = 1/rpm*10,000					dwell = period * 26 / 360
//	1000	16.667									60.000									4333
//	........ now start to optimize for 32 bit INT maths ............	
//	RPM		pd1 = RPM/100		pd2 = 60,000/pd1	period = pd2*10		dw1 = period / 360	dwell = dw1*26
//	1000	10					6000				60000				167					4342	ERR = 8.8  uSec
//	7700	77					 779				 7790				 22					 572	ERR = 9.25 uSec
//	........ better optimize for 32 bit INT maths ............	
//	RPM		pd1 = RPM/50		pd2 = 12,000/pd1	period = pd2*100	dw1 = period / 36	dwell = (dw1*26)/10
//	1000	20					600					60000				1667				4334	ERR = 0.80  uSec
//	5200	104					115					11500				 319				 829	ERR = -4.31 uSec
//	7700	154					 78					 7800				 217				 564	ERR = 1.25  uSec
//	........ best optimize for 32 bit INT maths ............	
//	RPM		pd1 = RPM/50		pd2 = 24,000/pd1	period = pd2*50		dw1 = period / 36	dwell = (dw1*26)/10
//	1000	20					1200				60000				1667				4334	ERR = 0.80 uSec
//	5200	104					 231				11550				 321				 835	ERR = 1.69 uSec
//	7700	154					 156				 7800				 217				 564	ERR = 1.25 uSec
void setRpm(){
	sprintf(text,"========== %s() ============\nrpm was set to %d", __FUNCTION__, rpm);
	Serial.println(text);
	//	pd1 = RPM/50		pd2 = 24,000/pd1	period = pd2*50		dw1 = period / 36	dwell = (dw1*26)/10
	long period = rpm/50;
	sprintf(text,"line %d:long period = rpm/50 = %ld", __LINE__, period);
	Serial.println(text);

	period = 24000/period;
	sprintf(text,"line %d:period = 24000/period = %ld", __LINE__, period);
	Serial.println(text);

	period = period*50;
	sprintf(text,"line %d:period = period*50 = %ld", __LINE__, period);
	Serial.println(text);

	dwell = period/36;
	sprintf(text,"line %d:dwell = period/36 = %d", __LINE__, dwell);
	Serial.println(text);

	dwell = dwell*26;
	sprintf(text,"line %d:dwell = dwell*26 = %d", __LINE__, dwell);
	Serial.println(text);

	dwell = dwell/10;
	sprintf(text,"line %d:dwell = dwell/10 = %d", __LINE__, dwell);
	Serial.println(text);

	wait = period - dwell - ANALOG_READ_DELAY;
	sprintf(text,"line %d: wait = period - dwell - ANALOG_READ_DELAY = %ld", __LINE__, wait);
	Serial.println(text);

	sprintf(text,"==== LEAVING %s() ====", __FUNCTION__);
	Serial.println(text);
}