diff --git a/lib/micropython b/lib/micropython
index 294baf5..9feb068 160000
--- a/lib/micropython
+++ b/lib/micropython
@@ -1 +1 @@
-Subproject commit 294baf52b346e400e2255c6c1e82af5b978b18f7
+Subproject commit 9feb0689eeaca5ce88aedcc680f997a3b4d0221c
diff --git a/src/codal_app/microbithal.cpp b/src/codal_app/microbithal.cpp
index 258e4de..e21fdba 100644
--- a/src/codal_app/microbithal.cpp
+++ b/src/codal_app/microbithal.cpp
@@ -95,7 +95,7 @@ void microbit_hal_idle(void) {
     __WFI();
 }
 
-void microbit_hal_reset(void) {
+__attribute__((noreturn)) void microbit_hal_reset(void) {
     microbit_reset();
 }
 
diff --git a/src/codal_app/microbithal.h b/src/codal_app/microbithal.h
index ca137f3..e276bea 100644
--- a/src/codal_app/microbithal.h
+++ b/src/codal_app/microbithal.h
@@ -104,7 +104,7 @@ extern "C" {
 
 void microbit_hal_idle(void);
 
-void microbit_hal_reset(void);
+__attribute__((noreturn)) void microbit_hal_reset(void);
 void microbit_hal_panic(int);
 int microbit_hal_temperature(void);
 
diff --git a/src/codal_port/Makefile b/src/codal_port/Makefile
index 2d8d033..f7694e6 100644
--- a/src/codal_port/Makefile
+++ b/src/codal_port/Makefile
@@ -98,7 +98,6 @@ SRC_C += \
 	modradio.c \
 	modspeech.c \
 	modthis.c \
-	modutime.c \
 	mphalport.c \
 
 SRC_C += \
@@ -135,11 +134,7 @@ all: lib $(MBIT_VER_FILE)
 # Also rebuild MicroPython version header in correct directory to pick up git hash.
 $(MBIT_VER_FILE): FORCE
 	(cd $(TOP) && $(PYTHON) py/makeversionhdr.py $(abspath $(MP_VER_FILE)))
-	$(PYTHON) $(TOP)/py/makeversionhdr.py $(MBIT_VER_FILE).pre
-	$(CAT) $(MBIT_VER_FILE).pre | $(SED) s/MICROPY_/MICROBIT_/ > $(MBIT_VER_FILE)
-
-# Suppress warnings bulding stackctrl.c (fixed post v1.20.0).
-$(BUILD)/py/stackctrl.o: CWARN += -Wno-dangling-pointer
+	$(PYTHON) make_microbit_version_hdr.py $(MBIT_VER_FILE)
 
 # Suppress warnings from SAM library.
 $(BUILD)/$(abspath $(LOCAL_LIB_DIR))/sam/sam.o: CWARN += -Wno-array-bounds
diff --git a/src/codal_port/drv_image.c b/src/codal_port/drv_image.c
index 03f9e15..7e650b8 100644
--- a/src/codal_port/drv_image.c
+++ b/src/codal_port/drv_image.c
@@ -43,7 +43,7 @@ STATIC uint8_t monochrome_get_pixel(monochrome_5by5_t *self, mp_int_t x, mp_int_
 }
 
