diff --git a/stmhal/diskio.c b/stmhal/diskio.c
index f336b73771..fd40a6f8e7 100644
--- a/stmhal/diskio.c
+++ b/stmhal/diskio.c
@@ -113,7 +113,7 @@ DRESULT disk_read (
     }
 
     if (vfs->flags & FSUSER_NATIVE) {
-        mp_uint_t (*f)(uint8_t*, uint32_t, uint32_t) = (void*)vfs->readblocks[2];
+        mp_uint_t (*f)(uint8_t*, uint32_t, uint32_t) = (void*)(uintptr_t)vfs->readblocks[2];
         if (f(buff, sector, count) != 0) {
             return RES_ERROR;
         }
@@ -150,7 +150,7 @@ DRESULT disk_write (
     }
 
     if (vfs->flags & FSUSER_NATIVE) {
-        mp_uint_t (*f)(const uint8_t*, uint32_t, uint32_t) = (void*)vfs->writeblocks[2];
+        mp_uint_t (*f)(const uint8_t*, uint32_t, uint32_t) = (void*)(uintptr_t)vfs->writeblocks[2];
         if (f(buff, sector, count) != 0) {
             return RES_ERROR;
         }
diff --git a/stmhal/file.c b/stmhal/file.c
index 37e43a7db3..58ab934cef 100644
--- a/stmhal/file.c
+++ b/stmhal/file.c
@@ -75,7 +75,7 @@ void file_obj_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t k
 }
 
 STATIC mp_uint_t file_obj_read(mp_obj_t self_in, void *buf, mp_uint_t size, int *errcode) {
-    pyb_file_obj_t *self = self_in;
+    pyb_file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     UINT sz_out;
     FRESULT res = f_read(&self->fp, buf, size, &sz_out);
     if (res != FR_OK) {
@@ -86,7 +86,7 @@ STATIC mp_uint_t file_obj_read(mp_obj_t self_in, void *buf, mp_uint_t size, int
 }
 
 STATIC mp_uint_t file_obj_write(mp_obj_t self_in, const void *buf, mp_uint_t size, int *errcode) {
-    pyb_file_obj_t *self = self_in;
+    pyb_file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     UINT sz_out;
     FRESULT res = f_write(&self->fp, buf, size, &sz_out);
     if (res != FR_OK) {
@@ -102,29 +102,29 @@ STATIC mp_uint_t file_obj_write(mp_obj_t self_in, const void *buf, mp_uint_t siz
 }
 
 STATIC mp_obj_t file_obj_flush(mp_obj_t self_in) {
-    pyb_file_obj_t *self = self_in;
+    pyb_file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     f_sync(&self->fp);
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(file_obj_flush_obj, file_obj_flush);
 
 mp_obj_t file_obj_close(mp_obj_t self_in) {
-    pyb_file_obj_t *self = self_in;
+    pyb_file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     f_close(&self->fp);
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(file_obj_close_obj, file_obj_close);
 
-mp_obj_t file_obj___exit__(mp_uint_t n_args, const mp_obj_t *args) {
+mp_obj_t file_obj___exit__(size_t n_args, const mp_obj_t *args) {
     return file_obj_close(args[0]);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(file_obj___exit___obj, 4, 4, file_obj___exit__);
 
-STATIC mp_uint_t file_obj_ioctl(mp_obj_t o_in, mp_uint_t request, mp_uint_t arg, int *errcode) {
-    pyb_file_obj_t *self = o_in;
+STATIC mp_uint_t file_obj_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    pyb_file_obj_t *self = MP_OBJ_TO_PTR(o_in);
 
     if (request == MP_STREAM_SEEK) {
-        struct mp_stream_seek_t *s = (struct mp_stream_seek_t*)arg;
+        struct mp_stream_seek_t *s = (struct mp_stream_seek_t*)(uintptr_t)arg;
 
         switch (s->whence) {
             case 0: // SEEK_SET
@@ -156,9 +156,9 @@ STATIC mp_uint_t file_obj_ioctl(mp_obj_t o_in, mp_uint_t request, mp_uint_t arg,
 // Note: encoding is ignored for now; it's also not a valid kwarg for CPython's FileIO,
 // but by adding it here we can use one single mp_arg_t array for open() and FileIO's constructor
 STATIC const mp_arg_t file_open_args[] = {
-    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = mp_const_none} },
+    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
     { MP_QSTR_mode, MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_QSTR(MP_QSTR_r)} },
-    { MP_QSTR_encoding, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none} },
+    { MP_QSTR_encoding, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
 };
 #define FILE_OPEN_NUM_ARGS MP_ARRAY_SIZE(file_open_args)
 
