diff --git a/firmware/ice40-riscv/icE1usb/misc.h b/firmware/ice40-riscv/icE1usb/misc.h
new file mode 100644
index 0000000..36126da
--- /dev/null
+++ b/firmware/ice40-riscv/icE1usb/misc.h
@@ -0,0 +1,23 @@
+/*
+ * misc.h
+ *
+ * Copyright (C) 2019-2020  Sylvain Munaut <tnt@246tNt.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+enum pdm_chan {
+	PDM_CLK_LO	= 0,
+	PDM_CLK_HI	= 1,
+	PDM_E1_N	= 2,
+	PDM_E1_P	= 3,
+	PDM_E1_CT	= 4,
+};
+
+void pdm_set(int chan, bool enable, unsigned value, bool normalize);
+
+uint16_t e1_tick_read(void);