 greyscale_t *greyscale_new(mp_int_t w, mp_int_t h) {
-    greyscale_t *result = m_new_obj_var(greyscale_t, uint8_t, (w*h+1)>>1);
+    greyscale_t *result = m_new_obj_var(greyscale_t, byte_data, uint8_t, (w*h+1)>>1);
     result->base.type = &microbit_image_type;
     result->five = 0;
     result->width = w;
diff --git a/src/codal_port/main.c b/src/codal_port/main.c
index 500b9ad..8592e9b 100644
--- a/src/codal_port/main.c
+++ b/src/codal_port/main.c
@@ -36,7 +36,7 @@
 #include "shared/readline/readline.h"
 #include "shared/runtime/gchelper.h"
 #include "shared/runtime/pyexec.h"
-#include "ports/nrf/modules/uos/microbitfs.h"
+#include "ports/nrf/modules/os/microbitfs.h"
 #include "drv_softtimer.h"
 #include "drv_system.h"
 #include "drv_display.h"
@@ -136,7 +136,7 @@ void microbit_pyexec_file(const char *filename) {
     nlr_buf_t nlr;
     if (nlr_push(&nlr) == 0) {
         // Parse and comple the file.
-        mp_lexer_t *lex = mp_lexer_new_from_file(filename);
+        mp_lexer_t *lex = mp_lexer_new_from_file(qstr_from_str(filename));
         qstr source_name = lex->source_name;
         mp_parse_tree_t parse_tree = mp_parse(lex, MP_PARSE_FILE_INPUT);
         mp_obj_t module_fun = mp_compile(&parse_tree, source_name, false);
@@ -194,16 +194,16 @@ void microbit_file_opened_for_writing(const char *name, size_t name_len) {
 }
 
 #if MICROPY_MBFS
-mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
-    return uos_mbfs_new_reader(filename);
+mp_lexer_t *mp_lexer_new_from_file(qstr filename) {
+    return os_mbfs_new_reader(qstr_str(filename));
 }
 
 mp_import_stat_t mp_import_stat(const char *path) {
-    return uos_mbfs_import_stat(path);
+    return os_mbfs_import_stat(path);
 }
 
 mp_obj_t mp_builtin_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
-    return uos_mbfs_open(n_args, args);
+    return os_mbfs_open(n_args, args);
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
 #endif
diff --git a/src/codal_port/make_microbit_version_hdr.py b/src/codal_port/make_microbit_version_hdr.py
new file mode 100644
index 0000000..3d532ea
--- /dev/null
+++ b/src/codal_port/make_microbit_version_hdr.py
@@ -0,0 +1,120 @@
+"""
+Generate header file with macros defining micro:bit version info.
+
+Adapted from MicroPython's py/makeversionhdr.py file at v1.21.0.
+"""
+
+import argparse
+import sys
+import os
+import datetime
+import subprocess
+
+
+def get_version_info_from_git(repo_path):
+    # Note: git describe doesn't work if no tag is available
+    try:
+        git_tag = subprocess.check_output(
+            ["git", "describe", "--tags", "--dirty", "--always", "--match", "v[1-9].*"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+        ).strip()
+    except subprocess.CalledProcessError as er:
+        if er.returncode == 128:
+            # git exit code of 128 means no repository found
+            return None
+        git_tag = ""
+    except OSError:
+        return None
+    try:
+        git_hash = subprocess.check_output(
+            ["git", "rev-parse", "--short", "HEAD"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+        ).strip()
+    except subprocess.CalledProcessError:
+        git_hash = "unknown"
+    except OSError:
+        return None
+
+    try:
+        # Check if there are any modified files.
+        subprocess.check_call(
+            ["git", "diff", "--no-ext-diff", "--quiet", "--exit-code"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
+        )
+        # Check if there are any staged files.
+        subprocess.check_call(
+            ["git", "diff-index", "--cached", "--quiet", "HEAD", "--"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
+        )
+    except subprocess.CalledProcessError:
+        git_hash += "-dirty"
+    except OSError:
+        return None
+
+    return git_tag, git_hash
+
+
+def make_version_header(repo_path, filename):
+    info = None
+    if "MICROBIT_GIT_TAG" in os.environ:
+        info = [os.environ["MICROBIT_GIT_TAG"], os.environ["MICROBIT_GIT_HASH"]]
+    if info is None:
+        info = get_version_info_from_git(repo_path)
+
+    git_tag, git_hash = info
+
+    build_date = datetime.date.today()
+    if "SOURCE_DATE_EPOCH" in os.environ:
+        build_date = datetime.datetime.utcfromtimestamp(
+            int(os.environ["SOURCE_DATE_EPOCH"])
+        ).date()
+
+    # Generate the file with the git and version info
+    file_data = """\
+// This file was generated by py/makeversionhdr.py
+#define MICROBIT_GIT_TAG "%s"
+#define MICROBIT_GIT_HASH "%s"
+#define MICROBIT_BUILD_DATE "%s"
+""" % (
+        git_tag,
+        git_hash,
+        build_date.strftime("%Y-%m-%d"),
+    )
+
+    # Check if the file contents changed from last time
+    write_file = True
+    if os.path.isfile(filename):
+        with open(filename, "r") as f:
+            existing_data = f.read()
+        if existing_data == file_data:
+            write_file = False
+
+    # Only write the file if we need to
+    if write_file:
+        print("GEN %s" % filename)
+        with open(filename, "w") as f:
+            f.write(file_data)
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "-r",
+        "--repo-path",
+        default=os.path.join(os.path.dirname(sys.argv[0]), ".."),
+        help="path to git repo to query for version",
+    )
+    parser.add_argument("dest", nargs=1, help="output file path")
+    args = parser.parse_args()
+
+    make_version_header(args.repo_path, args.dest[0])
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/codal_port/microbitfs.c b/src/codal_port/microbitfs.c
index a192fab..308f208 100644
--- a/src/codal_port/microbitfs.c
+++ b/src/codal_port/microbitfs.c
@@ -1,5 +1,5 @@
 /*
- * This file is part of the Micro Python project, http://micropython.org/
+ * This file is part of the MicroPython project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
@@ -25,7 +25,7 @@
  * THE SOFTWARE.
  */
 
