diff --git a/extmod/modselect.c b/extmod/modselect.c
index 90f861e9c609bfcb656e829217b60e5c08270691..64f0517bdc091fbfee016e48530b200d60387838 100644
--- a/extmod/modselect.c
+++ b/extmod/modselect.c
@@ -42,15 +42,16 @@
 ///
 /// This module provides the select function.
 
-/// \function select(rlist, wlist, xlist[, timeout])
-mp_obj_t select_select(uint n_args, const mp_obj_t *args) {
-    return mp_obj_new_bytes((void*)mp_obj_int_get(ptr), mp_obj_int_get(size));
-}
-MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(select_select_obj, 3, 4, select_select);
+// This is just a skeleton.  Individual functions must be implemented by a port.
+// For the following, specific types don't matter, only addresses.
+struct _dummy_t;
+extern struct _dummy_t mp_select_select_obj;
+extern struct _dummy_t mp_select_poll_obj;
 
 STATIC const mp_map_elem_t mp_module_select_globals_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_select) },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_select), (mp_obj_t)&select_select_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_select), (mp_obj_t)&mp_select_select_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_poll), (mp_obj_t)&mp_select_poll_obj },
 };
 
 STATIC const mp_obj_dict_t mp_module_select_globals = {
diff --git a/py/builtin.h b/py/builtin.h
index 1bb61f6ebcdc1d3d9f3aef76e8ac5c8543fec4ba..2ccd4481a25c97ae1005056c4ab72c5382056533 100644
--- a/py/builtin.h
+++ b/py/builtin.h
@@ -89,3 +89,4 @@ extern struct _dummy_t mp_sys_stderr_obj;
 // extmod modules
 extern const mp_obj_module_t mp_module_uctypes;
 extern const mp_obj_module_t mp_module_zlibd;
+extern const mp_obj_module_t mp_module_select;
diff --git a/py/builtintables.c b/py/builtintables.c
index 08b6b164937dfb8c15e8de134dd144ffe0860392..ad2e0bb55f25a5485d6b15a60b103307c4eae9d8 100644
--- a/py/builtintables.c
+++ b/py/builtintables.c
@@ -200,6 +200,9 @@ STATIC const mp_map_elem_t mp_builtin_module_table[] = {
 #if MICROPY_PY_ZLIBD
     { MP_OBJ_NEW_QSTR(MP_QSTR_zlibd), (mp_obj_t)&mp_module_zlibd },
 #endif
+#if MICROPY_PY_SELECT
+    { MP_OBJ_NEW_QSTR(MP_QSTR_select), (mp_obj_t)&mp_module_select },
+#endif
 
     // extra builtin modules as defined by a port
     MICROPY_PORT_BUILTIN_MODULES
diff --git a/py/obj.h b/py/obj.h
index 79f3041500dda5f6edeee9b93280ca6940cf17db..03ad347e26c4fdb222b8bf7f6ae39d0a674ef1c4 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -237,7 +237,7 @@ typedef struct _mp_stream_p_t {
     // are implementation-dependent, but will be exposed to user, e.g. via exception).
     mp_uint_t (*read)(mp_obj_t obj, void *buf, mp_uint_t size, int *errcode);
     mp_uint_t (*write)(mp_obj_t obj, const void *buf, mp_uint_t size, int *errcode);
-    mp_uint_t (*ioctl(mp_obj_t obj, mp_uint_t request, int *errcode, ...);
+    mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, int *errcode, ...);
     mp_uint_t is_text : 1; // default is bytes, set this for text stream
 } mp_stream_p_t;
 
diff --git a/py/py.mk b/py/py.mk
index e2288d3821c679d3edaebafc96d4450f035cd619..9101704b7e57276a081fbb55aaa0aeeacd48cab1 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -112,6 +112,7 @@ PY_O_BASENAME = \
 	pfenv_printf.o \
 	../extmod/moductypes.o \
 	../extmod/modzlibd.o \
+	../extmod/modselect.o \
 
