Compiled and linked SAMD21x18 version successfully.

atmel-samd/Makefile

@@ -0,0 +1,93 @@
+include ../py/mkenv.mk
+
+CROSS = 0
+
+# qstr definitions (must come before including py.mk)
+QSTR_DEFS = qstrdefsport.h
+
+# include py core make definitions
+include ../py/py.mk
+
+ifeq ($(CROSS), 1)
+CROSS_COMPILE = arm-none-eabi-
+endif
+
+BOSSAC := /Users/tannewt/ArduinoCore-samd/tools/bossac_osx
+
+INC += -I.
+INC += -I..
+INC += -I../lib/mp-readline
+INC += -I$(BUILD)
+
+ifeq ($(CROSS), 1)
+CFLAGS_CORTEX_M0 = -mthumb -mabi=aapcs-linux -mcpu=cortex-m0plus -fsingle-precision-constant -Wdouble-promotion -D__SAMD21G18A__
+CFLAGS = $(INC) -Wall -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M0) $(COPT)
+else
+CFLAGS = -m32 $(INC) -Wall -Werror -ansi -std=gnu99 $(COPT)
+endif
+
+#Debugging/Optimization
+ifeq ($(DEBUG), 1)
+CFLAGS += -O0 -ggdb
+else
+CFLAGS += -Os -DNDEBUG
+endif
+
+LIBS =
+ifeq ($(CROSS), 1)
+LIBGCC_FILE_NAME = $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+LDFLAGS = -Lasf/thirdparty/CMSIS/Lib/GCC/ -L $(dir $(LIBGCC_FILE_NAME)) -nostdlib -T samd21.ld -Map=$@.map --cref
+LIBS += -larm_cortexM0l_math -lgcc
+else
+LD = gcc
+LDFLAGS = -m32 -Wl,-Map=$@.map,--cref
+endif
+
+SRC_C = \
+	main.c \
+	uart_core.c \
+	lib/utils/stdout_helpers.c \
+	lib/utils/printf.c \
+	lib/utils/pyexec.c \
+	lib/libc/string0.c \
+	lib/mp-readline/readline.c \
+	$(BUILD)/_frozen_mpy.c \
+
+OBJ = $(PY_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
+
+ifeq ($(CROSS), 1)
+all: $(BUILD)/firmware.bin
+else
+all: $(BUILD)/firmware.elf
+endif
+
+$(BUILD)/_frozen_mpy.c: frozentest.mpy $(BUILD)/genhdr/qstrdefs.generated.h
+	$(ECHO) "MISC freezing bytecode"
+	$(Q)../tools/mpy-tool.py -f -q $(BUILD)/genhdr/qstrdefs.preprocessed.h -mlongint-impl=none $< > $@
+
+$(BUILD)/firmware.elf: $(OBJ)
+	$(ECHO) "LINK $@"
+	$(Q)$(LD) $(LDFLAGS) -o $@ $^ $(LIBS)
+	$(Q)$(SIZE) $@
+
+$(BUILD)/firmware.bin: $(BUILD)/firmware.elf
+	$(ECHO) "Create $@"
+	$(Q)$(OBJCOPY) -O binary -j .isr_vector -j .text -j .data $^ $@
+
+deploy: $(BUILD)/firmware.bin
+	$(ECHO) "Writing $< to the board"
+	$(BOSSAC) -u $<
+
+# Run emulation build on a POSIX system with suitable terminal settings
+run:
+	stty raw opost -echo
+	build/firmware.elf
+	@echo Resetting terminal...
+# This sleep is useful to spot segfaults
+	sleep 1
+	reset
+
+test: $(BUILD)/firmware.elf
+	$(Q)/bin/echo -e "print('hello world!', list(x+1 for x in range(10)), end='eol\\\\n')\\r\\n\\x04" | $(BUILD)/firmware.elf | tail -n2 | grep "^hello world! \\[1, 2, 3, 4, 5, 6, 7, 8, 9, 10\\]eol"
+
+include ../py/mkrules.mk

atmel-samd/README.md

@@ -0,0 +1,17 @@
+# SAMD21x18
+
+This port is intended to be a full featured MicroPython port for SAMD21x18 based
+development boards including the Arduino Zero, Adafruit Feather M0 and Adafruit
+M0 BLE.
+
+## Building for a SAMD21x18 MCU
+
+The Makefile has the ability to build for a SAMD21x18, and by default
+includes some start-up code and also enables a UART for communication.  To build:
+
+    $ make CROSS=1
+
+If you previously built the Linux version, you will need to first run
+`make clean` to get rid of incompatible object files.
+
+Deploying coming soon!

