From 70451090900fd1079e1ab701495556b331461da6 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@almesberger.net>
Date: Thu, 21 Jun 2012 08:55:43 -0300
Subject: [PATCH] fw/accel.c: keep track of uptime and return it with uptime()
 (untested)

---
 fw/sweep.c | 26 ++++++++++++++++++++++++--
 fw/sweep.h |  2 +-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/fw/sweep.c b/fw/sweep.c
index 603c0d7..059c286 100644
--- a/fw/sweep.c
+++ b/fw/sweep.c
@@ -24,6 +24,7 @@
 volatile bool sweeping = 0;
 
 
+static volatile uint32_t t_up;	/* uptime, in timer ticks (wraps in 4295 s) */
 static volatile uint32_t t_sw;	/* cumulative number of timer ticks in sweep */
 
 static uint16_t wait_periods;	/* number of periods to wait before image */
@@ -38,9 +39,13 @@ static bool forward;
 
 ISR(TIMER1_OVF_vect)
 {
-	/* update the sweep time */
+	uint16_t t;
 
-	t_sw += ICR1;
+	/* update the time counters */
+
+	t = ICR1;
+	t_sw += t;
+	t_up += t;
 
 	/* if at the end of the image, only update the time */
 
@@ -79,6 +84,23 @@ ISR(TIMER1_OVF_vect)
 }
 
 
+uint32_t uptime(void)
+{
+	uint32_t a, b;
+	uint16_t d;
+
+	do {
+		cli();
+		a = t_up;
+		d = ICR1;
+		b = t_up;
+		sei();
+	}
+	while (a != b);
+	return a+d;
+}
+
+
 void sweep_image(const struct sweep *sweep)
 {
 	TCCR1B = 0;	/* stop the timer */
diff --git a/fw/sweep.h b/fw/sweep.h
index dbd914a..08b325e 100644
--- a/fw/sweep.h
+++ b/fw/sweep.h
@@ -29,7 +29,7 @@ struct sweep {
 
 extern volatile bool sweeping;
 
-
+uint32_t uptime(void);
 void sweep_image(const struct sweep *sweep);
 void sweep_init(void);