From 3ee9710f359d5cdac69a24b29087aa23ddfc2667 Mon Sep 17 00:00:00 2001
From: Chuck McManis <cmcmanis@mcmanis.com>
Date: Sun, 12 Apr 2020 21:25:08 -0700
Subject: [PATCH] STM32F4: I2C Noise Filter Register

---
 include/libopencm3/stm32/f4/i2c.h | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/libopencm3/stm32/f4/i2c.h b/include/libopencm3/stm32/f4/i2c.h
index e2a65e16..a6b8de28 100644
--- a/include/libopencm3/stm32/f4/i2c.h
+++ b/include/libopencm3/stm32/f4/i2c.h
@@ -31,9 +31,33 @@ LGPL License Terms @ref lgpl_license
 #ifndef LIBOPENCM3_I2C_H
 #define LIBOPENCM3_I2C_H
 
+#include <libopencm3/stm32/memorymap.h>
 #include <libopencm3/stm32/common/i2c_common_v1.h>
 
-/**@{*/
+/**
+@addtogroup i2c_defines
+@{*/
+
+/** FLTR register (I2Cx_FLTR) (noise filter) */
+#define I2C_FLTR(i2c_base)		MMIO32((i2c_base) + 0x24)
+#define I2C1_FLTR			I2C_FLTR(I2C1)
+#define I2C2_FLTR			I2C_FLTR(I2C2)
+#define I2C3_FLTR			I2C_FLTR(I2C3)
+
+/**
+ * Bits [3:0] DNF - Digital noise filter
+ * These bits configure a digital noise filter on SDA and SCL pins.
+ * Value sets minimum pulse width needed to trigger i2c operations.
+ * 0 disables, 1 - 15 set minimum width to 'n' * TPCLK1
+ */
+#define I2C_FLTR_DNF_MASK	0xF
+#define I2C_FLTR_DNF_SHIFT	0
+
+/**
+ * Bit 4 - Analog Noise filter disable
+ * Turns off the built in analog noise filter.
+ */
+#define I2C_FLTR_ANOFF		(1<<4)
 
 /**@}*/