 # prepend the build destination prefix to the py object files
 PY_O = $(addprefix $(PY_BUILD)/, $(PY_O_BASENAME))
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index d41029a1fa642237eaa2b70409ca18e3a351843f..68681e47beec89441294af2be4c888a03222f5cf 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -463,3 +463,11 @@ Q(deleter)
 Q(zlibd)
 Q(decompress)
 #endif
+
+#if MICROPY_PY_SELECT
+Q(select)
+Q(poll)
+Q(register)
+Q(unregister)
+Q(modify)
+#endif
diff --git a/stmhal/Makefile b/stmhal/Makefile
index a918b1cc00dd9647d030115f3a64fee7c54736d0..3ae1805b17a6b0d2a38240fa549aefebb7caeed5 100644
--- a/stmhal/Makefile
+++ b/stmhal/Makefile
@@ -102,6 +102,7 @@ SRC_C = \
 	modpyb.c \
 	modstm.c \
 	modtime.c \
+	modselect.c \
 	import.c \
 	lexerfatfs.c \
 	extint.c \
diff --git a/stmhal/modselect.c b/stmhal/modselect.c
new file mode 100644
index 0000000000000000000000000000000000000000..6b58c04bb8bfe0f9c432f4dcbc1f4c48819ec82c
--- /dev/null
+++ b/stmhal/modselect.c
@@ -0,0 +1,285 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 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 <stdint.h>
+#include <stdio.h>
+
+#include "stm32f4xx_hal.h"
+
+#include "mpconfig.h"
+#include "misc.h"
+#include "nlr.h"
+#include "qstr.h"
+#include "obj.h"
+#include "objlist.h"
+
+/// \moduleref select
+
+#define MP_IOCTL_POLL (0x100 | 1)
+
+#define MP_IOCTL_POLL_RD  (0x0001)
+#define MP_IOCTL_POLL_WR  (0x0002)
+#define MP_IOCTL_POLL_HUP (0x0004)
+#define MP_IOCTL_POLL_ERR (0x0008)
+
+typedef struct _poll_obj_t {
+    mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, int *errcode, ...);
+    mp_uint_t flags;
+    mp_uint_t flags_ret;
+} poll_obj_t;
+
+STATIC void poll_map_add(mp_map_t *poll_map, const mp_obj_t *obj, mp_uint_t obj_len, mp_uint_t flags, bool or_flags) {
+    for (mp_uint_t i = 0; i < obj_len; i++) {
+        mp_map_elem_t *elem = mp_map_lookup(poll_map, obj[i], MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
+        if (elem->value == NULL) {
+            // object not found; get its ioctl and add it to the poll list
+            mp_obj_type_t *type = mp_obj_get_type(obj[i]);
+            if (type->stream_p == NULL || type->stream_p->ioctl == NULL) {
+                nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "object with stream.ioctl required"));
+            }
+            poll_obj_t *poll_obj = m_new_obj(poll_obj_t);
+            poll_obj->ioctl = type->stream_p->ioctl;
+            poll_obj->flags = flags;
+            poll_obj->flags_ret = 0;
+            elem->value = poll_obj;
+        } else {
+            // object exists; update its flags
+            if (or_flags) {
+                ((poll_obj_t*)elem->value)->flags |= flags;
+            } else {
+                ((poll_obj_t*)elem->value)->flags = flags;
+            }
+        }
+    }
+}
+
+// poll each object in the map
+STATIC mp_uint_t poll_map_poll(mp_map_t *poll_map, mp_uint_t *rwx_num) {
+    mp_uint_t n_ready = 0;
+    for (mp_uint_t i = 0; i < poll_map->alloc; ++i) {
+        if (!MP_MAP_SLOT_IS_FILLED(poll_map, i)) {
+            continue;
+        }
+
+        poll_obj_t *poll_obj = (poll_obj_t*)poll_map->table[i].value;
+        int errno;
+        mp_int_t ret = poll_obj->ioctl(poll_map->table[i].key, MP_IOCTL_POLL, &errno, poll_obj->flags);
+        poll_obj->flags_ret = ret;
+
+        if (ret == -1) {
+            // error doing ioctl
+            nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
+        }
+
+        if (ret != 0) {
+            // object is ready
+            n_ready += 1;
+            if (rwx_num != NULL) {
+                if (ret & MP_IOCTL_POLL_RD) {
+                    rwx_num[0] += 1;
+                }
+                if (ret & MP_IOCTL_POLL_WR) {
+                    rwx_num[1] += 1;
