diff --git a/nrf5/Makefile b/nrf5/Makefile
index c72d089867..dcac81dcdd 100644
--- a/nrf5/Makefile
+++ b/nrf5/Makefile
@@ -37,7 +37,7 @@ endif
 # qstr definitions (must come before including py.mk)
 QSTR_DEFS = qstrdefsport.h $(BUILD)/pins_qstr.h
 
-FROZEN_MPY_DIR = modules
+FROZEN_DIR = modules
 
 # include py core make definitions
 include ../py/py.mk
@@ -78,8 +78,6 @@ CFLAGS += $(INC) -Wall -Werror -ansi -std=gnu99 -nostdlib $(COPT) $(NRF_DEFINES)
 CFLAGS += -fno-strict-aliasing
 CFLAGS += -Iboards/$(BOARD)
 CFLAGS += -DNRF5_HAL_H='<$(MCU_VARIANT)_hal.h>'
-CFLAGS += -DMICROPY_QSTR_EXTRA_POOL=mp_qstr_frozen_const_pool
-CFLAGS += -DMICROPY_MODULE_FROZEN_MPY
 
 LDFLAGS = $(CFLAGS)
 LDFLAGS += -Xlinker -Map=$(@:.elf=.map)
@@ -101,7 +99,6 @@ SRC_LIB = $(addprefix lib/,\
 	libc/string0.c \
 	mp-readline/readline.c \
 	utils/pyexec.c \
-	utils/pyhelp.c \
 	timeutils/timeutils.c \
 	fatfs/ff.c \
 	fatfs/option/ccsbcs.c \
@@ -146,7 +143,6 @@ SRC_C += \
 	moduos.c \
 	fatfs_port.c \
 	builtin_open.c \
-	lexerfatfs.c \
 	modusocket.c \
 	modnetwork.c \
 	timer.c \
@@ -187,8 +183,6 @@ OBJ += $(addprefix $(BUILD)/, $(SRC_LIB:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_HAL:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(DRIVERS_SRC_C:.c=.o))
 OBJ += $(BUILD)/pins_gen.o
-OBJ += $(BUILD)/$(BUILD)/frozen_mpy.o
-
 
 $(BUILD)/$(FATFS_DIR)/ff.o: COPT += -Os
 $(filter $(PY_BUILD)/../extmod/vfs_fat_%.o, $(PY_O)): COPT += -Os
@@ -256,16 +250,18 @@ GEN_PINS_QSTR = $(BUILD)/pins_qstr.h
 GEN_PINS_AF_CONST = $(HEADER_BUILD)/pins_af_const.h
 GEN_PINS_AF_PY = $(BUILD)/pins_af.py
 
-# to build .mpy files from .py files
-$(BUILD)/$(FROZEN_MPY_DIR)/%.mpy: $(FROZEN_MPY_DIR)/%.py
-	@$(ECHO) "MPY $<"
-	$(Q)$(MKDIR) -p $(dir $@)
-	$(Q)$(MPY_CROSS) -o $@ -s $(^:$(FROZEN_MPY_DIR)/%=%) $^
+ifneq ($(FROZEN_DIR),)
+# To use frozen source modules, put your .py files in a subdirectory (eg scripts/)
+# and then invoke make with FROZEN_DIR=scripts (be sure to build from scratch).
+CFLAGS += -DMICROPY_MODULE_FROZEN_STR
+endif
 
-# to build frozen_mpy.c from all .mpy files
-$(BUILD)/frozen_mpy.c: $(FROZEN_MPY_MPY_FILES) $(BUILD)/genhdr/qstrdefs.generated.h
-	@$(ECHO) "Creating $@"
-	$(Q)$(PYTHON) $(MPY_TOOL) -f -q $(BUILD)/genhdr/qstrdefs.preprocessed.h -mlongint-impl mpz $(FROZEN_MPY_MPY_FILES) > $@
+ifneq ($(FROZEN_MPY_DIR),)
+# To use frozen bytecode, put your .py files in a subdirectory (eg frozen/) and
+# then invoke make with FROZEN_MPY_DIR=frozen (be sure to build from scratch).
+CFLAGS += -DMICROPY_QSTR_EXTRA_POOL=mp_qstr_frozen_const_pool
+CFLAGS += -DMICROPY_MODULE_FROZEN_MPY
+endif
 
 include ../py/mkrules.mk
 include mkrules.mk
diff --git a/nrf5/boards/microbit/mpconfigboard.h b/nrf5/boards/microbit/mpconfigboard.h
index ed655896ea..7de7f4ac95 100644
--- a/nrf5/boards/microbit/mpconfigboard.h
+++ b/nrf5/boards/microbit/mpconfigboard.h
@@ -30,7 +30,7 @@
 #define MICROPY_HW_MCU_NAME         "NRF51822"
 #define MICROPY_PY_SYS_PLATFORM     "nrf51"
 
