diff --git a/targets/stm32f207zg-nucleo/BUILD.gn b/targets/stm32f207zg-nucleo/BUILD.gn
index 2c908db..170b0f4 100644
--- a/targets/stm32f207zg-nucleo/BUILD.gn
+++ b/targets/stm32f207zg-nucleo/BUILD.gn
@@ -24,6 +24,18 @@
   toolchains = pw_target_toolchain_stm32f207zg_nucleo_list
 }
 
+config("module_config_options") {
+  cflags = [
+    "-include",
+    rebase_path("module_config_overrides.h", root_build_dir),
+  ]
+}
+
+pw_source_set("module_config_overrides") {
+  public_configs = [ ":module_config_options" ]
+  sources = [ "module_config_overrides.h" ]
+}
+
 if (current_toolchain != default_toolchain) {
   pw_source_set("pre_init") {
     public_deps = [ "$dir_pw_sys_io_stm32cube" ]
diff --git a/targets/stm32f207zg-nucleo/module_config_overrides.h b/targets/stm32f207zg-nucleo/module_config_overrides.h
new file mode 100644
index 0000000..b73e0d6
--- /dev/null
+++ b/targets/stm32f207zg-nucleo/module_config_overrides.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// Configure the UART for pw_sys_io_stm32cube.
+#define PW_SYS_IO_STM32CUBE_USART_NUM 3
+#define PW_SYS_IO_STM32CUBE_GPIO_PORT D
+#define PW_SYS_IO_STM32CUBE_GPIO_TX_PIN 8
+#define PW_SYS_IO_STM32CUBE_GPIO_RX_PIN 9
diff --git a/targets/stm32f207zg-nucleo/target_toolchains.gni b/targets/stm32f207zg-nucleo/target_toolchains.gni
index 5f57d74..9c6bd8d 100644
--- a/targets/stm32f207zg-nucleo/target_toolchains.gni
+++ b/targets/stm32f207zg-nucleo/target_toolchains.gni
@@ -59,10 +59,8 @@
       "$dir_pw_sync_baremetal:interrupt_spin_lock"
   pw_log_BACKEND = dir_pw_log_basic
   pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube
-  pw_sys_io_stm32cube_usart_num = "3"
-  pw_sys_io_stm32cube_gpio_port = "D"
-  pw_sys_io_stm32cube_gpio_tx_pin = "8"
-  pw_sys_io_stm32cube_gpio_rx_pin = "9"
+  pw_sys_io_stm32cube_CONFIG =
+      "//targets/stm32f207zg-nucleo:module_config_overrides"
 
   #TODO: remove dependency on stm32f429i-disc1 rpc server.
   pw_rpc_system_server_BACKEND =
diff --git a/targets/stm32f429i_disc1_stm32cube/BUILD.gn b/targets/stm32f429i_disc1_stm32cube/BUILD.gn
index 2e3c575..fd0495a 100644
--- a/targets/stm32f429i_disc1_stm32cube/BUILD.gn
+++ b/targets/stm32f429i_disc1_stm32cube/BUILD.gn
@@ -24,6 +24,18 @@
   toolchains = pw_target_toolchain_stm32f429i_disc1_list
 }
 
+config("module_config_options") {
+  cflags = [
+    "-include",
+    rebase_path("module_config_overrides.h", root_build_dir),
+  ]
+}
+
+pw_source_set("module_config_overrides") {
+  public_configs = [ ":module_config_options" ]
+  sources = [ "module_config_overrides.h" ]
+}
+
 config("pw_malloc_active") {
   if (pw_malloc_BACKEND != "") {
     defines = [ "PW_MALLOC_ACTIVE=1" ]
diff --git a/targets/stm32f429i_disc1_stm32cube/module_config_overrides.h b/targets/stm32f429i_disc1_stm32cube/module_config_overrides.h
new file mode 100644
index 0000000..5451e2c
--- /dev/null
+++ b/targets/stm32f429i_disc1_stm32cube/module_config_overrides.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// Configure the UART for pw_sys_io_stm32cube.
+#define PW_SYS_IO_STM32CUBE_USART_NUM 1
+#define PW_SYS_IO_STM32CUBE_GPIO_PORT A
+#define PW_SYS_IO_STM32CUBE_GPIO_TX_PIN 9
+#define PW_SYS_IO_STM32CUBE_GPIO_RX_PIN 10
diff --git a/targets/stm32f429i_disc1_stm32cube/target_toolchains.gni b/targets/stm32f429i_disc1_stm32cube/target_toolchains.gni
index 85ac957..f8c9e61 100644
--- a/targets/stm32f429i_disc1_stm32cube/target_toolchains.gni
+++ b/targets/stm32f429i_disc1_stm32cube/target_toolchains.gni
@@ -53,10 +53,8 @@
       "$dir_pw_sync_baremetal:interrupt_spin_lock"
   pw_log_BACKEND = dir_pw_log_basic
   pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube
-  pw_sys_io_stm32cube_usart_num = "1"
-  pw_sys_io_stm32cube_gpio_port = "A"
-  pw_sys_io_stm32cube_gpio_tx_pin = "9"
-  pw_sys_io_stm32cube_gpio_rx_pin = "10"
+  pw_sys_io_stm32cube_CONFIG =
+      "//targets/stm32f429i_disc1_stm32cube:module_config_overrides"
 