+                }
+                if ((ret & ~(MP_IOCTL_POLL_RD | MP_IOCTL_POLL_WR)) != 0) {
+                    rwx_num[2] += 1;
+                }
+            }
+        }
+    }
+    return n_ready;
+}
+
+/// \function select(rlist, wlist, xlist[, timeout])
+STATIC mp_obj_t select_select(uint n_args, const mp_obj_t *args) {
+    // get array data from tuple/list arguments
+    mp_uint_t rwx_len[3];
+    mp_obj_t *r_array, *w_array, *x_array;
+    mp_obj_get_array(args[0], &rwx_len[0], &r_array);
+    mp_obj_get_array(args[1], &rwx_len[1], &w_array);
+    mp_obj_get_array(args[2], &rwx_len[2], &x_array);
+
+    // get timeout
+    mp_uint_t timeout = -1;
+    if (n_args == 4) {
+        if (args[3] != mp_const_none) {
+            float timeout_f = mp_obj_get_float(args[3]);
+            if (timeout_f >= 0) {
+                timeout = (mp_uint_t)(timeout_f * 1000);
+            }
+        }
+    }
+
+    // merge separate lists and get the ioctl function for each object
+    mp_map_t poll_map;
+    mp_map_init(&poll_map, rwx_len[0] + rwx_len[1] + rwx_len[2]);
+    poll_map_add(&poll_map, r_array, rwx_len[0], MP_IOCTL_POLL_RD, true);
+    poll_map_add(&poll_map, w_array, rwx_len[1], MP_IOCTL_POLL_WR, true);
+    poll_map_add(&poll_map, x_array, rwx_len[2], MP_IOCTL_POLL_ERR | MP_IOCTL_POLL_HUP, true);
+
+    mp_uint_t start_tick = HAL_GetTick();
+    rwx_len[0] = rwx_len[1] = rwx_len[2] = 0;
+    for (;;) {
+        // poll the objects
+        mp_uint_t n_ready = poll_map_poll(&poll_map, rwx_len);
+
+        if (n_ready > 0 || (timeout != -1 && HAL_GetTick() - start_tick >= timeout)) {
+            // one or more objects are ready, or we had a timeout
+            mp_obj_t list_array[3];
+            list_array[0] = mp_obj_new_list(rwx_len[0], NULL);
+            list_array[1] = mp_obj_new_list(rwx_len[1], NULL);
+            list_array[2] = mp_obj_new_list(rwx_len[2], NULL);
+            rwx_len[0] = rwx_len[1] = rwx_len[2] = 0;
+            for (mp_uint_t i = 0; i < poll_map.alloc; ++i) {
+                if (!MP_MAP_SLOT_IS_FILLED(&poll_map, i)) {
+                    continue;
+                }
+                poll_obj_t *poll_obj = (poll_obj_t*)poll_map.table[i].value;
+                if (poll_obj->flags_ret & MP_IOCTL_POLL_RD) {
+                    ((mp_obj_list_t*)list_array[0])->items[rwx_len[0]++] = poll_map.table[i].key;
+                }
+                if (poll_obj->flags_ret & MP_IOCTL_POLL_WR) {
+                    ((mp_obj_list_t*)list_array[1])->items[rwx_len[1]++] = poll_map.table[i].key;
+                }
+                if ((poll_obj->flags_ret & ~(MP_IOCTL_POLL_RD | MP_IOCTL_POLL_WR)) != 0) {
+                    ((mp_obj_list_t*)list_array[2])->items[rwx_len[2]++] = poll_map.table[i].key;
+                }
+            }
+            mp_map_deinit(&poll_map);
+            return mp_obj_new_tuple(3, list_array);
+        }
+        __WFI();
+    }
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_select_select_obj, 3, 4, select_select);
+
+/// \class Poll
+
+typedef struct _mp_obj_poll_t {
+    mp_obj_base_t base;
+    mp_map_t poll_map;
+} mp_obj_poll_t;
+
+/// \method register(obj[, eventmask])
+STATIC mp_obj_t poll_register(uint n_args, const mp_obj_t *args) {
+    mp_obj_poll_t *self = args[0];
+    mp_uint_t flags;
+    if (n_args == 3) {
+        flags = mp_obj_get_int(args[2]);
+    } else {
+        flags = MP_IOCTL_POLL_RD | MP_IOCTL_POLL_WR;
+    }
+    poll_map_add(&self->poll_map, &args[1], 1, flags, false);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_register_obj, 2, 3, poll_register);
+
+/// \method unregister(obj)
+STATIC mp_obj_t poll_unregister(mp_obj_t self_in, mp_obj_t obj_in) {
+    mp_obj_poll_t *self = self_in;
