diff --git a/wave/wave.h b/wave/wave.h
new file mode 100644
index 0000000..50fe93b
--- /dev/null
+++ b/wave/wave.h
@@ -0,0 +1,20 @@
+#pragma once
+
+struct pdmout {
+  volatile uint16_t amplitude;
+  volatile uint16_t flags;
+};
+
+#define PDMOUT_FLAG_ENABLE_pos 0
+#define PDMOUT_FLAG_ENABLE_msk (1 << PDMOUT_FLAG_ENABLE_pos)
+
+struct square {
+  volatile uint16_t period;
+  volatile uint16_t high_val;
+  volatile uint16_t low_val;
+  volatile uint16_t output_address;
+  volatile uint16_t flags;
+};
+
+#define SQUARE_FLAG_ENABLE_pos 0
+#define SQUARE_FLAG_ENABLE_msk (1 << SQUARE_FLAG_ENABLE_pos)