-// This is a copy of the file micropython:ports/nrf/modules/uos/microbitfs.c with:
+// This is a copy of the file micropython:ports/nrf/modules/os/microbitfs.c with:
 // - a call to `microbit_file_opened_for_writing` added in `microbit_file_open`
 // - a fix to `find_chunk_and_erase` to sweep the filesystem if any free chunks are found
 
@@ -33,7 +33,7 @@
 #include <stdio.h>
 #include <sys/stat.h>
 
-#include "modules/uos/microbitfs.h"
+#include "modules/os/microbitfs.h"
 #include "drivers/flash.h"
 #include "drivers/rng.h"
 #include "py/obj.h"
@@ -121,13 +121,13 @@ typedef struct _persistent_config_t {
     uint8_t marker; // Should always be PERSISTENT_DATA_MARKER
 } persistent_config_t;
 
-extern const mp_obj_type_t uos_mbfs_fileio_type;
-extern const mp_obj_type_t uos_mbfs_textio_type;
+extern const mp_obj_type_t os_mbfs_fileio_type;
+extern const mp_obj_type_t os_mbfs_textio_type;
 
 // Page indexes count down from the end of ROM.
 STATIC uint8_t first_page_index;
 STATIC uint8_t last_page_index;
-// The number of useable chunks in the file system.
+// The number of usable chunks in the file system.
 STATIC uint8_t chunks_in_file_system;
 // Index of chunk to start searches. This is randomised to even out wear.
 STATIC uint8_t start_index;
@@ -361,12 +361,7 @@ STATIC file_descriptor_obj *microbit_file_open(const char *name, size_t name_len
 }
 
 STATIC file_descriptor_obj *microbit_file_descriptor_new(uint8_t start_chunk, bool write, bool binary) {
-    file_descriptor_obj *res = m_new_obj(file_descriptor_obj);
-    if (binary) {
-        res->base.type = &uos_mbfs_fileio_type;
-    } else {
-        res->base.type = &uos_mbfs_textio_type;
-    }
+    file_descriptor_obj *res = mp_obj_malloc(file_descriptor_obj, binary ? &os_mbfs_fileio_type : &os_mbfs_textio_type);
     res->start_chunk = start_chunk;
     res->seek_chunk = start_chunk;
     res->seek_offset = file_system_chunks[start_chunk].header.name_len+2;
@@ -517,9 +512,9 @@ STATIC mp_uint_t file_read_byte(file_descriptor_obj *fd) {
     return res;
 }
 
-// Now follows the code to integrate this filesystem into the uos module.
+// Now follows the code to integrate this filesystem into the os module.
 
