diff --git a/py/gc.c b/py/gc.c
index 3a3fdb00a..0d28828c0 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -1,9 +1,14 @@
 #include <stdio.h>
 #include <string.h>
+#include <stdbool.h>
 
 #include "mpconfig.h"
 #include "gc.h"
 
+#include "misc.h"
+#include "qstr.h"
+#include "obj.h"
+
 #if MICROPY_ENABLE_GC
 
 #if 0 // print debugging info
@@ -20,7 +25,9 @@ typedef unsigned char byte;
 #define STACK_SIZE (64) // tunable; minimum is 1
 
 STATIC byte *gc_alloc_table_start;
+STATIC byte *gc_mpobj_table_start;
 STATIC machine_uint_t gc_alloc_table_byte_len;
+STATIC machine_uint_t gc_mpobj_table_byte_len;
 STATIC machine_uint_t *gc_pool_start;
 STATIC machine_uint_t *gc_pool_end;
 
@@ -58,6 +65,10 @@ STATIC machine_uint_t *gc_sp;
 #define ATB_HEAD_TO_MARK(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] |= (AT_MARK << BLOCK_SHIFT(block)); } while (0)
 #define ATB_MARK_TO_HEAD(block) do { gc_alloc_table_start[(block) / BLOCKS_PER_ATB] &= (~(AT_TAIL << BLOCK_SHIFT(block))); } while (0)
 
+#define ATB_SET_MPOBJ(block) do { gc_mpobj_table_start[(block) / 8] |= (1<<(block%8)); } while (0)
+#define ATB_CLR_MPOBJ(block) do { gc_mpobj_table_start[(block) / 8] &= (~(1<<(block%8))); } while (0)
+#define ATB_IS_MPOBJ(block) ((gc_mpobj_table_start[(block) / 8]>>(block%8))&0x01)
+
 #define BLOCK_FROM_PTR(ptr) (((ptr) - (machine_uint_t)gc_pool_start) / BYTES_PER_BLOCK)
 #define PTR_FROM_BLOCK(block) (((block) * BYTES_PER_BLOCK + (machine_uint_t)gc_pool_start))
 #define ATB_FROM_BLOCK(bl) ((bl) / BLOCKS_PER_ATB)
@@ -72,7 +83,11 @@ void gc_init(void *start, void *end) {
     machine_uint_t total_word_len = (machine_uint_t*)end - (machine_uint_t*)start;
     gc_alloc_table_byte_len = total_word_len * BYTES_PER_WORD / (1 + BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
     gc_alloc_table_start = (byte*)start;
-    machine_uint_t gc_pool_block_len = gc_alloc_table_byte_len * BITS_PER_BYTE / 2;
+
+    gc_mpobj_table_byte_len = (gc_alloc_table_byte_len * BITS_PER_BYTE / 2)/8;
+    gc_mpobj_table_start = gc_alloc_table_start+gc_alloc_table_byte_len;
+
+    machine_uint_t gc_pool_block_len = (gc_alloc_table_byte_len * BITS_PER_BYTE / 2) -(gc_mpobj_table_byte_len / BYTES_PER_BLOCK);
     machine_uint_t gc_pool_word_len = gc_pool_block_len * WORDS_PER_BLOCK;
     gc_pool_start = (machine_uint_t*)end - gc_pool_word_len;
     gc_pool_end = end;
@@ -80,6 +95,9 @@ void gc_init(void *start, void *end) {
     // clear ATBs
     memset(gc_alloc_table_start, 0, gc_alloc_table_byte_len);
 
