diff --git a/src/avr/timer.c b/src/avr/timer.c
index a6da9b4ff..06d8845e7 100644
--- a/src/avr/timer.c
+++ b/src/avr/timer.c
@@ -38,13 +38,6 @@ timer_set(uint16_t next)
     OCR1A = next;
 }
 
-static inline void
-timer_set_clear(uint16_t next)
-{
-    OCR1A = next;
-    TIFR1 = 1<<OCF1A;
-}
-
 static inline void
 timer_repeat_set(uint16_t next)
 {
@@ -78,6 +71,15 @@ timer_init(void)
 }
 DECL_INIT(timer_init);
 
+static void
+timer_shutdown(void)
+{
+    // Reenable timer irq
+    timer_set(timer_get() + 50);
+    TIFR1 = 1<<OCF1A;
+}
+DECL_SHUTDOWN(timer_shutdown);
+
 
 /****************************************************************
  * 32bit timer wrappers
@@ -120,35 +122,15 @@ timer_periodic(void)
     }
 }
 
-#define TIMER_MIN_TICKS 100
-
-// Set the next timer wake time (in absolute clock ticks).  Caller
-// must disable irqs.  The caller should not schedule a time more than
-// a few milliseconds in the future.
-uint8_t
-timer_set_next(uint32_t next)
-{
-    uint32_t cur = timer_read_time();
-    if ((int16_t)(OCR1A - (uint16_t)cur) < 0 && !(TIFR1 & (1<<OCF1A)))
-        // Already processing timer irqs
-        try_shutdown("timer_set_next called during timer dispatch");
-    uint32_t mintime = cur + TIMER_MIN_TICKS;
-    if (sched_is_before(mintime, next)) {
-        timer_set_clear(next);
-        return 0;
-    }
-    timer_set_clear(mintime);
-    return 1;
-}
-
 #define TIMER_IDLE_REPEAT_TICKS 8000
 #define TIMER_REPEAT_TICKS 3000
 
 #define TIMER_MIN_TRY_TICKS 60 // 40 ticks to exit irq; 20 ticks of progress
 #define TIMER_DEFER_REPEAT_TICKS 200
 
-// Similar to timer_set_next(), but wait for the given time if it is
-// in the near future.
+// Set the next timer wake time (in absolute clock ticks) or return 1
+// if the next timer is too close to schedule.  Caller must disable
+// irqs.
 uint8_t
 timer_try_set_next(uint32_t target)
 {
diff --git a/src/generic/misc.h b/src/generic/misc.h
index ce1c8f02e..92d4d1459 100644
--- a/src/generic/misc.h
+++ b/src/generic/misc.h
@@ -12,7 +12,6 @@ void console_push_output(uint8_t len);
 uint32_t timer_from_us(uint32_t us);
 void timer_periodic(void);
 uint32_t timer_read_time(void);
-uint8_t timer_set_next(uint32_t next);
 uint8_t timer_try_set_next(uint32_t next);
 
 size_t alloc_maxsize(size_t reqsize);
diff --git a/src/sam3x8e/timer.c b/src/sam3x8e/timer.c
index bab2512f6..dbc7700e6 100644
--- a/src/sam3x8e/timer.c
+++ b/src/sam3x8e/timer.c
@@ -43,13 +43,6 @@ timer_set(uint32_t value)
     TC0->TC_CHANNEL[0].TC_RA = value;
 }
 
-static void
-timer_set_clear(uint32_t value)
-{
-    TC0->TC_CHANNEL[0].TC_RA = value;
-    TC0->TC_CHANNEL[0].TC_SR; // read to clear irq pending
-}
-
 static void
 timer_init(void)
 {
@@ -69,6 +62,15 @@ timer_init(void)
 }
 DECL_INIT(timer_init);
 
+static void
+timer_shutdown(void)
+{
+    // Reenable timer irq
+    timer_set(timer_read_time() + 50);
+    TC0->TC_CHANNEL[0].TC_SR; // read to clear irq pending
+}
+DECL_SHUTDOWN(timer_shutdown);
+
 // Called by main code once every millisecond.  (IRQs disabled.)
 void
 timer_periodic(void)
@@ -82,28 +84,6 @@ timer_read_time(void)
     return TC0->TC_CHANNEL[0].TC_CV;
 }
 
