From 34845a62b092fada2e04ea91f6e4cd0a027d491b Mon Sep 17 00:00:00 2001
From: Julian Oes <julian@oes.ch>
Date: Mon, 19 Jan 2026 06:09:29 +1300
Subject: [PATCH] AirBrainH743: add external I2C

This is for future/later board revisions.
---
 boards/gearup/airbrainh743/nuttx-config/include/board.h | 7 +++++++
 boards/gearup/airbrainh743/nuttx-config/nsh/defconfig   | 1 +
 boards/gearup/airbrainh743/src/i2c.cpp                  | 2 ++
 3 files changed, 10 insertions(+)

diff --git a/boards/gearup/airbrainh743/nuttx-config/include/board.h b/boards/gearup/airbrainh743/nuttx-config/include/board.h
index 9898c25305..56aafd3eaa 100644
--- a/boards/gearup/airbrainh743/nuttx-config/include/board.h
+++ b/boards/gearup/airbrainh743/nuttx-config/include/board.h
@@ -319,6 +319,7 @@
 /* I2C
  *
  * I2C1: Internal (PB6 SCL, PB7 SDA)
+ * I2C4: External (PD12 SCL, PD13 SDA)
  */
 
 #define GPIO_I2C1_SCL GPIO_I2C1_SCL_1       /* PB6  */
@@ -327,6 +328,12 @@
 #define GPIO_I2C1_SCL_GPIO                  (GPIO_OUTPUT | GPIO_OPENDRAIN | GPIO_SPEED_50MHz | GPIO_OUTPUT_SET | GPIO_PORTB | GPIO_PIN6)
 #define GPIO_I2C1_SDA_GPIO                  (GPIO_OUTPUT | GPIO_OPENDRAIN | GPIO_SPEED_50MHz | GPIO_OUTPUT_SET | GPIO_PORTB | GPIO_PIN7)
 
+#define GPIO_I2C4_SCL GPIO_I2C4_SCL_1       /* PD12 */
+#define GPIO_I2C4_SDA GPIO_I2C4_SDA_1       /* PD13 */
+
+#define GPIO_I2C4_SCL_GPIO                  (GPIO_OUTPUT | GPIO_OPENDRAIN | GPIO_SPEED_50MHz | GPIO_OUTPUT_SET | GPIO_PORTD | GPIO_PIN12)
+#define GPIO_I2C4_SDA_GPIO                  (GPIO_OUTPUT | GPIO_OPENDRAIN | GPIO_SPEED_50MHz | GPIO_OUTPUT_SET | GPIO_PORTD | GPIO_PIN13)
+
 
 /* USB
  *
diff --git a/boards/gearup/airbrainh743/nuttx-config/nsh/defconfig b/boards/gearup/airbrainh743/nuttx-config/nsh/defconfig
index 56f41becc6..a31ca060ed 100644
--- a/boards/gearup/airbrainh743/nuttx-config/nsh/defconfig
+++ b/boards/gearup/airbrainh743/nuttx-config/nsh/defconfig
@@ -190,6 +190,7 @@ CONFIG_STM32H7_DMACAPABLE=y
 CONFIG_STM32H7_DMAMUX1=y
 CONFIG_STM32H7_FLOWCONTROL_BROKEN=y
 CONFIG_STM32H7_I2C1=y
+CONFIG_STM32H7_I2C4=y
 CONFIG_STM32H7_I2C_DYNTIMEO=y
 CONFIG_STM32H7_I2C_DYNTIMEO_STARTSTOP=10
 CONFIG_STM32H7_OTGFS=y
diff --git a/boards/gearup/airbrainh743/src/i2c.cpp b/boards/gearup/airbrainh743/src/i2c.cpp
index 9bb4992776..26e33dc7fe 100644
--- a/boards/gearup/airbrainh743/src/i2c.cpp
+++ b/boards/gearup/airbrainh743/src/i2c.cpp
@@ -38,8 +38,10 @@
  *
  * I2C1: Internal bus - PB6 (SCL), PB7 (SDA)
  *       Devices: DPS310 baro @ 0x76, LIS2MDL compass @ 0x1E
+ * I2C4: External bus - PD12 (SCL), PD13 (SDA)
  */
 
 constexpr px4_i2c_bus_t px4_i2c_buses[I2C_BUS_MAX_BUS_ITEMS] = {
 	initI2CBusInternal(1),
+	initI2CBusExternal(4),
 };