@@ -209,10 +209,10 @@ STATIC mp_obj_t file_open(const mp_obj_type_t *type, mp_arg_val_t *args) {
         f_lseek(&o->fp, f_size(&o->fp));
     }
 
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 
-STATIC mp_obj_t file_obj_make_new(const mp_obj_type_t *type, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
+STATIC mp_obj_t file_obj_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_val_t arg_vals[FILE_OPEN_NUM_ARGS];
     mp_arg_parse_all_kw_array(n_args, n_kw, args, FILE_OPEN_NUM_ARGS, file_open_args, arg_vals);
     return file_open(type, arg_vals);
@@ -220,20 +220,20 @@ STATIC mp_obj_t file_obj_make_new(const mp_obj_type_t *type, mp_uint_t n_args, m
 
 // TODO gc hook to close the file if not already closed
 
-STATIC const mp_map_elem_t rawfile_locals_dict_table[] = {
-    { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), (mp_obj_t)&mp_stream_readinto_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
-    { MP_OBJ_NEW_QSTR(MP_QSTR_readlines), (mp_obj_t)&mp_stream_unbuffered_readlines_obj},
-    { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_flush), (mp_obj_t)&file_obj_flush_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&file_obj_close_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_seek), (mp_obj_t)&mp_stream_seek_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_tell), (mp_obj_t)&mp_stream_tell_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR___del__), (mp_obj_t)&file_obj_close_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR___enter__), (mp_obj_t)&mp_identity_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR___exit__), (mp_obj_t)&file_obj___exit___obj },
+STATIC const mp_rom_map_elem_t rawfile_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_read), MP_ROM_PTR(&mp_stream_read_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readall), MP_ROM_PTR(&mp_stream_readall_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&mp_stream_readinto_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readline), MP_ROM_PTR(&mp_stream_unbuffered_readline_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readlines), MP_ROM_PTR(&mp_stream_unbuffered_readlines_obj) },
+    { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&mp_stream_write_obj) },
+    { MP_ROM_QSTR(MP_QSTR_flush), MP_ROM_PTR(&file_obj_flush_obj) },
+    { MP_ROM_QSTR(MP_QSTR_close), MP_ROM_PTR(&file_obj_close_obj) },
+    { MP_ROM_QSTR(MP_QSTR_seek), MP_ROM_PTR(&mp_stream_seek_obj) },
+    { MP_ROM_QSTR(MP_QSTR_tell), MP_ROM_PTR(&mp_stream_tell_obj) },
+    { MP_ROM_QSTR(MP_QSTR___del__), MP_ROM_PTR(&file_obj_close_obj) },
+    { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&mp_identity_obj) },
+    { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&file_obj___exit___obj) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(rawfile_locals_dict, rawfile_locals_dict_table);
@@ -253,7 +253,7 @@ const mp_obj_type_t mp_type_fileio = {
     .getiter = mp_identity,
     .iternext = mp_stream_unbuffered_iter,
     .stream_p = &fileio_stream_p,
-    .locals_dict = (mp_obj_t)&rawfile_locals_dict,
+    .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
 };
 #endif
 
@@ -272,7 +272,7 @@ const mp_obj_type_t mp_type_textio = {
     .getiter = mp_identity,
     .iternext = mp_stream_unbuffered_iter,
     .stream_p = &textio_stream_p,
-    .locals_dict = (mp_obj_t)&rawfile_locals_dict,
+    .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
 };
 
 // Factory function for I/O stream classes