atmel-samd/asf/readme.txt

@@ -0,0 +1,125 @@
+1 - Introduction
+----------------
+
+The Atmel® Software Framework (ASF) is a collection of embedded software for Atmel flash MCU (www.atmel.com/asf).
+» It simplifies the usage of microcontrollers, providing an abstraction to the hardware and high-value middlewares
+» ASF is designed to be used for evaluation, prototyping, design and production phases
+» ASF is integrated in the Atmel Studio IDE with a graphical user interface or available as standalone for GCC, IAR compilers
+» ASF can be downloaded for free
+
+ASF online documentation can be found here: http://asf.atmel.com
+
+Supported devices:
+» AVR UC3(Trade Mark) (http://www.atmel.com/products/microcontrollers/avr/32-bitavruc3.aspx)
+» AVR XMEGA(Trade Mark) (http://www.atmel.com/products/microcontrollers/avr/avr_xmega.aspx) 
+» megaAVR(Trade Mark) (http://www.atmel.com/products/microcontrollers/avr/megaavr.aspx) 
+» SAM (http://www.atmel.com/products/microcontrollers/arm/default.aspx)
+
+Each software module is provided with full source code, example of usage and
+ready-to-use projects for the IAR EW and GNU GCC compilers.
+
+This package is dedicated for IAR and GCC makefile users. AVR Studio 5 or Atmel Studio 6 users do not
+need this package as the ASF is integrated in Atmel Studio.
+
+The top folder organization is as follow:
+- the avr32/ folder contains software modules(source code and projects) dedicated to AVR UC3 devices,
+- the mega/ folder contains software modules(source code and projects) dedicated to megaAVR devices,
+- the xmega/ folder contains software modules(source code and projects) dedicated to AVR XMEGA devices,
+- the sam/ folder contains software modules(source code and projects) dedicated to SAM devices,
+- the common/ folder contains software modules(source code and projects) shared by all AVR and SAM devices,
+- the thirdparty/ folder contains software modules(source code and projects) from thirdparty providers for all Atmel devices.
+
+The thirdparty/ folder is organized by thirdparty software module (i.e. one folder per thirdparty software module).
+
+The avr32/, xmega/, mega/, sam/ and common/ folders are organized as follow:
+- the drivers/ folder contains low-level software drivers for MCU on-chip resources (eg cpu, usart, adc drivers).
+- the boards/ folder contains board-specific source code files.
+- the utils/ folder contains files that are used by all other modules: it holds
+several linker script files, IAR & GCC pre-compiled libraries of some ASF modules,
+and C/C++ utility files with general usage defines, macros and functions.
+- the services/ folder contains application-oriented pieces of software that are
+not specific to boards nor chips (eg. FAT, TCP/IP stack, os, JPEG decoder).
+For the common/ top folder, the services/ folder also contains chip-specific code.
+- the components/ folder offers, for each supported hardware component, a software
+interface to interact with the component (eg memories like SDRAM, SD card, or display)
+- the applications/ contains hefty examples of applications using services and drivers.
+
+
+2 - Documentation
+--------------------------
+
+ASF release notes, reference manual and getting started documents can be found on http://www.atmel.com/asf.
+
+The ASF documentation can be found online on http://asf.atmel.com.
+
+
+3 - Toolchain Header Files Update
+---------------------------------
+
+For 8-bit AVR users it is recommended to update the toolchain header files, a
+description about how to do that is located in the readme.txt file under the