-mp_lexer_t *uos_mbfs_new_reader(const char *filename) {
+mp_lexer_t *os_mbfs_new_reader(const char *filename) {
     file_descriptor_obj *fd = microbit_file_open(filename, strlen(filename), false, false);
     if (fd == NULL) {
         mp_raise_OSError(MP_ENOENT);
@@ -531,7 +526,7 @@ mp_lexer_t *uos_mbfs_new_reader(const char *filename) {
     return mp_lexer_new(qstr_from_str(filename), reader);
 }
 
-mp_import_stat_t uos_mbfs_import_stat(const char *path) {
+mp_import_stat_t os_mbfs_import_stat(const char *path) {
     uint8_t chunk = microbit_find_file(path, strlen(path));
     if (chunk == FILE_NOT_FOUND) {
         return MP_IMPORT_STAT_NO_EXIST;
@@ -540,38 +535,38 @@ mp_import_stat_t uos_mbfs_import_stat(const char *path) {
     }
 }
 
-STATIC mp_obj_t uos_mbfs_file_name(mp_obj_t self) {
+STATIC mp_obj_t os_mbfs_file_name(mp_obj_t self) {
     file_descriptor_obj *fd = (file_descriptor_obj*)self;
     return microbit_file_name(fd);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(uos_mbfs_file_name_obj, uos_mbfs_file_name);
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(os_mbfs_file_name_obj, os_mbfs_file_name);
 
-STATIC mp_obj_t uos_mbfs_file_close(mp_obj_t self) {
+STATIC mp_obj_t os_mbfs_file_close(mp_obj_t self) {
     file_descriptor_obj *fd = (file_descriptor_obj*)self;
     microbit_file_close(fd);
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(uos_mbfs_file_close_obj, uos_mbfs_file_close);
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(os_mbfs_file_close_obj, os_mbfs_file_close);
 
-STATIC mp_obj_t uos_mbfs_remove(mp_obj_t name) {
+STATIC mp_obj_t os_mbfs_remove(mp_obj_t name) {
     return microbit_remove(name);
 }
-MP_DEFINE_CONST_FUN_OBJ_1(uos_mbfs_remove_obj, uos_mbfs_remove);
+MP_DEFINE_CONST_FUN_OBJ_1(os_mbfs_remove_obj, os_mbfs_remove);
 
-STATIC mp_obj_t uos_mbfs_file___exit__(size_t n_args, const mp_obj_t *args) {
+STATIC mp_obj_t os_mbfs_file___exit__(size_t n_args, const mp_obj_t *args) {
     (void)n_args;
-    return uos_mbfs_file_close(args[0]);
+    return os_mbfs_file_close(args[0]);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(uos_mbfs_file___exit___obj, 4, 4, uos_mbfs_file___exit__);
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(os_mbfs_file___exit___obj, 4, 4, os_mbfs_file___exit__);
 
 typedef struct {
     mp_obj_base_t base;
     mp_fun_1_t iternext;
     uint8_t index;
-} uos_mbfs_ilistdir_it_t;
+} os_mbfs_ilistdir_it_t;
 
-STATIC mp_obj_t uos_mbfs_ilistdir_it_iternext(mp_obj_t self_in) {
-    uos_mbfs_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
+STATIC mp_obj_t os_mbfs_ilistdir_it_iternext(mp_obj_t self_in) {
+    os_mbfs_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
 
     // Read until the next FILE_START chunk.
     for (; self->index <= chunks_in_file_system; self->index++) {
@@ -595,28 +590,27 @@ STATIC mp_obj_t uos_mbfs_ilistdir_it_iternext(mp_obj_t self_in) {
     return MP_OBJ_STOP_ITERATION;
 }
 