+    mp_map_lookup(&self->poll_map, obj_in, MP_MAP_LOOKUP_REMOVE_IF_FOUND);
+    // TODO raise KeyError if obj didn't exist in map
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(poll_unregister_obj, poll_unregister);
+
+/// \method modify(obj, eventmask)
+STATIC mp_obj_t poll_modify(mp_obj_t self_in, mp_obj_t obj_in, mp_obj_t eventmask_in) {
+    mp_obj_poll_t *self = self_in;
+    mp_map_elem_t *elem = mp_map_lookup(&self->poll_map, obj_in, MP_MAP_LOOKUP);
+    if (elem == NULL) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_IOError, "object was never registered"));
+    }
+    ((poll_obj_t*)elem->value)->flags = mp_obj_get_int(eventmask_in);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(poll_modify_obj, poll_modify);
+
+/// \method poll([timeout])
+/// Timeout is in milliseconds.
+STATIC mp_obj_t poll_poll(uint n_args, const mp_obj_t *args) {
+    mp_obj_poll_t *self = args[0];
+
+    // work out timeout (its given already in ms)
+    mp_uint_t timeout = -1;
+    if (n_args == 2) {
+        if (args[1] != mp_const_none) {
+            mp_int_t timeout_i = mp_obj_get_int(args[1]);
+            if (timeout_i >= 0) {
+                timeout = timeout_i;
+            }
+        }
+    }
+
+    mp_uint_t start_tick = HAL_GetTick();
+    for (;;) {
+        // poll the objects
+        mp_uint_t n_ready = poll_map_poll(&self->poll_map, NULL);
+
+        if (n_ready > 0 || (timeout != -1 && HAL_GetTick() - start_tick >= timeout)) {
+            // one or more objects are ready, or we had a timeout
+            mp_obj_list_t *ret_list = mp_obj_new_list(n_ready, NULL);
+            mp_uint_t n_ready = 0;
+            for (mp_uint_t i = 0; i < self->poll_map.alloc; ++i) {
+                if (!MP_MAP_SLOT_IS_FILLED(&self->poll_map, i)) {
+                    continue;
+                }
+                poll_obj_t *poll_obj = (poll_obj_t*)self->poll_map.table[i].value;
+                if (poll_obj->flags_ret != 0) {
+                    mp_obj_t tuple[2] = {self->poll_map.table[i].key, MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret)};
+                    ret_list->items[n_ready++] = mp_obj_new_tuple(2, tuple);
+                }
+            }
+            mp_map_deinit(&self->poll_map);
+            return ret_list;
+        }
+        __WFI();
+    }
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_poll_obj, 1, 2, poll_poll);
+
+STATIC const mp_map_elem_t poll_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_register), (mp_obj_t)&poll_register_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_unregister), (mp_obj_t)&poll_unregister_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_modify), (mp_obj_t)&poll_modify_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_poll), (mp_obj_t)&poll_poll_obj },
+};
+STATIC MP_DEFINE_CONST_DICT(poll_locals_dict, poll_locals_dict_table);
+
+STATIC const mp_obj_type_t mp_type_poll = {
+    { &mp_type_type },
+    .name = MP_QSTR_poll,
+    .locals_dict = (mp_obj_t)&poll_locals_dict,
+};
+
+/// \function poll()
+STATIC mp_obj_t select_poll(void) {
+    mp_obj_poll_t *poll = m_new_obj(mp_obj_poll_t);
+    poll->base.type = &mp_type_poll;
+    mp_map_init(&poll->poll_map, 0);
+    return poll;
+}
+MP_DEFINE_CONST_FUN_OBJ_0(mp_select_poll_obj, select_poll);
diff --git a/stmhal/mpconfigport.h b/stmhal/mpconfigport.h
index 860ea77071779d6206b8caa9a1be911be5c98347..13656044172c71085b74cdd0c70190cf6a83126d 100644
--- a/stmhal/mpconfigport.h
+++ b/stmhal/mpconfigport.h
@@ -57,6 +57,7 @@
 #define MICROPY_PY_IO_FILEIO        (1)
 #define MICROPY_PY_UCTYPES          (1)
 #define MICROPY_PY_ZLIBD            (1)
+#define MICROPY_PY_SELECT           (1)
 
 #define MICROPY_ENABLE_EMERGENCY_EXCEPTION_BUF   (1)
 #define MICROPY_EMERGENCY_EXCEPTION_BUF_SIZE  (0)