+xmega/utils/header_files/ directory.
+
+For AVR UC3 users using IAR, it is recommended to update the IAR header files.
+To do that, unzip the avr32-headers.zip file (located under
+the avr32/utils/header_files/ directory) to the IAR EWAVR32 installation folder
+under "IAR installation folder"/Embedded Workbench x.y/avr32/inc/.
+
+
+4 - IAR EW Users
+----------------
+
+Using an example of usage of the AVR UC3 GPIO driver module as an example, the
+IAR projects are located under:
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3a0512_evk1000/iar/ for an EVK1100 board,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3a0512_evk1105/iar/ for an EVK1105 board,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3b0256_evk1101/iar/ for an EVK1101 board,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3a3256_evk1104/iar/ for an EVK1104 board,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3l064_stk600-rcuc3l0/iar/ for an STK600-RCUC3L0 setup,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3c0512c_uc3c_ek/iar/ for an AT32UC3C-EK board,
+- avr32/drivers/gpio/peripheral_bus_example/at32uc3l064_uc3l_ek/iar/ for an AT32UC3L-EK board.
+
+Each iar folder contains a full IAR project with:
+- an IAR EWAVR32 workspace file(avr32_drivers_gpio_peripheral_bus_example_uc3l_ek.eww: double-click on this file to open the whole project),
+- an IAR EWAVR32 project file(avr32_drivers_gpio_peripheral_bus_example_uc3l_ek.ewp),
+- an IAR EWAVR32 debug configuration file(avr32_drivers_gpio_peripheral_bus_example_uc3l_ek.ewd).
+
+
+5 - AVR32 Studio Users
+----------------------
+
+It is possible to work with an unzipped ASF package from within AVR32 Studio: this
+is described in the application note "AVR32769: How to Compile the standalone AVR
+UC3 Software Framework in AVR32 Studio V2": http://www.atmel.com/dyn/resources/prod_documents/doc32115.pdf
+
+
+6 - Offline documentation - Generating The HTML Documentation
+-------------------------------------
+
+All modules are fully documented using doxygen tags. Each project within the ASF
+contains a doxyfile.doxygen (used to configure doxygen for a proper documentation
+generation): to generate the html documentation, doxygen must be installed (see
+http://www.doxygen.org/download.html) and the doxyfile.doxygen must be used as
+the input configuration file for doxygen.
+
+Using an example of usage of the AVR UC3 GPIO driver module as an example, for
+an AT32UC3C-EK board, the associated doxyfile.doxygen file is under the
+avr32/drivers/gpio/peripheral_bus_example/at32uc3c0512c_uc3c_ek/doxygen/ folder.
+Run doxygen and use this doxyfile.doxygen as configuration file for doxygen.
+Using the command line, this is done with the following command: doxygen doxyfile.doxygen
+
+
+7 - Contact Information
+-----------------------
+
+For more info about Atmel MCU visit http://www.atmel.com/products/microcontrollers/default.aspx or contact support through the http://support.atmel.no/ site.
+The support site also have a Frequently Asked Questions page with the most common questions.
+
+ASF bugs or enhancement requests can be reported in the ASF Bug Tracker (http://asf.atmel.com/bugzilla/).
+
+
+8 - Community Information
+-------------------------
+
+Users can find an ASF forum (http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewforum&f=21) on AVRfreaks for AVR users or on http://www.at91.com/ for SAM users.
+This forum can be used to have an open discussion about usage, development, bugs, fixes, improvements, etc.

