From ec8defaa998f8c6f5b9cf2cd7624436bf0cd8e73 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Mon, 14 Oct 2013 11:24:51 +0200
Subject: [PATCH] added simple IR receiver burst recording

---
 src/main.c | 124 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 84 insertions(+), 40 deletions(-)

diff --git a/src/main.c b/src/main.c
index 549d82f..dd4b4fa 100644
--- a/src/main.c
+++ b/src/main.c
@@ -10,22 +10,37 @@
 #include "uart.h"
 
 /* global variables */
-volatile uint8_t pwr_ok;
-volatile uint8_t fan;
-volatile uint16_t tachometer = 0;
-volatile uint8_t timer2_ovf = 0;
+volatile uint8_t pwr_ok; /* is power ok */
+volatile uint8_t fan; /* fan signal state, to measure tachometer */
+volatile uint8_t timer2_ovf = 0; /* to measure fan speed using timer 2 */
+static const uint16_t TIMER2_PRESCALE[8] = {0,1,8,32,64,128,256,1024}; /* timer 2 CS2[2:0] values */
+volatile uint16_t tachometer = 0; /* the tachometer time (from timer) */
+volatile uint8_t ir; /* IR signal state, to measure IR code */
+volatile uint8_t pulse_i = 1; /* pulse index */
+# define PULSE_MAX 64 /* maximum number of pulses to save */
+volatile uint16_t pulse[PULSE_MAX]; /* pulse times (from timer) */
 
-const uint16_t TIMER2_PRESCALE[8] = {0,1,8,32,64,128,256,1024};
 
-/* PWR_OK interrupt */
+/* power ok interrupt */
 ISR(PCINT0_vect) { /* PCI0 Interrupt Vector for PCINT[7:0] */
 	if (pwr_ok!=(PINB&(1<<PWR_OK))) { /* did the PWR_OK pin state changed */
 		pwr_ok = PINB&(1<<PWR_OK); /* save new state */
 		if (pwr_ok) {
+			/* switch timer 2 on to start measuring the fan speed */
 			puts("power ok");
 		} else {
 			puts("power ko");
 		}
+	} else if (ir!=(PINB&(1<<IR))) { /* did the IR pin state changed */
+		ir = PINB&(1<<IR); /* save new state */
+		if (pulse_i>0) { /* save pulse, except the first */
+			pulse[pulse_i-1] = TCNT1;
+			pulse[pulse_i] = 0;
+		}
+		if (pulse_i<PULSE_MAX-1) { /* prepare to save next pulse */
+			pulse_i++;
+		}
+		TCNT1 = 0; /* clear timer 1 */
 	}
 }
 
@@ -33,18 +48,26 @@ ISR(PCINT0_vect) { /* PCI0 Interrupt Vector for PCINT[7:0] */
 ISR(PCINT1_vect) { /* PCI0 Interrupt Vector for PCINT[14:8] */
 	if (fan!=(PINC&(1<<FAN))) { /* did the FAN pin state changed */
 		fan = PINC&(1<<FAN); /* save new state */
-		if (fan) {
-			tachometer = timer2_ovf*256+TCNT2; /* save time */
+		if (fan) { /* only react to rising edge */
+			tachometer = (uint16_t)(timer2_ovf<<8)+TCNT2; /* save time */
 			TCNT2 = 0; /* reset timer 2 */
-			timer2_ovf = 0; /* reset timer 2 overflow counter */
+			timer2_ovf = 0; /* reset timer 2 */
 		}
 	}
 }
 
-/* timer 2 interrupt used to measure fan tachometer */
-ISR(TIMER2_OVF_vect) { /* timer 2 overflow interrupt verctor */
-	if(pwr_ok) { /* only measure tachometer if power is ok */
-		timer2_ovf++; /* increase time 2 overflow counter */
+/* timer 2 interrupt used to measure fan speed based on tachometer */
+ISR(TIMER2_OVF_vect) { /* timer 2 overflow interrupt vector */
+	if (timer2_ovf<0xff) { /* prevent overflow */
+		timer2_ovf++; /* increase tachometer counter */
+	}
+}
+
+/* timer 1 interrupt used to measure IR pulse */
+ISR(TIMER1_COMPA_vect) { /* timer 1 OCR1A match interrupt vector */
+	if (pulse_i>0) {
+		pulse_i = 0;
+		OCR0A = ~OCR0A;
 	}
 }
 
@@ -59,9 +82,21 @@ static void ioinit(void)
 	PCICR |= (1<<PCIE0); /* enable interrupt for PCINT[7:0] */
 	PCMSK0 |= (1<<PCINT1); /* enable interrupt for PCINT1 */
 
