--- /dev/null
+/*
+ * Copyright © 2012 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>
+#include <ao_exti.h>
+
+static void (*pcint_callback)(void);
+static uint8_t pcint_mask;
+
+ISR(PCINT0_vect)
+{
+ if (PINB & pcint_mask)
+ (*pcint_callback)();
+}
+
+void
+ao_exti_setup_port(uint8_t pin, uint8_t mode, void (*callback)(void))
+{
+ pcint_callback = callback;
+ pcint_mask = (1 << pin);
+ ao_exti_disable(PORTB, pin);
+ GIMSK |= (1 << PCIE);
+}