atmel-samd/frozentest.py

@@ -0,0 +1,7 @@
+print('uPy')
+print('a long string that is not interned')
+print('a string that has unicode αβγ chars')
+print(b'bytes 1234\x01')
+print(123456789)
+for i in range(4):
+    print(i)

atmel-samd/main.c

@@ -0,0 +1,167 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "py/nlr.h"
+#include "py/compile.h"
+#include "py/runtime.h"
+#include "py/repl.h"
+#include "py/gc.h"
+#include "lib/utils/pyexec.h"
+
+void do_str(const char *src, mp_parse_input_kind_t input_kind) {
+    mp_lexer_t *lex = mp_lexer_new_from_str_len(MP_QSTR__lt_stdin_gt_, src, strlen(src), 0);
+    if (lex == NULL) {
+        printf("MemoryError: lexer could not allocate memory\n");
+        return;
+    }
+
+    nlr_buf_t nlr;
+    if (nlr_push(&nlr) == 0) {
+        qstr source_name = lex->source_name;
+        mp_parse_tree_t parse_tree = mp_parse(lex, input_kind);
+        mp_obj_t module_fun = mp_compile(&parse_tree, source_name, MP_EMIT_OPT_NONE, true);
+        mp_call_function_0(module_fun);
+        nlr_pop();
+    } else {
+        // uncaught exception
+        mp_obj_print_exception(&mp_plat_print, (mp_obj_t)nlr.ret_val);
+    }
+}
+
+static char *stack_top;
+static char heap[2048];
+
+int main(int argc, char **argv) {
+    int stack_dummy;
+    stack_top = (char*)&stack_dummy;
+
+    #if MICROPY_ENABLE_GC
+    gc_init(heap, heap + sizeof(heap));
+    #endif
+    mp_init();
+    #if MICROPY_REPL_EVENT_DRIVEN
+    pyexec_event_repl_init();
+    for (;;) {
+        int c = mp_hal_stdin_rx_chr();
+        if (pyexec_event_repl_process_char(c)) {
+            break;
+        }
+    }
+    #else
+    pyexec_friendly_repl();
+    #endif
+    //do_str("print('hello world!', list(x+1 for x in range(10)), end='eol\\n')", MP_PARSE_SINGLE_INPUT);
+    //do_str("for i in range(10):\r\n  print(i)", MP_PARSE_FILE_INPUT);
+    mp_deinit();
+    return 0;
+}
+
+void gc_collect(void) {
+    // WARNING: This gc_collect implementation doesn't try to get root
+    // pointers from CPU registers, and thus may function incorrectly.
+    void *dummy;
+    gc_collect_start();
+    gc_collect_root(&dummy, ((mp_uint_t)stack_top - (mp_uint_t)&dummy) / sizeof(mp_uint_t));
+    gc_collect_end();
+    gc_dump_info();
+}
+
+mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
+    return NULL;
+}
+
+mp_import_stat_t mp_import_stat(const char *path) {
+    return MP_IMPORT_STAT_NO_EXIST;
+}
+
+mp_obj_t mp_builtin_open(uint n_args, const mp_obj_t *args, mp_map_t *kwargs) {
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
+
+void nlr_jump_fail(void *val) {
+}
+
+void NORETURN __fatal_error(const char *msg) {
+    while (1);
+}
+
+#ifndef NDEBUG
+void MP_WEAK __assert_func(const char *file, int line, const char *func, const char *expr) {
+    printf("Assertion '%s' failed, at file %s:%d\n", expr, file, line);
+    __fatal_error("Assertion failed");
+}
+#endif
+
+#if MICROPY_MIN_USE_CORTEX_CPU
+
+// this is a minimal IRQ and reset framework for any Cortex-M CPU
+
+extern uint32_t _estack, _sidata, _sdata, _edata, _sbss, _ebss;
+
+void Reset_Handler(void) __attribute__((naked));
+void Reset_Handler(void) {
+    // stack pointer set by bootloader
+    // copy .data section from flash to RAM
+    for (uint32_t *src = &_sidata, *dest = &_sdata; dest < &_edata;) {
+        *dest++ = *src++;
+    }
+    // zero out .bss section
+    for (uint32_t *dest = &_sbss; dest < &_ebss;) {
+        *dest++ = 0;
+    }
+    // jump to board initialisation
+    void _start(void);
+    _start();
+}
+
+void Default_Handler(void) {
+    for (;;) {
+    }
+}
+
+uint32_t isr_vector[] __attribute__((section(".isr_vector"))) = {
+    (uint32_t)&_estack,
+    (uint32_t)&Reset_Handler,
+    (uint32_t)&Default_Handler, // NMI_Handler
+    (uint32_t)&Default_Handler, // HardFault_Handler
+    (uint32_t)&Default_Handler, // MemManage_Handler
+    (uint32_t)&Default_Handler, // BusFault_Handler
+    (uint32_t)&Default_Handler, // UsageFault_Handler
+    0,
+    0,
+    0,
+    0,
+    (uint32_t)&Default_Handler, // SVC_Handler
+    (uint32_t)&Default_Handler, // DebugMon_Handler
+    0,
+    (uint32_t)&Default_Handler, // PendSV_Handler
+    (uint32_t)&Default_Handler, // SysTick_Handler
+};
+
+void _start(void) {
+    // when we get here: stack is initialised, bss is clear, data is copied
+
+    // initialise the cpu and peripherals
+    #if MICROPY_MIN_USE_SAMD21_MCU
+    void samd21_init(void);
+    samd21_init();
+    #endif
+
+    // now that we have a basic system up and running we can call main
+    main(0, NULL);
+
+    // we must not return
+    for (;;) {
+    }
+}
+
+#endif
+
+#if MICROPY_MIN_USE_SAMD21_MCU
+
+void samd21_init(void) {
+}
+
+#endif

