Add Zephyr port

This port is meant to grow to encompass all existing boards. For
now, it is a port while we transition over.

It is named `zephyr-cp` to differentiate it from the MicroPython
`zephyr` port. They are separate implementations.

Author: tannewt

.gitmodules

@@ -410,3 +410,6 @@
 [submodule "ports/analog/msdk"]
 	path = ports/analog/msdk
 	url = https://github.com/analogdevicesinc/msdk.git
+[submodule "lib/zephyr"]
+	path = ports/zephyr-cp/lib/zephyr
+	url = https://github.com/zephyrproject-rtos/zephyr.git

CONTRIBUTING.md

@@ -44,6 +44,28 @@ Build Documentation:
 
 - For SAMD21 debugging workflow tips check out [this learn guide](https://learn.adafruit.com/debugging-the-samd21-with-gdb) from Scott (@tannewt).
 
+### CircuitPython is built on top of Zephyr
+
+First, install Zephyr tools (see [Zephyr's Getting Started Guide](https://docs.zephyrproject.org/4.0.0/develop/getting_started/index.html)). (These are `fish` commands because that's what Scott uses.)
+
+
+```sh
+pip install west
+west update
+west zephyr-export
+pip install -r lib/zephyr/scripts/requirements.txt
+env ZEPHYR_BASE=lib/zephyr west sdk install
+```
+
+Now to build from the top level:
+
+```sh
+west build -b pca10056 -o=-j32 -- -G'Unix Makefiles'  -DCMAKE_VERBOSE_MAKEFILE=ON
+```
+
+This uses Zephyr's cmake to generate Makefiles that then delegate to
+`tools/cpbuild/build_circuitpython.py` to build the CircuitPython bits in parallel.
+
 ## Developer contacts
 Scott Shawcroft ([@tannewt](https://github.com/tannewt)) is the lead developer of CircuitPython
 and is sponsored by [Adafruit Industries LLC](https://adafruit.com). Scott is usually available

main.c

@@ -974,7 +974,13 @@ static int run_repl(safe_mode_t safe_mode) {
     return exit_code;
 }
 
+#if defined(__ZEPHYR__) && __ZEPHYR__ == 1
+#include <zephyr/console/console.h>
+
+int circuitpython_main(void) {
+#else
 int __attribute__((used)) main(void) {
+    #endif
 
     // initialise the cpu and peripherals
     set_safe_mode(port_init());
@@ -991,14 +997,19 @@ int __attribute__((used)) main(void) {
     common_hal_nvm_bytearray_set_bytes(&common_hal_mcu_nvm_obj, 0, &value_out, 1);
     #endif
 
+    printk("serial_early_init\r\n");
+
     // Start the debug serial
     serial_early_init();
+
     mp_hal_stdout_tx_str(line_clear);
 
     // Wait briefly to give a reset window where we'll enter safe mode after the reset.
     if (get_safe_mode() == SAFE_MODE_NONE) {
         set_safe_mode(wait_for_safe_mode_reset());
     }
+    printk("safe_mode: %d\r\n", get_safe_mode());
+
 
     stack_init();
 

ports/zephyr-cp/.gitignore

@@ -0,0 +1,5 @@
+# West manages these folders.
+bootloader
+build
+modules
+tools

