diff --git a/py/binary.c b/py/binary.c
index d3dd00954615ba89cc9ea4fe7d614af67938aac9..ee95d56e44a8c75cc4956e3fa9e2f7bb06daed4b 100644
--- a/py/binary.c
+++ b/py/binary.c
@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include <stdlib.h>
 #include <assert.h>
 
 #include "misc.h"
@@ -9,34 +10,52 @@
 
 // Helpers to work with binary-encoded data
 
-int mp_binary_get_size(char typecode) {
-    // This assumes that unsigned and signed types are of the same type,
-    // which is invariant for [u]intN_t.
-    switch (typecode) {
-        case BYTEARRAY_TYPECODE:
-        case 'b':
-        case 'B':
-            return sizeof(int8_t);
-        case 'h':
-        case 'H':
-            return sizeof(int16_t);
-        case 'i':
-        case 'I':
-            return sizeof(int32_t);
-        case 'l':
-        case 'L':
-            return sizeof(int32_t);
-        case 'q':
-        case 'Q':
-            return sizeof(long long);
-#if MICROPY_ENABLE_FLOAT
-        case 'f':
-            return sizeof(float);
-        case 'd':
-            return sizeof(double);
-#endif
+int mp_binary_get_size(char struct_type, char val_type, uint *palign) {
+    int size = 0;
+    int align = 1;
+    switch (struct_type) {
+        case '<': case '>':
+            switch (val_type) {
+                case 'b': case 'B':
+                    size = 1; break;
+                case 'h': case 'H':
+                    size = 2; break;
+                case 'i': case 'I':
+                    size = 4; break;
+                case 'l': case 'L':
+                    size = 4; break;
+                case 'q': case 'Q':
+                    size = 8; break;
+            }
+            break;
+        case '@': {
+            // TODO:
+            // The simplest heuristic for alignment is to align by value
+            // size, but that doesn't work for "bigger than int" types,
+            // for example, long long may very well have long alignment
+            // So, we introduce separate alignment handling, but having
+            // formal support for that is different from actually supporting
+            // particular (or any) ABI.
+            switch (val_type) {
+                case BYTEARRAY_TYPECODE:
+                case 'b': case 'B':
+                    align = size = 1; break;
+                case 'h': case 'H':
+                    align = size = sizeof(short); break;
+                case 'i': case 'I':
+                    align = size = sizeof(int); break;
+                case 'l': case 'L':
+                    align = size = sizeof(long); break;
+                case 'q': case 'Q':
+                    // TODO: This is for x86
+                    align = sizeof(int); size = sizeof(long long); break;
+            }
+        }
     }
-    return -1;
+    if (palign != NULL) {
+        *palign = align;
+    }
+    return size;
 }
 
 mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index) {
@@ -80,48 +99,17 @@ mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index) {
 #define is_signed(typecode) (typecode > 'Z')
 mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr) {
     byte *p = *ptr;
-    uint size = 0;
-    switch (struct_type) {
-        case '<': case '>':
-            switch (val_type) {
-                case 'b': case 'B':
-                    size = 1; break;
-                case 'h': case 'H':
-                    size = 2; break;
-                case 'i': case 'I':
-                    size = 4; break;
-                case 'l': case 'L':
-                    size = 4; break;
-            }
-            break;
-        case '@': {
-            // TODO:
-            // The simplest heuristic for alignment is to align by value
-            // size, but that doesn't work for "bigger than int" types,
-            // for example, long long may very well have long alignment
-            // So, we introduce separate alignment handling, but having
-            // formal support for that is different from actually supporting
-            // particular (or any) ABI.
-            uint align = 0;
-            switch (val_type) {
-                case 'b': case 'B':
-                    align = size = 1; break;
-                case 'h': case 'H':
-                    align = size = sizeof(short); break;
-                case 'i': case 'I':
-                    align = size = sizeof(int); break;
-                case 'l': case 'L':
-                    align = size = sizeof(long); break;
-            }
-            // Make pointer aligned
-            p = (byte*)(((machine_uint_t)p + align - 1) & ~(align - 1));
-            #if MP_ENDIANNESS_LITTLE
-            struct_type = '<';
-            #else
-            struct_type = '>';
-            #endif
-            break;
-        }
+    uint align;
+
+    int size = mp_binary_get_size(struct_type, val_type, &align);
+    if (struct_type == '@') {
+        // Make pointer aligned
+        p = (byte*)(((machine_uint_t)p + align - 1) & ~(align - 1));
+        #if MP_ENDIANNESS_LITTLE
+        struct_type = '<';
+        #else
+        struct_type = '>';
+        #endif
     }
 