-STATIC mp_obj_t uos_mbfs_ilistdir(void) {
-    uos_mbfs_ilistdir_it_t *iter = m_new_obj(uos_mbfs_ilistdir_it_t);
-    iter->base.type = &mp_type_polymorph_iter;
-    iter->iternext = uos_mbfs_ilistdir_it_iternext;
+STATIC mp_obj_t os_mbfs_ilistdir(void) {
+    os_mbfs_ilistdir_it_t *iter = mp_obj_malloc(os_mbfs_ilistdir_it_t, &mp_type_polymorph_iter);
+    iter->iternext = os_mbfs_ilistdir_it_iternext;
     iter->index = 1;
 
     return MP_OBJ_FROM_PTR(iter);
 }
-MP_DEFINE_CONST_FUN_OBJ_0(uos_mbfs_ilistdir_obj, uos_mbfs_ilistdir);
+MP_DEFINE_CONST_FUN_OBJ_0(os_mbfs_ilistdir_obj, os_mbfs_ilistdir);
 
-MP_DEFINE_CONST_FUN_OBJ_0(uos_mbfs_listdir_obj, microbit_file_list);
+MP_DEFINE_CONST_FUN_OBJ_0(os_mbfs_listdir_obj, microbit_file_list);
 
 STATIC mp_obj_t microbit_file_writable(mp_obj_t self) {
     return mp_obj_new_bool(((file_descriptor_obj *)self)->writable);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(microbit_file_writable_obj, microbit_file_writable);
 
-STATIC const mp_map_elem_t uos_mbfs_file_locals_dict_table[] = {
-    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&uos_mbfs_file_close_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_name), (mp_obj_t)&uos_mbfs_file_name_obj },
+STATIC const mp_map_elem_t os_mbfs_file_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&os_mbfs_file_close_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_name), (mp_obj_t)&os_mbfs_file_name_obj },
     { MP_ROM_QSTR(MP_QSTR___enter__), (mp_obj_t)&mp_identity_obj },
-    { MP_ROM_QSTR(MP_QSTR___exit__), (mp_obj_t)&uos_mbfs_file___exit___obj },
+    { MP_ROM_QSTR(MP_QSTR___exit__), (mp_obj_t)&os_mbfs_file___exit___obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_writable), (mp_obj_t)&microbit_file_writable_obj },
     /* Stream methods */
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
@@ -624,7 +618,7 @@ STATIC const mp_map_elem_t uos_mbfs_file_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj},
 };
-STATIC MP_DEFINE_CONST_DICT(uos_mbfs_file_locals_dict, uos_mbfs_file_locals_dict_table);
+STATIC MP_DEFINE_CONST_DICT(os_mbfs_file_locals_dict, os_mbfs_file_locals_dict_table);
 
 
 STATIC const mp_stream_p_t textio_stream_p = {
@@ -634,11 +628,11 @@ STATIC const mp_stream_p_t textio_stream_p = {
 };
 
 MP_DEFINE_CONST_OBJ_TYPE(
-    uos_mbfs_textio_type,
+    os_mbfs_textio_type,
     MP_QSTR_TextIO,
     MP_TYPE_FLAG_NONE,
     protocol, &textio_stream_p,
-    locals_dict, &uos_mbfs_file_locals_dict
+    locals_dict, &os_mbfs_file_locals_dict
     );
 
 
@@ -648,15 +642,15 @@ STATIC const mp_stream_p_t fileio_stream_p = {
 };
 
 MP_DEFINE_CONST_OBJ_TYPE(
-    uos_mbfs_fileio_type,
+    os_mbfs_fileio_type,
     MP_QSTR_FileIO,
     MP_TYPE_FLAG_NONE,
     protocol, &fileio_stream_p,
-    locals_dict, &uos_mbfs_file_locals_dict
+    locals_dict, &os_mbfs_file_locals_dict
     );
 
 // From micro:bit fileobj.c
-mp_obj_t uos_mbfs_open(size_t n_args, const mp_obj_t *args) {
+mp_obj_t os_mbfs_open(size_t n_args, const mp_obj_t *args) {
     /// -1 means default; 0 explicitly false; 1 explicitly true.
     int read = -1;
     int text = -1;
@@ -690,7 +684,7 @@ mp_obj_t uos_mbfs_open(size_t n_args, const mp_obj_t *args) {
     mp_raise_ValueError(MP_ERROR_TEXT("illegal mode"));
 }
 
