--- /dev/null
+/*
+ * Copyright © 2012 Robert D. Garbee <robert@gag.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_pwmin.h"
+
+/*
+ * This code implements a PWM input using ICP3.
+ *
+ * The initial use is to measure wind speed in the ULA/Ball summer intern
+ * project payload developed at Challenger Middle School.
+ */
+
+volatile __data uint16_t ao_icp3_count;
+
+static void
+ao_pwmin_display(void) __reentrant
+{
+ /* display the most recent value */
+ printf("icp 3: %5u\n", ao_icp3_count);
+
+}
+ISR(TIMER3_CAPT_vect)
+{
+ uint8_t lo = ICR3L;
+ uint8_t hi = ICR3H;
+ ao_icp3_count = (hi <<8) | lo;
+}
+
+__code struct ao_cmds ao_pwmin_cmds[] = {
+ { ao_pwmin_display, "p\0PWM input" },
+ { 0, NULL },
+};
+
+void
+ao_pwmin_init(void)
+{
+ /* do hardware setup here */
+ TCCR3A = ((0 << WGM31) | /* normal mode, OCR3A */
+ (0 << WGM30)); /* normal mode, OCR3A */
+ TCCR3B = ((1 << ICNC3) | /* input capture noise canceler on */
+ (0 << ICES3) | /* input capture on falling edge (don't care) */
+ (0 << WGM33) | /* normal mode, OCR3A */
+ (0 << WGM32) | /* normal mode, OCR3A */
+ (4 << CS30)); /* clk/256 from prescaler */
+
+
+
+ TIMSK3 = (1 << ICIE3); /* Interrupt on input compare */
+
+ /* set the spike filter bit in the TCCR3B register */
+
+ ao_cmd_register(&ao_pwmin_cmds[0]);
+}
+
+
--- /dev/null
+/*
+ * Copyright © 2012 Robert D. Garbee <robert@gag.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.
+ */
+
+void ao_pwmin_init(void);