pw_sys_io_stm32cube: Add module

Moves pw_sys_io_stm32cube from experimental to Pigweed core.

Requires: 73181
Change-Id: I36170562671153488f2b54f954aa0970aac09063
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/72961
Pigweed-Auto-Submit: Armando Montanez <amontanez@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_sys_io_stm32cube/BUILD.gn b/pw_sys_io_stm32cube/BUILD.gn
new file mode 100644
index 0000000..6b9c439
--- /dev/null
+++ b/pw_sys_io_stm32cube/BUILD.gn
@@ -0,0 +1,58 @@
+# Copyright 2021 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.
+
+import("//build_overrides/pigweed.gni")
+
+import("$dir_pw_build/target_types.gni")
+import("$dir_pw_docgen/docs.gni")
+
+# Defaults to USART1 on the STM32F429xx, but can be overridden.
+declare_args() {
+  # USART to use for sys_io
+  pw_sys_io_stm32cube_usart_num = "1"
+
+  # GPIO Port of the specified USART
+  pw_sys_io_stm32cube_gpio_port = "A"
+
+  # GPIO Pin for tx
+  pw_sys_io_stm32cube_gpio_tx_pin = "9"
+
+  # GPIO Pin for rx
+  pw_sys_io_stm32cube_gpio_rx_pin = "10"
+}
+
+config("public_includes") {
+  include_dirs = [ "public" ]
+}
+
+pw_source_set("pw_sys_io_stm32cube") {
+  defines = [
+    "USART_NUM=$pw_sys_io_stm32cube_usart_num",
+    "USART_GPIO_PORT_CHAR=$pw_sys_io_stm32cube_gpio_port",
+    "USART_TX_PIN_NUM=$pw_sys_io_stm32cube_gpio_tx_pin",
+    "USART_RX_PIN_NUM=$pw_sys_io_stm32cube_gpio_rx_pin",
+  ]
+  public_configs = [ ":public_includes" ]
+  public_deps = [
+    "$dir_pw_preprocessor",
+    "$dir_pw_status",
+    "$dir_pw_third_party/stm32cube",
+  ]
+  public = [ "public/pw_sys_io_stm32cube/init.h" ]
+  sources = [ "sys_io.cc" ]
+  deps = [
+    "$dir_pw_sys_io:default_putget_bytes",
+    "$dir_pw_sys_io:facade",
+  ]
+}