diff --git a/firmware/common/si5351c.h b/firmware/common/si5351c.h
new file mode 100644
index 00000000..e847852c
--- /dev/null
+++ b/firmware/common/si5351c.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2012 Michael Ossmann
+ * Copyright 2012 Jared Boone
+ *
+ * This file is part of HackRF.
+ *
+ * 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, 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; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __SI5351C_H
+#define __SI5351C_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include <stdint.h>
+
+#define SI5351C_I2C_ADDR (0x60 << 1)
+
+void si5351c_disable_all_outputs();
+void si5351c_disable_oeb_pin_control();
+void si5351c_power_down_all_clocks();
+void si5351c_set_crystal_configuration();
+void si5351c_enable_xo_and_ms_fanout();
+void si5351c_configure_pll_sources_for_xtal();
+void si5351c_configure_pll1_multisynth();
+void si5351c_configure_multisynth( const uint_fast8_t ms_number,
+    	const uint32_t p1, const uint32_t p2, const uint32_t p3);
+void si5351c_configure_clock_control();
+void si5351c_enable_clock_outputs();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __SI5351C_H */