-#define TIMER_MIN_TICKS 100
-
-// Set the next timer wake time (in absolute clock ticks).  Caller
-// must disable irqs.  The caller should not schedule a time more than
-// a few milliseconds in the future.
-uint8_t
-timer_set_next(uint32_t next)
-{
-    uint32_t cur = timer_read_time();
-    if (sched_is_before(TC0->TC_CHANNEL[0].TC_RA, cur)
-        && !(TC0->TC_CHANNEL[0].TC_SR & TC_SR_CPAS))
-        // Already processing timer irqs
-        try_shutdown("timer_set_next called during timer dispatch");
-    uint32_t mintime = cur + TIMER_MIN_TICKS;
-    if (sched_is_before(mintime, next)) {
-        timer_set_clear(next);
-        return 0;
-    }
-    timer_set_clear(mintime);
-    return 1;
-}
-
 static uint32_t timer_repeat_until;
 #define TIMER_IDLE_REPEAT_TICKS timer_from_us(500)
 #define TIMER_REPEAT_TICKS timer_from_us(100)
@@ -111,8 +91,9 @@ static uint32_t timer_repeat_until;
 #define TIMER_MIN_TRY_TICKS timer_from_us(1)
 #define TIMER_DEFER_REPEAT_TICKS timer_from_us(5)
 
-// Similar to timer_set_next(), but wait for the given time if it is
-// in the near future.
+// Set the next timer wake time (in absolute clock ticks) or return 1
+// if the next timer is too close to schedule.  Caller must disable
+// irqs.
 uint8_t
 timer_try_set_next(uint32_t next)
 {
diff --git a/src/sched.c b/src/sched.c
index 19e428be6..7e4a86a1c 100644
--- a/src/sched.c
+++ b/src/sched.c
@@ -101,33 +101,39 @@ sched_timer(struct timer *add)
 {
     uint32_t waketime = add->waketime;
     irqstatus_t flag = irq_save();
-    if (sched_is_before(waketime, timer_list->waketime)) {
-        // This timer is the next - insert at front of list and reschedule
-        add->next = timer_list;
-        timer_list = add;
-        uint8_t ret = timer_set_next(waketime);
-        if (ret)
-            shutdown("Timer too close");
-    } else {
-        // Find position in list and insert
-        struct timer *pos = timer_list;
-        while (!sched_is_before(waketime, pos->next->waketime))
-            pos = pos->next;
-        add->next = pos->next;
-        pos->next = add;
-    }
+    if (sched_is_before(waketime, timer_list->waketime))
+        // Timer in past (or very near future)
+        shutdown("Timer too close");
+    // Find position in list and insert
+    struct timer *pos = timer_list;
+    while (!sched_is_before(waketime, pos->next->waketime))
+        pos = pos->next;
+    add->next = pos->next;
+    pos->next = add;
     irq_restore(flag);
 }
 
+// The deleted timer is used when deleting an active timer.
+static uint_fast8_t
+deleted_event(struct timer *t)
+{
+    return SF_DONE;
+}
+
+static struct timer deleted_timer = {
+    .func = deleted_event,
+};
+
 // Remove a timer that may be live.
 void
 sched_del_timer(struct timer *del)
 {
     irqstatus_t flag = irq_save();
     if (timer_list == del) {
-        // Deleting the next active timer - delete and reschedule
-        timer_list = del->next;
-        timer_set_next(timer_list->waketime);
+        // Deleting the next active timer - replace with deleted_timer
+        deleted_timer.waketime = del->waketime;
+        deleted_timer.next = del->next;
+        timer_list = &deleted_timer;
     } else {
         // Find and remove from timer list (if present)
         struct timer *pos;
@@ -197,13 +203,14 @@ sched_timer_kick(void)
 
 // Shutdown all user timers on an emergency stop.
 static void
-timer_shutdown(void)
+sched_timer_shutdown(void)
 {
-    timer_list = &ms_timer;
+    timer_list = &deleted_timer;
+    deleted_timer.waketime = ms_timer.waketime;
+    deleted_timer.next = &ms_timer;
     ms_timer.next = &sentinel_timer;
-    timer_set_next(timer_list->waketime);
 }
-DECL_SHUTDOWN(timer_shutdown);
+DECL_SHUTDOWN(sched_timer_shutdown);
 
 
 /****************************************************************
diff --git a/src/simulator/main.c b/src/simulator/main.c
index 1bffc265c..f45b5c459 100644
--- a/src/simulator/main.c
+++ b/src/simulator/main.c
@@ -69,12 +69,6 @@ timer_read_time(void)
     return 0; // XXX
 }
 
-uint8_t
-timer_set_next(uint32_t next)
-{
-    return 0;
-}
-
 uint8_t
 timer_try_set_next(uint32_t next)
 {