From adc673c160ccdab692adbb59b9ddbf10bae8b206 Mon Sep 17 00:00:00 2001
From: Michael Gernoth <michael@gernoth.net>
Date: Mon, 23 Aug 2010 19:44:34 +0200
Subject: [PATCH] use tristate on outputs. Tested with a PC connected and
 everything works :-)

---
 bmc/chassis.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/bmc/chassis.c b/bmc/chassis.c
index 2259d86..29541f2 100644
--- a/bmc/chassis.c
+++ b/bmc/chassis.c
@@ -31,7 +31,6 @@ static void chassis_set_pins(uint8_t pins, uint8_t state);
 void chassis_init()
 {
 	chassis_set_pins((1<<POWER_PIN) | (1<<RESET_PIN), 0);
-	CDDR |= ((1<<POWER_PIN) | (1<<RESET_PIN));
 
 	/* About 1ms */
 	OCR0 = ((F_CPU/64)/1000) - 1;
@@ -41,16 +40,27 @@ void chassis_init()
 
 }
 
+/* gracefully transition between tri-state and active */
 static void chassis_set_pins(uint8_t pins, uint8_t state)
 {
-#ifdef ACTIVE_LOW
-	state = !state;
-#endif
-
 	if(state) {
+		/* active */
+#ifndef ACTIVE_LOW
+		/* Pull UPs for a short moment... */
 		CPORT |= pins;
+#endif
+		CDDR |= pins;
+#ifdef ACTIVE_LOW
+		CPORT &= ~pins;
+#endif
 	} else {
+#ifdef ACTIVE_LOW
+		CPORT &= ~pins; /* NoOp... */
+#endif
+		CDDR &= ~pins;
+#ifndef ACTIVE_LOW
 		CPORT &= ~pins;
+#endif
 	}
 }
 
-- 
2.39.2