-STATIC mp_obj_t uos_mbfs_stat(mp_obj_t filename) {
+STATIC mp_obj_t os_mbfs_stat(mp_obj_t filename) {
     mp_obj_t file_size = microbit_file_size(filename);
 
     mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
@@ -706,6 +700,6 @@ STATIC mp_obj_t uos_mbfs_stat(mp_obj_t filename) {
     t->items[9] = MP_OBJ_NEW_SMALL_INT(0); // st_ctime
     return MP_OBJ_FROM_PTR(t);
 }
-MP_DEFINE_CONST_FUN_OBJ_1(uos_mbfs_stat_obj, uos_mbfs_stat);
+MP_DEFINE_CONST_FUN_OBJ_1(os_mbfs_stat_obj, os_mbfs_stat);
 
 #endif // MICROPY_MBFS
diff --git a/src/codal_port/modmachine.c b/src/codal_port/modmachine.c
index 447cc73..08094ad 100644
--- a/src/codal_port/modmachine.c
+++ b/src/codal_port/modmachine.c
@@ -24,12 +24,13 @@
  * THE SOFTWARE.
  */
 
-#include "py/mpconfig.h"
-#include "extmod/machine_mem.h"
-#include "extmod/machine_pulse.h"
+#include "py/runtime.h"
 #include "modmicrobit.h"
 
-#if MICROPY_PY_MACHINE
+#undef MICROPY_PY_MACHINE
+#define MICROPY_PY_MACHINE (1)
+#include "extmod/machine_mem.c"
+#undef MICROPY_PY_MACHINE
 
 // Returns a string of 8 bytes (64 bits), which is the unique ID for the MCU
 STATIC mp_obj_t machine_unique_id(void) {
@@ -37,13 +38,13 @@ STATIC mp_obj_t machine_unique_id(void) {
     mp_hal_unique_id(dev_id);
     return mp_obj_new_bytes((const void*)&dev_id, 8);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_unique_id_obj, machine_unique_id);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(microbit_unique_id_obj, machine_unique_id);
 
 // Get the MCU frequency
 STATIC mp_obj_t machine_freq(void) {
     return MP_OBJ_NEW_SMALL_INT(64000000);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_freq_obj, machine_freq);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(microbit_freq_obj, machine_freq);
 
 // Disable interrupt requests
 STATIC mp_obj_t machine_disable_irq(void) {
@@ -61,9 +62,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_enable_irq_obj, machine_enable_irq);
 
 STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_machine) },
-    { MP_ROM_QSTR(MP_QSTR_unique_id), MP_ROM_PTR(&machine_unique_id_obj) },
+    { MP_ROM_QSTR(MP_QSTR_unique_id), MP_ROM_PTR(&microbit_unique_id_obj) },
     { MP_ROM_QSTR(MP_QSTR_reset), MP_ROM_PTR(&microbit_reset_obj) },
-    { MP_ROM_QSTR(MP_QSTR_freq), MP_ROM_PTR(&machine_freq_obj) },
+    { MP_ROM_QSTR(MP_QSTR_freq), MP_ROM_PTR(&microbit_freq_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_disable_irq), MP_ROM_PTR(&machine_disable_irq_obj) },
     { MP_ROM_QSTR(MP_QSTR_enable_irq), MP_ROM_PTR(&machine_enable_irq_obj) },
@@ -82,5 +83,3 @@ const mp_obj_module_t machine_module = {
 };
 
 MP_REGISTER_MODULE(MP_QSTR_machine, machine_module);
-
-#endif // MICROPY_PY_MACHINE
diff --git a/src/codal_port/modos.c b/src/codal_port/modos.c
index 5465a2d..731a5ba 100644
--- a/src/codal_port/modos.c
+++ b/src/codal_port/modos.c
@@ -27,7 +27,7 @@
 #include "py/obj.h"
 #include "py/objtuple.h"
 #include "py/objstr.h"
-#include "ports/nrf/modules/uos/microbitfs.h"
+#include "ports/nrf/modules/os/microbitfs.h"
 
