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+#ifndef utils_h
+#define utils_h
+// utils.h
+// n.avr.utils - AVR utilities module. {{{
+//
+// Copyright (C) 2004 Nicolas Schodet
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+//
+// Contact :
+// Web: http://perso.efrei.fr/~schodet/
+// Email: <contact@ni.fr.eu.org>
+// }}}
+#include "avrconfig.h"
+
+#include <avr/delay.h>
+#include <inttypes.h>
+
+/** Delay in ns. Do not call this macro with a variable parameter. If you
+ * want a variable delay, prefer looping over a fixed delay.
+ *
+ * Maximum delay is about 3.3s at 20MHz.
+ *
+ * Should be a inline function, but GCC do not inline like I want.
+ */
+#define delay_ns(ns_) \
+do { \
+ static const uint32_t ns = (ns_); \
+ static const uint32_t t = 1000000000lu / AC_FREQ; \
+ static const uint32_t t8 = t * 255 * 3; \
+ static const uint32_t t16 = t * 65535 * 4; \
+ if (ns <= t) \
+ { \
+ /* Delay shorter than 1 instruction. */ \
+ asm volatile ("nop" : :); \
+ } \
+ else if (ns <= t * 2) \
+ { \
+ /* Delay shorter than 2 instruction. */ \
+ asm volatile ("nop\n\tnop" : :); \
+ } \
+ else if (ns <= t * 3) \
+ { \
+ /* Delay shorter than 3 instruction. */ \
+ asm volatile ("nop\n\tnop\n\tnop" : :); \
+ } \
+ else if (ns <= t8) \
+ { \
+ static const uint8_t b = (uint8_t) ((ns + t * 3 - 1) / (t * 3)); \
+ _delay_loop_1 (b); \
+ } \
+ else if (ns <= t16) \
+ { \
+ static const uint16_t b = (uint16_t) ((ns + t * 4 - 1) / (t * 4)); \
+ _delay_loop_2 (b); \
+ } \
+ else \
+ { \
+ static const uint8_t ob = (uint8_t) ((ns + t16 - 1) / t16); \
+ static const uint16_t ib = (uint16_t) ((ns / ob + t * 4 - 1) \
+ / (t * 4)); \
+ uint8_t i; \
+ i = ob; \
+ while (i--) \
+ _delay_loop_2 (ib); \
+ } \
+} while (0)
+
+/** Shortcut for delay_ns (us * 1000). */
+#define delay_us(us) delay_ns ((us) * 1000)
+
+/** Shortcut for delay_ns (ms * 1000 * 1000). */
+#define delay_ms(ms) delay_ns ((ms) * 1000 * 1000)
+
+/** Delay in seconds. Maximum of 256 seconds. */
+extern inline void
+delay_s (uint8_t s)
+{
+ while (s--)
+ delay_ns (1000000000);
+}
+
+#endif // utils_h