ports/zephyr-cp/.west/config

@@ -0,0 +1,3 @@
+[manifest]
+path = lib/zephyr
+file = west.yml

ports/zephyr-cp/CMakeLists.txt

@@ -0,0 +1,60 @@
+cmake_minimum_required(VERSION 3.20.0)
+
+set(ZEPHYR_BOARD_ALIASES boards/board_aliases.cmake)
+
+find_package(Zephyr REQUIRED HINTS ../../lib/zephyr)
+project(circuitpython)
+
+target_sources(app PRIVATE zephyr_main.c)
+
+# From: https://github.com/zephyrproject-rtos/zephyr/blob/main/samples/application_development/external_lib/CMakeLists.txt
+# The external static library that we are linking with does not know
+# how to build for this platform so we export all the flags used in
+# this zephyr build to the external build system.
+#
+# Other external build systems may be self-contained enough that they
+# do not need any build information from zephyr. Or they may be
+# incompatible with certain zephyr options and need them to be
+# filtered out.
+zephyr_get_include_directories_for_lang_as_string(       C includes)
+zephyr_get_system_include_directories_for_lang_as_string(C system_includes)
+zephyr_get_compile_definitions_for_lang_as_string(       C definitions)
+zephyr_get_compile_options_for_lang_as_string(           C options)
+
+if(DEFINED CMAKE_C_COMPILER_TARGET)
+  set(target_flag "--target=${CMAKE_C_COMPILER_TARGET}")
+endif()
+
+set(external_project_cflags
+  "${target_flag} ${includes} ${definitions} ${options} ${system_includes}"
+  )
+
+ExternalProject_Add(circuitpython
+    DOWNLOAD_COMMAND ""
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND python ${CMAKE_CURRENT_SOURCE_DIR}/cptools/build_circuitpython.py
+    CC=${CMAKE_C_COMPILER}
+    AR=${CMAKE_AR}
+    CFLAGS=${external_project_cflags}
+    BOARD=${BOARD}
+    BOARD_ALIAS=${BOARD_ALIAS}
+    BOARD_REVISION=${BOARD_REVISION}
+    BOARD_QUALIFIERS=${BOARD_QUALIFIERS}
+    SOC_DIRECTORIES=${SOC_DIRECTORIES}
+    OUTPUT_FILE=${CMAKE_CURRENT_BINARY_DIR}/libcircuitpython.a
+    PORT_SRC_DIR=${CMAKE_CURRENT_SOURCE_DIR}
+    BUILD_BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/libcircuitpython.a
+    BUILD_JOB_SERVER_AWARE TRUE
+    BUILD_ALWAYS TRUE
+    DEPENDS zephyr
+    INSTALL_COMMAND ""
+    )
+
+add_library(circuitpython_wrapper STATIC IMPORTED GLOBAL)
+add_dependencies(
+  circuitpython_wrapper
+  circuitpython
+  )
+set_target_properties(circuitpython_wrapper PROPERTIES IMPORTED_LOCATION             ${CMAKE_CURRENT_BINARY_DIR}/libcircuitpython.a)
+target_link_libraries(circuitpython_wrapper INTERFACE kernel)
+target_link_libraries(app PRIVATE circuitpython_wrapper)

ports/zephyr-cp/README.md

@@ -0,0 +1,28 @@
+# Zephyr
+
+This is an initial port of CircuitPython onto Zephyr. We intend on migrating all
+existing boards onto Zephyr. To start, we'll only support new boards. Existing
+boards will be switched as the Zephyr port reaches parity with the existing
+implementation.
+
+## Getting Started
+
+First, install Zephyr tools (see [Zephyr's Getting Started Guide](https://docs.zephyrproject.org/4.0.0/develop/getting_started/index.html)). (These are `fish` commands because that's what Scott uses.)
+
+
+```sh
+pip install west
+west update
+west zephyr-export
+pip install -r lib/zephyr/scripts/requirements.txt
+env ZEPHYR_BASE=lib/zephyr west sdk install
+```
+
+Now to build from the top level:
+
+```sh
+west build -b pca10056 -o=-j32 -- -G'Unix Makefiles'
+```
+
+This uses Zephyr's cmake to generate Makefiles that then delegate to
+`tools/cpbuild/build_circuitpython.py` to build the CircuitPython bits in parallel.

ports/zephyr-cp/background.c

@@ -0,0 +1,45 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#include "background.h"
+
+#include "py/runtime.h"
+#include "supervisor/port.h"
+
+#if CIRCUITPY_DISPLAYIO
+#include "shared-module/displayio/__init__.h"
+#endif
+
+#if CIRCUITPY_AUDIOBUSIO
+#include "common-hal/audiobusio/I2SOut.h"
+#endif
+
+#if CIRCUITPY_AUDIOPWMIO
+#include "common-hal/audiopwmio/PWMAudioOut.h"
+#endif
+
+void port_start_background_tick(void) {
+}
+
+void port_finish_background_tick(void) {
+}
+
+void port_background_tick(void) {
+    #if CIRCUITPY_AUDIOPWMIO
+    audiopwmout_background();
+    #endif
+    #if CIRCUITPY_AUDIOBUSIO
+    i2s_background();
+    #endif
+}
+
+// Allow boards to override this.
+MP_WEAK void board_background_task(void) {
+}
+
+void port_background_task(void) {
+    board_background_task();
+}

ports/zephyr-cp/background.h

@@ -0,0 +1,9 @@
+// This file is part of the CircuitPython project: https://circuitpython.org
+//
+// SPDX-FileCopyrightText: Copyright (c) 2019 Dan Halbert for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+void board_background_task(void);

ports/zephyr-cp/boards/board_aliases.cmake

@@ -0,0 +1 @@
+set(pca10056_BOARD_ALIAS nrf52840dk/nrf52840)