-#define MICROPY_PY_MACHINE_SPI      (0)
+#define MICROPY_PY_MACHINE_HW_SPI   (0)
 #define MICROPY_PY_MACHINE_PWM      (0)
 #define MICROPY_PY_MACHINE_TIMER    (0)
 #define MICROPY_PY_MACHINE_RTC      (0)
diff --git a/nrf5/boards/pca10000/mpconfigboard.h b/nrf5/boards/pca10000/mpconfigboard.h
index e38ae686c1..01840d26e8 100644
--- a/nrf5/boards/pca10000/mpconfigboard.h
+++ b/nrf5/boards/pca10000/mpconfigboard.h
@@ -30,7 +30,7 @@
 #define MICROPY_HW_MCU_NAME         "NRF51822"
 #define MICROPY_PY_SYS_PLATFORM     "nrf51-dongle"
 
-#define MICROPY_PY_MACHINE_SPI      (0)
+#define MICROPY_PY_MACHINE_HW_SPI   (0)
 #define MICROPY_PY_MACHINE_PWM      (0)
 
 #define MICROPY_HW_HAS_SWITCH       (0)
diff --git a/nrf5/boards/pca10001/mpconfigboard.h b/nrf5/boards/pca10001/mpconfigboard.h
index b440b7f900..06570af7c4 100644
--- a/nrf5/boards/pca10001/mpconfigboard.h
+++ b/nrf5/boards/pca10001/mpconfigboard.h
@@ -30,7 +30,7 @@
 #define MICROPY_HW_MCU_NAME         "NRF51822"
 #define MICROPY_PY_SYS_PLATFORM     "nrf51-DK"
 
-#define MICROPY_PY_MACHINE_SPI      (0)
+#define MICROPY_PY_MACHINE_HW_SPI   (0)
 #define MICROPY_PY_MACHINE_PWM      (0)
 
 #define MICROPY_HW_HAS_SWITCH       (0)
diff --git a/nrf5/boards/pca10028/mpconfigboard.h b/nrf5/boards/pca10028/mpconfigboard.h
index c4eab19cf1..1b558b3b7f 100644
--- a/nrf5/boards/pca10028/mpconfigboard.h
+++ b/nrf5/boards/pca10028/mpconfigboard.h
@@ -36,7 +36,7 @@
 #define MICROPY_PY_DISPLAY_OLED_SSD1305     (1)
 #define MICROPY_PY_DISPLAY_OLED_SSD1306     (0)
 
-#define MICROPY_PY_MACHINE_SPI      (1)
+#define MICROPY_PY_MACHINE_HW_SPI   (1)
 #define MICROPY_PY_MACHINE_PWM      (0)
 #define MICROPY_PY_MACHINE_TIMER    (1)
 #define MICROPY_PY_MACHINE_RTC      (1)
diff --git a/nrf5/boards/pca10040/mpconfigboard.h b/nrf5/boards/pca10040/mpconfigboard.h
index e5d0106087..58e7aaff1a 100644
--- a/nrf5/boards/pca10040/mpconfigboard.h
+++ b/nrf5/boards/pca10040/mpconfigboard.h
@@ -31,7 +31,7 @@
 #define MICROPY_PY_SYS_PLATFORM     "nrf52-DK"
 
 #define MICROPY_PY_MACHINE_PWM      (1)
-#define MICROPY_PY_MACHINE_SPI      (1)
+#define MICROPY_PY_MACHINE_HW_SPI   (1)
 #define MICROPY_PY_MACHINE_TIMER    (1)
 #define MICROPY_PY_MACHINE_RTC      (1)
 #define MICROPY_PY_MACHINE_HW_I2C   (1)
diff --git a/nrf5/boards/pca10056/mpconfigboard.h b/nrf5/boards/pca10056/mpconfigboard.h
index 91f7e00bc8..cf711ae1bb 100644
--- a/nrf5/boards/pca10056/mpconfigboard.h
+++ b/nrf5/boards/pca10056/mpconfigboard.h
@@ -31,7 +31,7 @@
 #define MICROPY_PY_SYS_PLATFORM     "nrf52840-PDK"
 