+    // clear MPOBJ flags
+    memset(gc_mpobj_table_start, 0, gc_mpobj_table_byte_len);
+
     // allocate first block because gc_pool_start points there and it will never
     // be freed, so allocating 1 block with null pointers will minimise memory loss
     ATB_FREE_TO_HEAD(0);
@@ -156,6 +174,14 @@ STATIC void gc_sweep(void) {
     for (machine_uint_t block = 0; block < gc_alloc_table_byte_len * BLOCKS_PER_ATB; block++) {
         switch (ATB_GET_KIND(block)) {
             case AT_HEAD:
+                if (ATB_IS_MPOBJ(block)) {
+                    ATB_CLR_MPOBJ(block); // clear mpobj flag
+                    mp_obj_t *self = (mp_obj_t*)PTR_FROM_BLOCK(block);
+                    mp_obj_type_t *type= mp_obj_get_type(self);
+                    if (type->del != NULL) {
+                        type->del(self);
+                    }
+                }
                 free_tail = 1;
                 // fall through to free the head
 
@@ -236,7 +262,7 @@ void gc_info(gc_info_t *info) {
     info->free *= BYTES_PER_BLOCK;
 }
 
-void *gc_alloc(machine_uint_t n_bytes) {
+void *_gc_alloc(machine_uint_t n_bytes, bool is_mpobj) {
     machine_uint_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
     DEBUG_printf("gc_alloc(" UINT_FMT " bytes -> " UINT_FMT " blocks)\n", n_bytes, n_blocks);
 
@@ -279,6 +305,10 @@ found:
     // mark first block as used head
     ATB_FREE_TO_HEAD(start_block);
 
+    if (is_mpobj) {
+        ATB_SET_MPOBJ(start_block);
+    }
+
     // mark rest of blocks as used tail
     // TODO for a run of many blocks can make this more efficient
     for (machine_uint_t bl = start_block + 1; bl <= end_block; bl++) {
@@ -289,6 +319,14 @@ found:
     return (void*)(gc_pool_start + start_block * WORDS_PER_BLOCK);
 }
 
+void *gc_alloc(machine_uint_t n_bytes) {
+    return _gc_alloc(n_bytes, false);
+}
+
+void *gc_alloc_mp_obj(machine_uint_t n_bytes) {
+    return _gc_alloc(n_bytes, true);
+}
+
 // force the freeing of a piece of memory
 void gc_free(void *ptr_in) {
     machine_uint_t ptr = (machine_uint_t)ptr_in;
diff --git a/py/gc.h b/py/gc.h
index c8a1a996c..f8aeb393a 100644
--- a/py/gc.h
+++ b/py/gc.h
@@ -4,6 +4,7 @@ void gc_collect_root(void **ptrs, machine_uint_t len);
 void gc_collect_end(void);
 void gc_collect(void);
 void *gc_alloc(machine_uint_t n_bytes);
+void *gc_alloc_mp_obj(machine_uint_t n_bytes);
 void gc_free(void *ptr);
 machine_uint_t gc_nbytes(void *ptr);
 void *gc_realloc(void *ptr, machine_uint_t n_bytes);
diff --git a/py/malloc.c b/py/malloc.c
index 27eaac108..b0094a254 100644
--- a/py/malloc.c
+++ b/py/malloc.c
@@ -31,6 +31,7 @@ STATIC int peak_bytes_allocated = 0;
 #undef free
 #undef realloc
 #define malloc gc_alloc
+#define malloc_mp_obj gc_alloc_mp_obj
 #define free gc_free
 #define realloc gc_realloc
 #endif // MICROPY_ENABLE_GC
@@ -53,6 +54,24 @@ void *m_malloc(int num_bytes) {
     return ptr;
 }
 