     int delta;
@@ -150,6 +138,45 @@ mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr) {
     }
 }
 
+void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **ptr) {
+    byte *p = *ptr;
+    uint align;
+
+    int size = mp_binary_get_size(struct_type, val_type, &align);
+    if (struct_type == '@') {
+        // Make pointer aligned
+        p = (byte*)(((machine_uint_t)p + align - 1) & ~(align - 1));
+        #if MP_ENDIANNESS_LITTLE
+        struct_type = '<';
+        #else
+        struct_type = '>';
+        #endif
+    }
+
+#if MP_ENDIANNESS_BIG
+#error Not implemented
+#endif
+    machine_int_t val = mp_obj_int_get_checked(val_in);
+    byte *in = (byte*)&val;
+    int in_delta, out_delta;
+    uint val_sz = MIN(size, sizeof(val));
+    if (struct_type == '>') {
+        in_delta = -1;
+        out_delta = 1;
+        in += val_sz - 1;
+    } else {
+        in_delta = out_delta = 1;
+    }
+
+    for (uint i = val_sz; i > 0; i--) {
+        *p = *in;
+        p += out_delta;
+        in += in_delta;
+    }
+
+    *ptr += size;
+}
+
 void mp_binary_set_val_array(char typecode, void *p, int index, mp_obj_t val_in) {
     switch (typecode) {
 #if MICROPY_ENABLE_FLOAT
diff --git a/py/binary.h b/py/binary.h
index 538d6e7f296c5cb02d741f985389f0b4c0989115..46fb5b36b9f3bd5176fb807b7c220a4033cbae36 100644
--- a/py/binary.h
+++ b/py/binary.h
@@ -2,8 +2,9 @@
 // (underlyingly they're same).
 #define BYTEARRAY_TYPECODE 0
 
-int mp_binary_get_size(char typecode);
+int mp_binary_get_size(char struct_type, char val_type, uint *palign);
 mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index);
-mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr);
 void mp_binary_set_val_array(char typecode, void *p, int index, mp_obj_t val_in);
 void mp_binary_set_val_array_from_int(char typecode, void *p, int index, machine_int_t val);
+mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr);
+void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **ptr);
diff --git a/py/modstruct.c b/py/modstruct.c
index cd2516b240ec2081a779573ac609741bcde4365b..81afd94d169234238dd72d1fbf215c169baa54f2 100644
--- a/py/modstruct.c
+++ b/py/modstruct.c
@@ -6,6 +6,7 @@
 #include "obj.h"
 #include "builtin.h"
 #include "objtuple.h"
+#include "objstr.h"
 #include "binary.h"
 
 #if MICROPY_ENABLE_MOD_STRUCT
@@ -37,12 +38,14 @@ STATIC uint calcsize_items(const char *fmt) {
 STATIC mp_obj_t struct_calcsize(mp_obj_t fmt_in) {
     const char *fmt = mp_obj_str_get_str(fmt_in);
     char fmt_type = get_fmt_type(&fmt);
-    (void)fmt_type;
     machine_uint_t size;
     for (size = 0; *fmt; fmt++) {
-        int sz = mp_binary_get_size(*fmt);
+        uint align;
+        int sz = mp_binary_get_size(fmt_type, *fmt, &align);
         // TODO
         assert(sz != -1);
+        // Apply alignment
+        size = (size + align - 1) & ~(align - 1);
         size += sz;
     }
     return MP_OBJ_NEW_SMALL_INT(size);
@@ -67,9 +70,26 @@ STATIC mp_obj_t struct_unpack(mp_obj_t fmt_in, mp_obj_t data_in) {
 }
 MP_DEFINE_CONST_FUN_OBJ_2(struct_unpack_obj, struct_unpack);
 
