--- /dev/null
+/*
+ * Copyright © 2020 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, 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.,
+ * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef _AO_DAC_SAMD21_H_
+#define _AO_DAC_SAMD21_H_
+
+void
+ao_dac_set(uint16_t value);
+
+#ifdef SNEK_SAMD21_DAC_TIMER
+void
+ao_dac_set_hz(float hz);
+#endif
+
+void
+ao_dac_init(void);
+
+#endif /* _AO_DAC_SAMD21_H_ */