atmel-samd/mpconfigport.h

@@ -0,0 +1,95 @@
+#include <stdint.h>
+
+// options to control how Micro Python is built
+
+#define MICROPY_QSTR_BYTES_IN_HASH  (1)
+#define MICROPY_QSTR_EXTRA_POOL     mp_qstr_frozen_const_pool
+#define MICROPY_ALLOC_PATH_MAX      (256)
+#define MICROPY_ALLOC_PARSE_CHUNK_INIT (16)
+#define MICROPY_EMIT_X64            (0)
+#define MICROPY_EMIT_THUMB          (0)
+#define MICROPY_EMIT_INLINE_THUMB   (0)
+#define MICROPY_COMP_MODULE_CONST   (0)
+#define MICROPY_COMP_CONST          (0)
+#define MICROPY_COMP_DOUBLE_TUPLE_ASSIGN (0)
+#define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (0)
+#define MICROPY_MEM_STATS           (0)
+#define MICROPY_DEBUG_PRINTERS      (0)
+#define MICROPY_ENABLE_GC           (1)
+#define MICROPY_GC_ALLOC_THRESHOLD  (0)
+#define MICROPY_REPL_EVENT_DRIVEN   (0)
+#define MICROPY_HELPER_REPL         (1)
+#define MICROPY_HELPER_LEXER_UNIX   (0)
+#define MICROPY_ENABLE_SOURCE_LINE  (0)
+#define MICROPY_ENABLE_DOC_STRING   (0)
+#define MICROPY_ERROR_REPORTING     (MICROPY_ERROR_REPORTING_TERSE)
+#define MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG (0)
+#define MICROPY_PY_ASYNC_AWAIT      (0)
+#define MICROPY_PY_BUILTINS_BYTEARRAY (0)
+#define MICROPY_PY_BUILTINS_MEMORYVIEW (0)
+#define MICROPY_PY_BUILTINS_ENUMERATE (0)
+#define MICROPY_PY_BUILTINS_FILTER  (0)
+#define MICROPY_PY_BUILTINS_FROZENSET (0)
+#define MICROPY_PY_BUILTINS_REVERSED (0)
+#define MICROPY_PY_BUILTINS_SET     (0)
+#define MICROPY_PY_BUILTINS_SLICE   (0)
+#define MICROPY_PY_BUILTINS_PROPERTY (0)
+#define MICROPY_PY_BUILTINS_MIN_MAX (0)
+#define MICROPY_PY___FILE__         (0)
+#define MICROPY_PY_GC               (0)
+#define MICROPY_PY_ARRAY            (0)
+#define MICROPY_PY_ATTRTUPLE        (0)
+#define MICROPY_PY_COLLECTIONS      (0)
+#define MICROPY_PY_MATH             (0)
+#define MICROPY_PY_CMATH            (0)
+#define MICROPY_PY_IO               (0)
+#define MICROPY_PY_STRUCT           (0)
+#define MICROPY_PY_SYS              (0)
+#define MICROPY_MODULE_FROZEN_MPY   (1)
+#define MICROPY_CPYTHON_COMPAT      (0)
+#define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_NONE)
+#define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_NONE)
+
+// type definitions for the specific machine
+
+#define BYTES_PER_WORD (4)
+
+#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p) | 1))
+
+// This port is intended to be 32-bit, but unfortunately, int32_t for
+// different targets may be defined in different ways - either as int
+// or as long. This requires different printf formatting specifiers
+// to print such value. So, we avoid int32_t and use int directly.
+#define UINT_FMT "%u"
+#define INT_FMT "%d"
+typedef int mp_int_t; // must be pointer size
+typedef unsigned mp_uint_t; // must be pointer size
+
+typedef long mp_off_t;
+
+#define MP_PLAT_PRINT_STRN(str, len) mp_hal_stdout_tx_strn_cooked(str, len)
+
+// extra built in names to add to the global namespace
+extern const struct _mp_obj_fun_builtin_t mp_builtin_open_obj;
+#define MICROPY_PORT_BUILTINS \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_open), (mp_obj_t)&mp_builtin_open_obj },
+
+// We need to provide a declaration/definition of alloca()
+#include <alloca.h>
+
+#define MICROPY_HW_BOARD_NAME "atmel-samd"
+#define MICROPY_HW_MCU_NAME "samd21"
+
+#ifdef __linux__
+#define MICROPY_MIN_USE_STDOUT (1)
+#endif
+
+#ifdef __thumb__
+#define MICROPY_MIN_USE_CORTEX_CPU (1)
+#define MICROPY_MIN_USE_STM32_MCU (1)
+#endif
+
+#define MP_STATE_PORT MP_STATE_VM
+
+#define MICROPY_PORT_ROOT_POINTERS \
+    const char *readline_hist[8];

