--- /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.
+ */
+
+#ifndef _AO_HMC5883_H_
+#define _AO_HMC5883_H_
+
+#define HMC5883_ADDR_WRITE 0x3c
+#define HMC5883_ADDR_READ 0x3d
+
+#define HMC5883_CONFIG_A 0
+#define HMC5883_CONFIG_B 1
+#define HMC5883_MODE 2
+#define HMC5883_X_MSB 3
+#define HMC5883_X_LSB 4
+#define HMC5883_Y_MSB 5
+#define HMC5883_Y_LSB 6
+#define HMC5883_Z_MSB 7
+#define HMC5883_Z_LSB 8
+#define HMC5883_STATUS 9
+#define HMC5883_ID_A 10
+#define HMC5883_ID_B 11
+#define HMC5883_ID_C 12
+
+void
+ao_hmc5883_init(void);
+
+#endif /* _AO_HMC5883_H_ */