 // Include MicroPython and micro:bit version information.
 #include "genhdr/mpversion.h"
@@ -68,7 +68,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(os_uname_obj, os_uname);
 
 #if MICROPY_MBFS
 STATIC mp_obj_t os_size(mp_obj_t filename) {
-    mp_obj_tuple_t *tuple = MP_OBJ_TO_PTR(uos_mbfs_stat_obj.fun._1(filename));
+    mp_obj_tuple_t *tuple = MP_OBJ_TO_PTR(os_mbfs_stat_obj.fun._1(filename));
     return tuple->items[6];
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(os_size_obj, os_size);
@@ -80,10 +80,10 @@ STATIC const mp_rom_map_elem_t os_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_uname), MP_ROM_PTR(&os_uname_obj) },
 
     #if MICROPY_MBFS
-    { MP_ROM_QSTR(MP_QSTR_listdir), MP_ROM_PTR(&uos_mbfs_listdir_obj) },
-    { MP_ROM_QSTR(MP_QSTR_ilistdir), MP_ROM_PTR(&uos_mbfs_ilistdir_obj) },
-    { MP_ROM_QSTR(MP_QSTR_remove), MP_ROM_PTR(&uos_mbfs_remove_obj) },
-    { MP_ROM_QSTR(MP_QSTR_stat), MP_ROM_PTR(&uos_mbfs_stat_obj) },
+    { MP_ROM_QSTR(MP_QSTR_listdir), MP_ROM_PTR(&os_mbfs_listdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_ilistdir), MP_ROM_PTR(&os_mbfs_ilistdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_remove), MP_ROM_PTR(&os_mbfs_remove_obj) },
+    { MP_ROM_QSTR(MP_QSTR_stat), MP_ROM_PTR(&os_mbfs_stat_obj) },
 
     // micro:bit v1 specific
     { MP_ROM_QSTR(MP_QSTR_size), MP_ROM_PTR(&os_size_obj) },
diff --git a/src/codal_port/modradio.c b/src/codal_port/modradio.c
index 373bbde..5bd89f0 100644
--- a/src/codal_port/modradio.c
+++ b/src/codal_port/modradio.c
@@ -252,7 +252,7 @@ STATIC mp_obj_t mod_radio_receive_full(void) {
         mp_obj_t tuple[3] = {
             mp_obj_new_bytes(buf + 1, len),
             MP_OBJ_NEW_SMALL_INT(rssi),
-            MP_OBJ_NEW_SMALL_INT(timestamp_us & (MICROPY_PY_UTIME_TICKS_PERIOD - 1))
+            MP_OBJ_NEW_SMALL_INT(timestamp_us & (MICROPY_PY_TIME_TICKS_PERIOD - 1))
         };
         microbit_radio_pop();
         return mp_obj_new_tuple(3, tuple);
diff --git a/src/codal_port/modutime.c b/src/codal_port/modutime.c
deleted file mode 100644
index 5d12a26..0000000
--- a/src/codal_port/modutime.c
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * This file is part of the MicroPython project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2013-2017 Damien P. George
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "extmod/utime_mphal.h"
-
-STATIC const mp_rom_map_elem_t utime_module_globals_table[] = {
-    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_utime) },
-
-    { MP_ROM_QSTR(MP_QSTR_sleep), MP_ROM_PTR(&mp_utime_sleep_obj) },
-    { MP_ROM_QSTR(MP_QSTR_sleep_ms), MP_ROM_PTR(&mp_utime_sleep_ms_obj) },
-    { MP_ROM_QSTR(MP_QSTR_sleep_us), MP_ROM_PTR(&mp_utime_sleep_us_obj) },
-    { MP_ROM_QSTR(MP_QSTR_ticks_ms), MP_ROM_PTR(&mp_utime_ticks_ms_obj) },
-    { MP_ROM_QSTR(MP_QSTR_ticks_us), MP_ROM_PTR(&mp_utime_ticks_us_obj) },
-    { MP_ROM_QSTR(MP_QSTR_ticks_add), MP_ROM_PTR(&mp_utime_ticks_add_obj) },
-    { MP_ROM_QSTR(MP_QSTR_ticks_diff), MP_ROM_PTR(&mp_utime_ticks_diff_obj) },
-};
-
-STATIC MP_DEFINE_CONST_DICT(utime_module_globals, utime_module_globals_table);
-
-const mp_obj_module_t utime_module = {
-    .base = { &mp_type_module },
-    .globals = (mp_obj_dict_t*)&utime_module_globals,
-};
-
-MP_REGISTER_MODULE(MP_QSTR_utime, utime_module);
diff --git a/src/codal_port/mpconfigport.h b/src/codal_port/mpconfigport.h
index 2253a25..fcf2546 100644
--- a/src/codal_port/mpconfigport.h
+++ b/src/codal_port/mpconfigport.h
@@ -59,9 +59,6 @@
 #define MICROPY_FLOAT_IMPL                      (MICROPY_FLOAT_IMPL_FLOAT)
 #define MICROPY_STREAMS_NON_BLOCK               (1)
 #define MICROPY_MODULE_BUILTIN_INIT             (1)
-#define MICROPY_MODULE_WEAK_LINKS               (1)
-#define MICROPY_MODULE_FROZEN_MPY               (1)
-#define MICROPY_QSTR_EXTRA_POOL                 mp_qstr_frozen_const_pool
 #define MICROPY_USE_INTERNAL_ERRNO              (1)
 #define MICROPY_ENABLE_SCHEDULER                (1)
 