atmel-samd/mphalport.h

@@ -0,0 +1,2 @@
+static inline mp_uint_t mp_hal_ticks_ms(void) { return 0; }
+static inline void mp_hal_set_interrupt_char(char c) {}

atmel-samd/qstrdefsport.h

@@ -0,0 +1 @@
+// qstrs specific to this port

atmel-samd/samd21.ld

@@ -0,0 +1,62 @@
+/*
+    GNU linker script for SAMD21
+*/
+
+/* Specify the memory areas */
+MEMORY
+{
+    FLASH (rx) : ORIGIN = 0x00000000+0x2000, LENGTH = 0x00040000-0x2000 /* First 8KB used by bootloader */
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
+}
+
+/* top end of the stack */
+_estack = ORIGIN(RAM) + LENGTH(RAM);
+
+/* define output sections */
+SECTIONS
+{
+    /* The program code and other data goes into FLASH */
+    .text :
+    {
+        . = ALIGN(4);
+        KEEP(*(.isr_vector)) /* isr vector table */
+        *(.text)           /* .text sections (code) */
+        *(.text*)          /* .text* sections (code) */
+        *(.rodata)         /* .rodata sections (constants, strings, etc.) */
+        *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
+
+        . = ALIGN(4);
+        _etext = .;        /* define a global symbol at end of code */
+        _sidata = _etext;  /* This is used by the startup in order to initialize the .data secion */
+    } >FLASH
+
+    /* This is the initialized data section
+    The program executes knowing that the data is in the RAM
+    but the loader puts the initial values in the FLASH (inidata).
+    It is one task of the startup to copy the initial values from FLASH to RAM. */
+    .data : AT ( _sidata )
+    {
+        . = ALIGN(4);
+        _sdata = .;        /* create a global symbol at data start; used by startup code in order to initialise the .data section in RAM */
+        *(.data)           /* .data sections */
+        *(.data*)          /* .data* sections */
+
+        . = ALIGN(4);
+        _edata = .;        /* define a global symbol at data end; used by startup code in order to initialise the .data section in RAM */
+    } >RAM
+
+    /* Uninitialized data section */
+    .bss :
+    {
+        . = ALIGN(4);
+        _sbss = .;         /* define a global symbol at bss start; used by startup code */
+        *(.bss)
+        *(.bss*)
+        *(COMMON)
+
+        . = ALIGN(4);
+        _ebss = .;         /* define a global symbol at bss end; used by startup code */
+    } >RAM
+
+    .ARM.attributes 0 : { *(.ARM.attributes) }
+}

atmel-samd/uart_core.c

@@ -0,0 +1,44 @@
+#include <unistd.h>
+#include "py/mpconfig.h"
+
+/*
+ * Core UART functions to implement for a port
+ */
+
+#if MICROPY_MIN_USE_STM32_MCU
+typedef struct {
+    volatile uint32_t SR;
+    volatile uint32_t DR;
+} periph_uart_t;
+#define USART1 ((periph_uart_t*)0x40011000)
+#endif
+
+// Receive single character
+int mp_hal_stdin_rx_chr(void) {
+    unsigned char c = 0;
+#if MICROPY_MIN_USE_STDOUT
+    int r = read(0, &c, 1);
+    (void)r;
+#elif MICROPY_MIN_USE_SAMD21_MCU
+    // wait for RXNE
+    while ((USART1->SR & (1 << 5)) == 0) {
+    }
+    c = USART1->DR;
+#endif
+    return c;
+}
+
+// Send string of given length
+void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
+#if MICROPY_MIN_USE_STDOUT
+    int r = write(1, str, len);
+    (void)r;
+#elif MICROPY_MIN_USE_SAMD21_MCU
+    while (len--) {
+        // wait for TXE
+        while ((USART1->SR & (1 << 7)) == 0) {
+        }
+        USART1->DR = *str++;
+    }
+#endif
+}