From ce17fa131cbcca5b27995c718acb5b7c2b3c5e7c Mon Sep 17 00:00:00 2001
From: George Oikonomou <g.oikonomou@bristol.ac.uk>
Date: Mon, 2 Apr 2012 16:49:07 +0100
Subject: [PATCH] Stack-friendly cc243x clock ISR enabled by default

This new approach (CLOCK_CONF_ACCURATE=0) was not as inaccurate
as originally thought. In fact, it has pretty much the same
accuracy as the old, stack-hungry version.

* Renamed the define from CLOCK_CONF_ACCURATE (1: old) to
  CLOCK_CONF_STACK_FRIENDLY (1: new) to stop implying
  that one is more accurate than the other.
* Using CLOCK_CONF_STACK_FRIENDLY by default.
---
 cpu/cc2430/dev/clock.c                      | 17 +++++++----------
 platform/sensinode/contiki-conf.h           | 10 ++++++----
 platform/sensinode/contiki-sensinode-main.c | 10 +++-------
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/cpu/cc2430/dev/clock.c b/cpu/cc2430/dev/clock.c
index fa902c0e3..b81bb4985 100644
--- a/cpu/cc2430/dev/clock.c
+++ b/cpu/cc2430/dev/clock.c
@@ -47,15 +47,12 @@
 
 /* Used in sleep timer interrupt for calculating the next interrupt time */
 static unsigned long timer_value;
-/*starts calculating the ticks right after reset*/
-#if CLOCK_CONF_ACCURATE
-static volatile __data clock_time_t count = 0;
-#else
-volatile __data clock_time_t count = 0;
-/* accurate clock is stack hungry */
+#if CLOCK_CONF_STACK_FRIENDLY
 volatile __bit sleep_flag;
+#else
 #endif
-/*calculates seconds*/
+
+static volatile __data clock_time_t count = 0; /* Uptime in ticks */
 static volatile __data clock_time_t seconds = 0; /* Uptime in secs */
 /*---------------------------------------------------------------------------*/
 /**
@@ -152,13 +149,13 @@ clock_ISR(void) __interrupt(ST_VECTOR)
     ++seconds;
   }
   
-#if CLOCK_CONF_ACCURATE
+#if CLOCK_CONF_STACK_FRIENDLY
+  sleep_flag = 1;
+#else
   if(etimer_pending()
       && (etimer_next_expiration_time() - count - 1) > MAX_TICKS) {
     etimer_request_poll();
   }
-#else
-  sleep_flag = 1;
 #endif
   
   IRCON_STIF = 0;
diff --git a/platform/sensinode/contiki-conf.h b/platform/sensinode/contiki-conf.h
index 278ba74de..2c5494cee 100644
--- a/platform/sensinode/contiki-conf.h
+++ b/platform/sensinode/contiki-conf.h
@@ -10,10 +10,12 @@
 #include "project-conf.h"
 #endif /* PROJECT_CONF_H */
 
-/* The clock ISR is stack-hungry and may cause crashes.
- * Define this as 0 if you are suffering from frequent stack overflows */
-#ifndef CLOCK_CONF_ACCURATE
-#define CLOCK_CONF_ACCURATE 1
+/*
+ * Define this as 1 to poll the etimer process from within main instead of from
+ * the clock ISR. This reduces the ISR's stack usage and may prevent crashes.
+ */
+#ifndef CLOCK_CONF_STACK_FRIENDLY
+#define CLOCK_CONF_STACK_FRIENDLY 1
 #endif
 
 /* Memory filesystem RAM size. */
diff --git a/platform/sensinode/contiki-sensinode-main.c b/platform/sensinode/contiki-sensinode-main.c
index 66d2d0e75..24862336a 100644
--- a/platform/sensinode/contiki-sensinode-main.c
+++ b/platform/sensinode/contiki-sensinode-main.c
@@ -54,10 +54,7 @@ static __data int len;
 #define PUTCHAR(...) do {} while(0)
 #endif
 
-
-#if !CLOCK_CONF_ACCURATE
-extern volatile __data clock_time_t count;
-/* accurate clock is stack hungry */
+#if CLOCK_CONF_STACK_FRIENDLY
 extern volatile __bit sleep_flag;
 #endif
 
@@ -294,11 +291,10 @@ main(void)
       /* Reset watchdog and handle polls and events */
       watchdog_periodic();
 
-      /**/
-#if !CLOCK_CONF_ACCURATE
+#if CLOCK_CONF_STACK_FRIENDLY
       if(sleep_flag) {
         if(etimer_pending() &&
-            (etimer_next_expiration_time() - count - 1) > MAX_TICKS) { /*core/sys/etimer.c*/
+            (etimer_next_expiration_time() - clock_time() - 1) > MAX_TICKS) {
           etimer_request_poll();
         }
         sleep_flag = 0;