 #define MICROPY_PY_MACHINE_PWM      (1)
-#define MICROPY_PY_MACHINE_SPI      (1)
+#define MICROPY_PY_MACHINE_HW_SPI   (1)
 #define MICROPY_PY_MACHINE_HW_I2C   (1)
 #define MICROPY_PY_MACHINE_ADC      (1)
 
diff --git a/nrf5/help.c b/nrf5/help.c
index a3a12bd19c..f17439a19d 100644
--- a/nrf5/help.c
+++ b/nrf5/help.c
@@ -25,16 +25,13 @@
  * THE SOFTWARE.
  */
 
-#include <stdio.h>
-
-#include "lib/utils/pyhelp.h"
-#include "mpconfigboard.h"
+#include "py/builtin.h"
 
 #if BLUETOOTH_SD
 #include "help_sd.h"
 #endif
 
-STATIC const char help_text[] =
+const char * nrf5_help_text =
 "Welcome to MicroPython!\n"
 "\n"
 "For online help please visit http://micropython.org/help/.\n"
@@ -51,17 +48,3 @@ HELP_TEXT_SD
 "\n"
 "For further help on a specific object, type help(obj)\n"
 ;
-
-STATIC mp_obj_t pyb_help(uint n_args, const mp_obj_t *args) {
-    if (n_args == 0) {
-        // print a general help message
-        printf("%s", help_text);
-
-    } else {
-        // try to print something sensible about the given object
-        pyhelp_print_obj(args[0]);
-    }
-
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_help_obj, 0, 1, pyb_help);
diff --git a/nrf5/lexerfatfs.c b/nrf5/lexerfatfs.c
deleted file mode 100644
index fd7f62dfdd..0000000000
--- a/nrf5/lexerfatfs.c
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * This file is part of the MicroPython project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2013, 2014 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 "py/lexer.h"
-
-mp_lexer_t *fat_vfs_lexer_new_from_file(const char *filename);
-
-// TODO: Instead of such shims, probably better to let port #define
-// mp_lexer_new_from_file to a function it wants to use.
-mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
-    return fat_vfs_lexer_new_from_file(filename);
-}
diff --git a/nrf5/mpconfigport.h b/nrf5/mpconfigport.h
index cb1922cdac..aafcd3812c 100644
--- a/nrf5/mpconfigport.h
+++ b/nrf5/mpconfigport.h
@@ -50,6 +50,7 @@
 #define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (0)
 #define MICROPY_OPT_MPZ_BITWISE     (0)
+#define MICROPY_READER_FATFS        (1)
 
 // fatfs configuration used in ffconf.h
 #define MICROPY_FATFS_ENABLE_LFN       (1)
@@ -73,6 +74,9 @@
 #define MICROPY_PY_BUILTINS_FROZENSET (1)
 #define MICROPY_PY_BUILTINS_EXECFILE (0)
 #define MICROPY_PY_BUILTINS_COMPILE (1)
+#define MICROPY_PY_BUILTINS_HELP    (1)
+#define MICROPY_PY_BUILTINS_HELP_TEXT nrf5_help_text
+#define MICROPY_PY_BUILTINS_HELP_MODULES (1)
 #define MICROPY_PY_ALL_SPECIAL_METHODS (0)
 #define MICROPY_PY_MICROPYTHON_MEM_INFO (1)
 #define MICROPY_PY_ARRAY_SLICE_ASSIGN (0)
@@ -100,7 +104,7 @@
 #define MICROPY_PY_MACHINE          (1)
 #define MICROPY_PY_MACHINE_PULSE    (0)
 #define MICROPY_PY_MACHINE_I2C      (0)
-
+#define MICROPY_PY_MACHINE_SPI      (0)
 #define MICROPY_PY_MACHINE_SPI_MIN_DELAY (0)
 #define MICROPY_PY_FRAMEBUF         (0)
 
@@ -112,8 +116,8 @@
 #define MICROPY_PY_MACHINE_HW_I2C   (0)
 #endif
 
-#ifndef MICROPY_PY_MACHINE_SPI
-#define MICROPY_PY_MACHINE_SPI      (1)
+#ifndef MICROPY_PY_MACHINE_HW_SPI
+#define MICROPY_PY_MACHINE_HW_SPI   (1)
 #endif
 