+STATIC mp_obj_t struct_pack(uint n_args, mp_obj_t *args) {
+    // TODO: "The arguments must match the values required by the format exactly."
+    const char *fmt = mp_obj_str_get_str(args[0]);
+    char fmt_type = get_fmt_type(&fmt);
+    int size = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
+    byte *p;
+    mp_obj_t res = mp_obj_str_builder_start(&mp_type_bytes, size, &p);
+    memset(p, 0, size);
+
+    for (uint i = 1; i < n_args; i++) {
+        mp_binary_set_val(fmt_type, *fmt++, args[i], &p);
+    }
+    return res;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(struct_pack_obj, 1, -1, struct_pack);
+
 STATIC const mp_map_elem_t mp_module_struct_globals_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_struct) },
     { MP_OBJ_NEW_QSTR(MP_QSTR_calcsize), (mp_obj_t)&struct_calcsize_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_pack), (mp_obj_t)&struct_pack_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_unpack), (mp_obj_t)&struct_unpack_obj },
 };
 
diff --git a/py/obj.h b/py/obj.h
index dd25ec4f227d2b7c79c5f00492210119ddfeb38c..44d9bf6a6dfeb069bd11cc6da6b7d9d3b7b8d1bf 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -418,7 +418,7 @@ machine_int_t mp_obj_int_get(mp_obj_t self_in);
 #if MICROPY_ENABLE_FLOAT
 mp_float_t mp_obj_int_as_float(mp_obj_t self_in);
 #endif
-// Will rains exception if value doesn't fit into machine_int_t
+// Will raise exception if value doesn't fit into machine_int_t
 machine_int_t mp_obj_int_get_checked(mp_obj_t self_in);
 
 // exception
diff --git a/py/objarray.c b/py/objarray.c
index c6da45728ad165f3eccad82fbd0f07bde4aba69d..2255e29d7be4977b403b4cdb291517c30cb2ed37 100644
--- a/py/objarray.c
+++ b/py/objarray.c
@@ -121,7 +121,7 @@ STATIC mp_obj_t array_append(mp_obj_t self_in, mp_obj_t arg) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_array) || MP_OBJ_IS_TYPE(self_in, &mp_type_bytearray));
     mp_obj_array_t *self = self_in;
     if (self->free == 0) {
-        int item_sz = mp_binary_get_size(self->typecode);
+        int item_sz = mp_binary_get_size('@', self->typecode, NULL);
         // TODO: alloc policy
         self->free = 8;
         self->items = m_realloc(self->items,  item_sz * self->len, item_sz * (self->len + self->free));
@@ -154,7 +154,7 @@ STATIC mp_obj_t array_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t value
 STATIC machine_int_t array_get_buffer(mp_obj_t o_in, mp_buffer_info_t *bufinfo, int flags) {
     mp_obj_array_t *o = o_in;
     bufinfo->buf = o->items;
-    bufinfo->len = o->len * mp_binary_get_size(o->typecode);
+    bufinfo->len = o->len * mp_binary_get_size('@', o->typecode, NULL);
     bufinfo->typecode = o->typecode;
     return 0;
 }
@@ -190,7 +190,7 @@ const mp_obj_type_t mp_type_bytearray = {
 };
 
