From 7b1287afaf92e0971d9d693baed2f1524aed4569 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Tue, 6 Jan 2015 17:52:22 +0100
Subject: [PATCH] add timer 1 measurement

---
 firmware/main.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/firmware/main.c b/firmware/main.c
index e1d4df8..1af7e2e 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -31,6 +31,10 @@
 
 /* variables */
 volatile uint8_t state_portD; // the state of port D
+volatile bool scale_on = false; // is the scale on (based on the SCALE_ON PIN)
+volatile bool pwm_high = false; // is the PWM for the last weight measurement high
+volatile bool measurement_flag = false; // is a PWM  measurement value ready
+volatile uint16_t measurement_value = 0; // the PWM measurement value from the timer
 
 /* switch off LED */
 void led_off(void)
@@ -57,8 +61,10 @@ ISR(PCINT2_vect)
 {
 	if ((state_portD&(1<<SCALE_ON))!=(PIND&(1<<SCALE_ON))) { // scale on state changed
 		if (PIND&(1<<SCALE_ON)) {
+			scale_on = true;
 			led_on();
 		} else {
+			scale_on = false;
 			led_off();
 		}
 	}
@@ -70,10 +76,17 @@ ISR(PCINT2_vect)
  */
 ISR(ANALOG_COMP_vect)
 {
-	if (ACSR&(1<<ACO)) { // PWM high
-		led_on();
-	} else { // PWM low
-		led_off();
+	if (scale_on && !measurement_flag) { // only save value if scale is on and previous value is read
+		measurement_value = TCNT1; // save value
+		TCNT1 = 0; // reset timer		
+		if (ACSR&(1<<ACO)) { // PWM raising edge
+			pwm_high = false;
+			led_on();
+		} else { // PWM falling edge
+			pwm_high = true;
+			led_off();
+		}
+		measurement_flag = true; // signal new value is ready
 	}
 }
 
@@ -114,11 +127,15 @@ void io_init(void)
 	ACSR &= ~(1<<ACD); // enable analog comparator (should be per default)
 	ACSR &= ~(1<<ACBG); // use AIN0 as positiv input (should be per default)
 	ACSR |= (1<<ACI); // clear analog comparator interrup flag
-	ACSR |= (1<<ACIC); // enable analog comparator input capture (on timer 1)
 	ACSR &= ~((1<<ACIS1)|(1<<ACIS0)); // comparator interrupt on output toggle
 	DIDR1 |= ((1<<AIN1D)|(1<<AIN0D)); // disable digital input buffer on AIN0 and AIN1
 	ACSR |= (1<<ACIE); // enable analog comparator interrupt
 
+	/* use timer 1 (with capture unit) to measure PWM */
+	TCCR1A &= ~((1<<WGM11)|(1<<WGM10)); // mode 0: normal (should be per default)
+	TCCR1B &= ~((1<<WGM13)|(1<<WGM12)); // mode 0: normal (should be per default)
+	TCCR1B |= (1<<CS12)|(0<<CS11)|(0<<CS10); // set prescale to 256 for 1.048576s before overflow (PWM should be 3Hz)
+
 	sei(); /* enable interrupts */
 }
 
@@ -128,6 +145,15 @@ int main(void)
 
 	printf(PSTR("welcome to the body scale weight reader\n")); // print welcome message
 	while (true) { // endless loop for micro-controller
+		/* display value if available */
+		if (measurement_flag) {
+			if (pwm_high) {
+				printf("high: %u\n",measurement_value);
+			} else {
+				printf("low: %u\n",measurement_value);
+			}
+			measurement_flag = false;
+		}
 		/* go to sleep and wait for next interrupt */
 		set_sleep_mode(SLEEP_MODE_IDLE);
 		sleep_mode();