 #ifndef MICROPY_PY_MACHINE_PWM
diff --git a/nrf5/spi.c b/nrf5/spi.c
index a9a31337d2..7e3d831e88 100644
--- a/nrf5/spi.c
+++ b/nrf5/spi.c
@@ -37,7 +37,7 @@
 #include "spi.h"
 #include "hal_spi.h"
 
-#if MICROPY_PY_MACHINE_SPI
+#if MICROPY_PY_MACHINE_HW_SPI
 
 /// \moduleref pyb
 /// \class SPI - a master-driven serial protocol
@@ -113,7 +113,7 @@ void spi_init(SPI_HandleTypeDef *spi, bool enable_nss_pin) {
 void spi_deinit(SPI_HandleTypeDef *spi) {
 }
 
-STATIC void spi_transfer(const pyb_spi_obj_t * self, size_t len, const uint8_t * src, uint8_t * dest, uint32_t timeout) {
+STATIC void spi_transfer(const pyb_spi_obj_t * self, size_t len, const void * src, void * dest) {
 	hal_spi_master_tx_rx(self->spi->instance, len, src, dest);
 }
 
@@ -296,9 +296,50 @@ STATIC void machine_hard_spi_deinit(mp_obj_t self_in) {
 
 STATIC void machine_hard_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
     machine_hard_spi_obj_t *self = (machine_hard_spi_obj_t*)self_in;
-    spi_transfer(self->pyb, len, src, dest, 100);
+    spi_transfer(self->pyb, len, src, dest);
 }
 
+
+STATIC mp_obj_t mp_machine_spi_read(size_t n_args, const mp_obj_t *args) {
+    vstr_t vstr;
+    vstr_init_len(&vstr, mp_obj_get_int(args[1]));
+    memset(vstr.buf, n_args == 3 ? mp_obj_get_int(args[2]) : 0, vstr.len);
+    spi_transfer(args[0], vstr.len, vstr.buf, vstr.buf);
+    return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_read_obj, 2, 3, mp_machine_spi_read);
+
+STATIC mp_obj_t mp_machine_spi_readinto(size_t n_args, const mp_obj_t *args) {
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
+    memset(bufinfo.buf, n_args == 3 ? mp_obj_get_int(args[2]) : 0, bufinfo.len);
+    spi_transfer(args[0], bufinfo.len, bufinfo.buf, bufinfo.buf);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_readinto_obj, 2, 3, mp_machine_spi_readinto);
+
+STATIC mp_obj_t mp_machine_spi_write(mp_obj_t self, mp_obj_t wr_buf) {
+    mp_buffer_info_t src;
+    mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
+    spi_transfer(self, src.len, (const uint8_t*)src.buf, NULL);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(mp_machine_spi_write_obj, mp_machine_spi_write);
+
+STATIC mp_obj_t mp_machine_spi_write_readinto(mp_obj_t self, mp_obj_t wr_buf, mp_obj_t rd_buf) {
+    mp_buffer_info_t src;
+    mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
+    mp_buffer_info_t dest;
+    mp_get_buffer_raise(rd_buf, &dest, MP_BUFFER_WRITE);
+    if (src.len != dest.len) {
+        mp_raise_ValueError("buffers must be the same length");
+    }
+    spi_transfer(self, src.len, src.buf, dest.buf);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(mp_machine_spi_write_readinto_obj, mp_machine_spi_write_readinto);
+
+
 STATIC const mp_machine_spi_p_t machine_hard_spi_p = {
     .transfer = machine_hard_spi_transfer,
 };
@@ -312,4 +353,4 @@ const mp_obj_type_t machine_hard_spi_type = {
     .locals_dict = (mp_obj_t)&machine_spi_locals_dict,
 };
 
-#endif // MICROPY_PY_MACHINE_SPI
+#endif // MICROPY_PY_MACHINE_HW_SPI
diff --git a/nrf5/uart.c b/nrf5/uart.c
index 4edaea3881..a510c834a9 100644
--- a/nrf5/uart.c
+++ b/nrf5/uart.c
@@ -348,8 +348,6 @@ STATIC const mp_map_elem_t pyb_uart_locals_dict_table[] = {
 
     /// \method read([nbytes])
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
-    /// \method readall()
-    { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
     /// \method readline()
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     /// \method readinto(buf[, nbytes])