--- /dev/null
+/*
+ * Copyright © 2011 Keith Packard <keithp@keithp.com>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#include "ao.h"
+
+/*
+ * AltOS always cranks the clock to the max frequency
+ */
+
+void
+ao_clock_init(void)
+{
+ /* disable RC clock */
+ CLKSEL0 &= ~(1 << RCE);
+
+ /* Disable PLL */
+ PLLCSR &= ~(1 << PLLE);
+
+ /* Enable external clock */
+ CLKSEL0 |= (1 << EXTE);
+
+ /* wait for external clock to be ready */
+ while ((CLKSTA & (1 << EXTON)) == 0)
+ ;
+
+ /* select external clock */
+ CLKSEL0 |= (1 << CLKS);
+
+ /* Disable the clock prescaler */
+ cli();
+ CLKPR = (1 << CLKPCE);
+
+ /* Always run the system clock at 8MHz */
+#if AVR_CLOCK > 12000000UL
+ CLKPR = 1;
+#else
+ CLKPR = 0;
+#endif
+ sei();
+
+ /* Set up the PLL to use the crystal */
+
+ /* Use primary system clock as PLL source */
+ PLLFRQ = ((0 << PINMUX) | /* Use primary clock */
+ (0 << PLLUSB) | /* No divide by 2 for USB */
+ (0 << PLLTM0) | /* Disable high speed timer */
+ (0x4 << PDIV0)); /* 48MHz PLL clock */
+
+ /* Set the frequency of the crystal */
+#if AVR_CLOCK > 12000000UL
+ PLLCSR |= (1 << PINDIV); /* For 16MHz crystal on Teensy board */
+#else
+ PLLCSR &= ~(1 << PINDIV); /* For 8MHz crystal on TeleScience board */
+#endif
+
+ /* Enable the PLL */
+ PLLCSR |= (1 << PLLE);
+ while (!(PLLCSR & (1 << PLOCK)))
+ ;
+
+ set_sleep_mode(SLEEP_MODE_IDLE);
+ sleep_enable();
+}