@@ -81,19 +78,18 @@
 #define MICROPY_PY_SYS_PLATFORM                 "microbit"
 
 // Extended modules
-#define MICROPY_PY_UERRNO                       (1)
-#define MICROPY_PY_UTIME_MP_HAL                 (1)
-#define MICROPY_PY_URANDOM                      (1)
-#define MICROPY_PY_URANDOM_SEED_INIT_FUNC       (rng_generate_random_word())
-#define MICROPY_PY_URANDOM_EXTRA_FUNCS          (1)
-#define MICROPY_PY_MACHINE                      (1)
+#define MICROPY_PY_ERRNO                        (1)
+#define MICROPY_PY_RANDOM                       (1)
+#define MICROPY_PY_RANDOM_SEED_INIT_FUNC        (rng_generate_random_word())
+#define MICROPY_PY_RANDOM_EXTRA_FUNCS           (1)
+#define MICROPY_PY_TIME                         (1)
 #define MICROPY_PY_MACHINE_PULSE                (1)
 
 #define MICROPY_HW_ENABLE_RNG                   (1)
 #define MICROPY_MBFS                            (1)
 
 // Custom errno list.
-#define MICROPY_PY_UERRNO_LIST \
+#define MICROPY_PY_ERRNO_LIST \
     X(EPERM) \
     X(ENOENT) \
     X(EIO) \
@@ -154,7 +150,7 @@ typedef long mp_off_t;
 // We need to provide a declaration/definition of alloca()
 #include <alloca.h>
 
-// Needed for MICROPY_PY_URANDOM_SEED_INIT_FUNC.
+// Needed for MICROPY_PY_RANDOM_SEED_INIT_FUNC.
 extern uint32_t rng_generate_random_word(void);
 
 // Needed for microbitfs.c:microbit_file_open.
diff --git a/src/codal_port/mphalport.h b/src/codal_port/mphalport.h
index 86d965a..951a8e1 100644
--- a/src/codal_port/mphalport.h
+++ b/src/codal_port/mphalport.h
@@ -28,8 +28,14 @@
 #include "microbithal.h"
 #include "nrf.h"
 
-// Not implemented and not exposed in utime module.
-#define mp_hal_ticks_cpu() (0)
+static inline mp_uint_t mp_hal_ticks_cpu(void) {
+    if (!(DWT->CTRL & DWT_CTRL_CYCCNTENA_Msk)) {
+        CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
+        DWT->CYCCNT = 0;
+        DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+    }
+    return DWT->CYCCNT;
+}
 
 void mp_hal_set_interrupt_char(int c);