   #TODO: remove dependency on stm32f429i-disc1 rpc server.
   pw_rpc_system_server_BACKEND =
diff --git a/targets/stm32f439zi_nucleo/BUILD.gn b/targets/stm32f439zi_nucleo/BUILD.gn
index 374039d..4996547 100644
--- a/targets/stm32f439zi_nucleo/BUILD.gn
+++ b/targets/stm32f439zi_nucleo/BUILD.gn
@@ -25,6 +25,18 @@
   toolchains = pw_target_toolchain_stm32f439zi_nucleo_list
 }
 
+config("module_config_options") {
+  cflags = [
+    "-include",
+    rebase_path("module_config_overrides.h", root_build_dir),
+  ]
+}
+
+pw_source_set("module_config_overrides") {
+  public_configs = [ ":module_config_options" ]
+  sources = [ "module_config_overrides.h" ]
+}
+
 config("pw_malloc_active") {
   if (pw_malloc_BACKEND != "") {
     defines = [ "PW_MALLOC_ACTIVE=1" ]
diff --git a/targets/stm32f439zi_nucleo/module_config_overrides.h b/targets/stm32f439zi_nucleo/module_config_overrides.h
new file mode 100644
index 0000000..b73e0d6
--- /dev/null
+++ b/targets/stm32f439zi_nucleo/module_config_overrides.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// Configure the UART for pw_sys_io_stm32cube.
+#define PW_SYS_IO_STM32CUBE_USART_NUM 3
+#define PW_SYS_IO_STM32CUBE_GPIO_PORT D
+#define PW_SYS_IO_STM32CUBE_GPIO_TX_PIN 8
+#define PW_SYS_IO_STM32CUBE_GPIO_RX_PIN 9
diff --git a/targets/stm32f439zi_nucleo/target_toolchains.gni b/targets/stm32f439zi_nucleo/target_toolchains.gni
index d235ad0..7770896 100644
--- a/targets/stm32f439zi_nucleo/target_toolchains.gni
+++ b/targets/stm32f439zi_nucleo/target_toolchains.gni
@@ -58,10 +58,8 @@
       "$dir_pw_sync_baremetal:interrupt_spin_lock"
   pw_log_BACKEND = dir_pw_log_basic
   pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube
-  pw_sys_io_stm32cube_usart_num = "3"
-  pw_sys_io_stm32cube_gpio_port = "D"
-  pw_sys_io_stm32cube_gpio_tx_pin = "8"
-  pw_sys_io_stm32cube_gpio_rx_pin = "9"
+  pw_sys_io_stm32cube_CONFIG =
+      "//targets/stm32f439zi_nucleo:module_config_overrides"
 
   #TODO: remove dependency on stm32f429i-disc1 rpc server.
   pw_rpc_system_server_BACKEND =
diff --git a/targets/stm32h753zi-nucleo/BUILD.gn b/targets/stm32h753zi-nucleo/BUILD.gn
index ce47909..a6df66d 100644
--- a/targets/stm32h753zi-nucleo/BUILD.gn
+++ b/targets/stm32h753zi-nucleo/BUILD.gn
@@ -24,6 +24,18 @@
   toolchains = pw_target_toolchain_stm32h753zi_nucleo_list
 }
 