 STATIC mp_obj_array_t *array_new(char typecode, uint n) {
-    int typecode_size = mp_binary_get_size(typecode);
+    int typecode_size = mp_binary_get_size('@', typecode, NULL);
     if (typecode_size <= 0) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "bad typecode"));
     }
diff --git a/py/objstr.c b/py/objstr.c
index a682144b8f9e6910cb4961dce47281910030f366..b0d5cba6f17162a8fd866fd6739e1997d9b0f958 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -1415,6 +1415,7 @@ mp_obj_t mp_obj_str_builder_start(const mp_obj_type_t *type, uint len, byte **da
     mp_obj_str_t *o = m_new_obj(mp_obj_str_t);
     o->base.type = type;
     o->len = len;
+    o->hash = 0;
     byte *p = m_new(byte, len + 1);
     o->data = p;
     *data = p;
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index a4df86fda78b646f5ae4d423fb982c1288bd3f68..86a5f2632cc7f6632d4fbc89ea8c99f9554d39ba 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -139,16 +139,10 @@ Q(staticmethod)
 Q(sum)
 Q(super)
 Q(str)
-#if MICROPY_ENABLE_MOD_STRUCT
-Q(struct)
-#endif
 Q(sys)
 Q(to_bytes)
 Q(tuple)
 Q(type)
-#if MICROPY_ENABLE_MOD_STRUCT
-Q(unpack)
-#endif
 Q(value)
 Q(zip)
 
@@ -299,6 +293,12 @@ Q(version)
 Q(version_info)
 #endif
 
+#if MICROPY_ENABLE_MOD_STRUCT
+Q(struct)
+Q(pack)
+Q(unpack)
+#endif
+
 #if MICROPY_ENABLE_PROPERTY
 Q(property)
 Q(getter)
diff --git a/stmhal/adc.c b/stmhal/adc.c
index be83b03ad7c376cfba2e449e779306fafaee07dc..f03017ab4f45649928ef302104579376b8e5b16d 100644
--- a/stmhal/adc.c
+++ b/stmhal/adc.c
@@ -169,7 +169,7 @@ STATIC mp_obj_t adc_read_timed(mp_obj_t self_in, mp_obj_t buf_in, mp_obj_t freq_
 
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_WRITE);
-    int typesize = mp_binary_get_size(bufinfo.typecode);
+    int typesize = mp_binary_get_size('@', bufinfo.typecode, NULL);
 
     // Init TIM6 at the required frequency (in Hz)
     timer_tim6_init(mp_obj_get_int(freq_in));
diff --git a/tests/basics/struct1.py b/tests/basics/struct1.py
index a32979bff9519aaac2200cfa86117b2718fba737..3a05c85f0b36170e413944f79ab73354d6b938e7 100644
--- a/tests/basics/struct1.py
+++ b/tests/basics/struct1.py
@@ -6,3 +6,13 @@ print(struct.unpack(">bI", b"\x80\0\0\x01\0"))
 
 # 32-bit little-endian specific
 #print(struct.unpack("bI", b"\x80\xaa\x55\xaa\0\0\x01\0"))
+
+print(struct.pack("<i", 1))
+print(struct.pack(">i", 1))
+print(struct.pack("<h", 1))
+print(struct.pack(">h", 1))
+print(struct.pack("<b", 1))
+print(struct.pack(">b", 1))
+
+print(struct.pack("<bI", -128, 256))
+print(struct.pack(">bI", -128, 256))
diff --git a/unix/modffi.c b/unix/modffi.c
index 7b8e43874b15bab0811826ea7d0aae772dce9487..bdaa3b2b4325a2a2b9cb20fca3a81f5f84e803c3 100644
--- a/unix/modffi.c
+++ b/unix/modffi.c
@@ -63,7 +63,8 @@ STATIC ffi_type *char2ffi_type(char c)
         case 'L': return &ffi_type_ulong;
         case 'f': return &ffi_type_float;
         case 'd': return &ffi_type_double;
-        case 'p':
+        case 'p': // Deprecated - conflicts with struct module
+        case 'P':
         case 's': return &ffi_type_pointer;
         case 'v': return &ffi_type_void;
         default: return NULL;