-	/* configure peripherals */
-	DDRB &= ~(1<<IR); /* IR receiver is input */
-
+	/* configure LED (on PD6/OC0A) */
+	DDRD |= (1<<LED); /* LED is output */
+	/* use timer 1 to produce a PWM */
+	/* use phase correct PWM mode (because fast PWM is always on for at least 1 cycle) */
+	TCCR0A &= ~(1<<WGM01);
+	TCCR0A |= (1<<WGM00);
+	TCCR0B &= ~(1<<WGM02);
+	/* /64 prescale timer */
+	TCCR0B &= ~(1<<CS02);
+	TCCR0B |= (1<<CS01)|(1<<CS00);
+	/* clear on match, because the pin is used as sink */
+	TCCR0A |= (1<<COM0A1)|(1<<COM0A0);
+	/* start with LED on */
+	OCR0A = 0xff;
+	
 	/* configure FAN */
 	DDRC &= ~(1<<FAN); /* FAN (PC5/PCINT13) is input */
 	fan = PINC&(1<<FAN); /* save state */
@@ -72,12 +107,30 @@ static void ioinit(void)
 	/* use normal mode */
 	TCCR2A &= ~((1<<WGM20)|(1<<WGM21));
 	TCCR2B &= ~(1<<WGM22);
-	/* /256 prescale timer */
-	TCCR2B |= (1<<CS22)|(1<<CS21);
-	TCCR2B &= ~(1<<CS20);
+	/* clock/64 prescaler */
+	TCCR2B |= (1<<CS22);
+	TCCR2B &= ~((1<<CS21)|(1<<CS20));
 	TIFR2 &= ~(1<<TOV2); /* clear timer 2 overflow interrupt flag */
 	TIMSK2 |= (1<<TOIE2); /* enable timer 2 overflow interrupt */
 
+	/* configure IR receiver */
+	DDRB &= ~(1<<IR); /* IR (PB0/PCINT0) receiver is input */
+	ir = PINB&(1<<IR); /* save state */
+	PCIFR &= ~(1<<PCIF0); /* clear interrupt flag */
+	PCICR |= (1<<PCIE0); /* enable interrupt for PCINT[7:0] */
+	PCMSK0 |= (1<<PCINT0); /* enable interrupt for PCINT0 */
+	/* use timer 1 to measure IR pulse */
+	/* use CTC mode */
+	TCCR1A &= ~((1<<WGM10)|(1<<WGM11));
+	TCCR1B |= (1<<WGM12);
+	TCCR1B &= ~(1<<WGM13);
+	/* clock/8 prescaler, offers most precision for 15ms (up to 28.5ms) */
+	TCCR1B |= (1<<CS11);
+	TCCR1B &= ~((1<<CS12)|(1<<CS10));
+	OCR1A = (uint32_t)(15*F_CPU)/(1000*8); /* set clear time to 15 ms (no IR toggle should be longer) */
+	TIFR1 &= ~(1<<OCF1A); /* clear timer 1 overflow interrupt flag */
+	TIMSK1 |= (1<<OCIE1A); /* enable timer 1 overflow interrupt */
+
 	/* configure channels (used for powering LEDs using an nMOS) */
 	DDRC |= (1<<CH1_1)|(1<<CH1_2)|(1<<CH1_3)|(1<<CH1_4)|(1<<CH1_5); /* CH1_x is output */
 	PORTC &= ~((1<<CH1_1)|(1<<CH1_2)|(1<<CH1_3)|(1<<CH1_4)|(1<<CH1_5)); /* switch off CH1_x */
@@ -89,20 +142,6 @@ static void ioinit(void)
 	stdout = &uart_output;
 	stdin  = &uart_input;
 
-	/* configure LED (on PD6/OC0A) */
-	DDRD |= (1<<LED); /* LED is output */
-	/* use phase correct PWM mode (because fast PWM is always on for at least 1 cycle) */
-	TCCR0A &= ~(1<<WGM01);
-	TCCR0A |= (1<<WGM00);
-	TCCR0B &= ~(1<<WGM02);
-	/* /64 prescale timer */
-	TCCR0B &= ~(1<<CS02);
-	TCCR0B |= (1<<CS01)|(1<<CS00);
-	/* clear on match, because the pin is used as sink */
-	TCCR0A |= (1<<COM0A1)|(1<<COM0A0);
-	/* start with LED on */
-	OCR0A = 0xff;
-
 	sei(); /* enable interrupts */
 }
 
@@ -112,7 +151,7 @@ int main(void)
 
 	char input;
 
-	puts("Hello world!");
+	puts("LED dimmer up & running");
 	_delay_ms(1000);
 	while(1) {
 		input = getchar();
@@ -238,24 +277,29 @@ int main(void)
 				if (OCR0A>0) {
 					OCR0A--;
 				}
-				printf("decreasing LED: %d\n",OCR0A);
+				printf("decreasing LED: %u\n",OCR0A);
 				break;
 			case '+':
 				if (OCR0A<0xff) {
 					OCR0A++;
 				}
-				printf("increasing LED: %d\n",OCR0A);
+				printf("increasing LED: %u\n",OCR0A);
 				break;
 			case 't':
 				if (tachometer) {
 					uint16_t prescale = TIMER2_PRESCALE[TCCR2B&((1<<CS22)|(1<<CS21)|(1<<CS20))];
 					if (prescale) {
-						uint32_t speed = ((60*F_CPU)/(prescale*(uint32_t)tachometer))/2;
-						printf("fan speed: %lurpm\n",speed);
-						printf("fan speed: %lurpm\n",timer2_ovf);
+						if (timer2_ovf<0xff) {
+							uint32_t speed = ((60*F_CPU)/(prescale*(uint32_t)tachometer))/2; /* calculate speed. 2 pulses per revolution */
+							printf("fan speed: %lurpm\n",speed);
+						} else {
+							printf("fan off (or not detected)\n");
+						}
+					} else {
+						printf("fan speed measurement not started\n");
 					}
 				} else {
-					printf("fan off or too slow\n");
+					printf("fan off (or not detected)\n");
 				}
 				break;
 		}