+void *m_malloc_mp_obj(int num_bytes) {
+    if (num_bytes == 0) {
+        return NULL;
+    }
+    void *ptr = malloc_mp_obj(num_bytes);
+    if (ptr == NULL) {
+        printf("could not allocate memory, allocating %d bytes\n", num_bytes);
+        return NULL;
+    }
+#if MICROPY_MEM_STATS
+    total_bytes_allocated += num_bytes;
+    current_bytes_allocated += num_bytes;
+    UPDATE_PEAK();
+#endif
+    DEBUG_printf("malloc %d : %p\n", num_bytes, ptr);
+    return ptr;
+}
+
 void *m_malloc0(int num_bytes) {
     void *ptr = m_malloc(num_bytes);
     if (ptr != NULL) {
diff --git a/py/misc.h b/py/misc.h
index 35081f18e..c99f819c6 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -27,12 +27,14 @@ typedef unsigned int uint;
 #define m_new0(type, num) ((type*)(m_malloc0(sizeof(type) * (num))))
 #define m_new_obj(type) (m_new(type, 1))
 #define m_new_obj_var(obj_type, var_type, var_num) ((obj_type*)m_malloc(sizeof(obj_type) + sizeof(var_type) * (var_num)))
+#define m_new_mp_obj(type)((type*)(m_malloc_mp_obj(sizeof(type))))
 #define m_renew(type, ptr, old_num, new_num) ((type*)(m_realloc((ptr), sizeof(type) * (old_num), sizeof(type) * (new_num))))
 #define m_del(type, ptr, num) m_free(ptr, sizeof(type) * (num))
 #define m_del_obj(type, ptr) (m_del(type, ptr, 1))
 #define m_del_var(obj_type, var_type, var_num, ptr) (m_free(ptr, sizeof(obj_type) + sizeof(var_type) * (var_num)))
 
 void *m_malloc(int num_bytes);
+void *m_malloc_mp_obj(int num_bytes);
 void *m_malloc0(int num_bytes);
 void *m_realloc(void *ptr, int old_num_bytes, int new_num_bytes);
 void m_free(void *ptr, int num_bytes);
diff --git a/py/obj.h b/py/obj.h
index 952187e46..4178295be 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -154,6 +154,7 @@ typedef mp_obj_t (*mp_binary_op_fun_t)(int op, mp_obj_t, mp_obj_t);
 typedef void (*mp_load_attr_fun_t)(mp_obj_t self_in, qstr attr, mp_obj_t *dest); // for fail, do nothing; for attr, dest[0] = value; for method, dest[0] = method, dest[1] = self
 typedef bool (*mp_store_attr_fun_t)(mp_obj_t self_in, qstr attr, mp_obj_t value); // return true if store succeeded
 typedef bool (*mp_store_item_fun_t)(mp_obj_t self_in, mp_obj_t index, mp_obj_t value); // return true if store succeeded
+typedef void (*mp_del_fun_t)(mp_obj_t self_in);
 
 typedef struct _mp_method_t {
     qstr name;
@@ -236,6 +237,7 @@ struct _mp_obj_type_t {
 
     unpack seq      list tuple
     */
+    mp_del_fun_t del;
 };
 
 typedef struct _mp_obj_type_t mp_obj_type_t;
diff --git a/stm/file.c b/stm/file.c
index 40ac3ff9c..fc6abfcd6 100644
--- a/stm/file.c
+++ b/stm/file.c
@@ -13,6 +13,12 @@ typedef struct _pyb_file_obj_t {
     FIL fp;
 } pyb_file_obj_t;
 
+void file_obj_del(mp_obj_t self_in) {
+    pyb_file_obj_t *self = self_in;
+    f_close(&self->fp);
+    printf("<file del called>\n");
+}
+
 void file_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
     printf("<file %p>", self_in);
 }
@@ -64,13 +70,14 @@ static const mp_obj_type_t file_obj_type = {
     { &mp_type_type },
     .name = MP_QSTR_File,
     .print = file_obj_print,
+    .del   = file_obj_del,
     .locals_dict = (mp_obj_t)&file_locals_dict,
 };
 
 mp_obj_t pyb_io_open(mp_obj_t o_filename, mp_obj_t o_mode) {
     const char *filename = mp_obj_str_get_str(o_filename);
     const char *mode = mp_obj_str_get_str(o_mode);
-    pyb_file_obj_t *self = m_new_obj(pyb_file_obj_t);
+    pyb_file_obj_t *self = m_new_mp_obj(pyb_file_obj_t);
     self->base.type = &file_obj_type;
     if (mode[0] == 'r') {
         // open for reading