+config("module_config_options") {
+  cflags = [
+    "-include",
+    rebase_path("module_config_overrides.h", root_build_dir),
+  ]
+}
+
+pw_source_set("module_config_overrides") {
+  public_configs = [ ":module_config_options" ]
+  sources = [ "module_config_overrides.h" ]
+}
+
 if (current_toolchain != default_toolchain) {
   pw_source_set("pre_init") {
     public_deps = [ "$dir_pw_sys_io_stm32cube" ]
diff --git a/targets/stm32h753zi-nucleo/module_config_overrides.h b/targets/stm32h753zi-nucleo/module_config_overrides.h
new file mode 100644
index 0000000..b73e0d6
--- /dev/null
+++ b/targets/stm32h753zi-nucleo/module_config_overrides.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// Configure the UART for pw_sys_io_stm32cube.
+#define PW_SYS_IO_STM32CUBE_USART_NUM 3
+#define PW_SYS_IO_STM32CUBE_GPIO_PORT D
+#define PW_SYS_IO_STM32CUBE_GPIO_TX_PIN 8
+#define PW_SYS_IO_STM32CUBE_GPIO_RX_PIN 9
diff --git a/targets/stm32h753zi-nucleo/target_toolchains.gni b/targets/stm32h753zi-nucleo/target_toolchains.gni
index f142cfa..6945b99 100644
--- a/targets/stm32h753zi-nucleo/target_toolchains.gni
+++ b/targets/stm32h753zi-nucleo/target_toolchains.gni
@@ -59,10 +59,8 @@
       "$dir_pw_sync_baremetal:interrupt_spin_lock"
   pw_log_BACKEND = dir_pw_log_basic
   pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube
-  pw_sys_io_stm32cube_usart_num = "3"
-  pw_sys_io_stm32cube_gpio_port = "D"
-  pw_sys_io_stm32cube_gpio_tx_pin = "8"
-  pw_sys_io_stm32cube_gpio_rx_pin = "9"
+  pw_sys_io_stm32cube_CONFIG =
+      "//targets/stm32h753zi-nucleo:module_config_overrides"
 
   #TODO: remove dependency on stm32f429i-disc1 rpc server.
   pw_rpc_system_server_BACKEND =
diff --git a/targets/stm32l552ze-nucleo/BUILD.gn b/targets/stm32l552ze-nucleo/BUILD.gn
index 4c20aee..815cc40 100644
--- a/targets/stm32l552ze-nucleo/BUILD.gn
+++ b/targets/stm32l552ze-nucleo/BUILD.gn
@@ -24,6 +24,18 @@
   toolchains = pw_target_toolchain_stm32l552ze_nucleo_list
 }
 
+config("module_config_options") {
+  cflags = [
+    "-include",
+    rebase_path("module_config_overrides.h", root_build_dir),
+  ]
+}
+
+pw_source_set("module_config_overrides") {
+  public_configs = [ ":module_config_options" ]
+  sources = [ "module_config_overrides.h" ]
+}
+
 if (current_toolchain != default_toolchain) {
   pw_source_set("pre_init") {
     public_deps = [ "$dir_pw_sys_io_stm32cube" ]
diff --git a/targets/stm32l552ze-nucleo/module_config_overrides.h b/targets/stm32l552ze-nucleo/module_config_overrides.h
new file mode 100644
index 0000000..49d6ab7
--- /dev/null
+++ b/targets/stm32l552ze-nucleo/module_config_overrides.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// Configure the UART for pw_sys_io_stm32cube.
+#define PW_SYS_IO_STM32CUBE_USART_NUM 1
+#define PW_SYS_IO_STM32CUBE_GPIO_PORT G
+#define PW_SYS_IO_STM32CUBE_GPIO_TX_PIN 7
+#define PW_SYS_IO_STM32CUBE_GPIO_RX_PIN 8
diff --git a/targets/stm32l552ze-nucleo/target_toolchains.gni b/targets/stm32l552ze-nucleo/target_toolchains.gni
index ce84684..2531419 100644
--- a/targets/stm32l552ze-nucleo/target_toolchains.gni
+++ b/targets/stm32l552ze-nucleo/target_toolchains.gni
@@ -59,10 +59,8 @@
       "$dir_pw_sync_baremetal:interrupt_spin_lock"
   pw_log_BACKEND = dir_pw_log_basic
   pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube
-  pw_sys_io_stm32cube_usart_num = "1"
-  pw_sys_io_stm32cube_gpio_port = "G"
-  pw_sys_io_stm32cube_gpio_tx_pin = "7"
-  pw_sys_io_stm32cube_gpio_rx_pin = "8"
+  pw_sys_io_stm32cube_CONFIG =
+      "//targets/stm32l552ze-nucleo:module_config_overrides"
 
   #TODO: remove dependency on stm32f429i-disc1 rpc server.
   pw_rpc_system_server_BACKEND =