From bdfc4c5507af5127b6807e204ce45f776aae9829 Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Mon, 4 Oct 2010 13:58:00 +0200
Subject: [PATCH] clock.c: Add a comment about interrupt priorities.

---
 clock.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/clock.c b/clock.c
index ecfa572..9056814 100644
--- a/clock.c
+++ b/clock.c
@@ -27,6 +27,13 @@ void clock_setup() {
 
 	// no compare match, CTC mode
 	TCCR2A = MASK(WGM21);
+	// TODO: Timer 2 has higher priority than Timer 1 used for the stepper
+	//       interrupts, which is bad. See AVR Reference Manual p. 9:
+	//          "The interrupts have priority in accordance
+	//           with their Interrupt Vector position. The
+	//           lower the Interrupt Vector address, the higher
+	//           the priority."
+	//       in conjunction with p. 63 (interrupt vector table).
 
 	// 128 prescaler (16MHz / 128 = 125KHz)
 	TCCR2B = MASK(CS22) | MASK(CS20);