diff --git a/cc3200/mods/pybpin.c b/cc3200/mods/pybpin.c
index cae2f68942..debce55288 100644
--- a/cc3200/mods/pybpin.c
+++ b/cc3200/mods/pybpin.c
@@ -60,6 +60,8 @@ DECLARE PRIVATE FUNCTIONS
 ******************************************************************************/
 STATIC pin_obj_t *pin_find_named_pin(const mp_obj_dict_t *named_pins, mp_obj_t name);
 STATIC pin_obj_t *pin_find_pin_by_port_bit (const mp_obj_dict_t *named_pins, uint port, uint bit);
+STATIC int8_t pin_obj_find_af (const pin_obj_t* pin, uint8_t fn, uint8_t unit, uint8_t type);
+STATIC void pin_deassign (pin_obj_t* pin);
 STATIC void pin_obj_configure (const pin_obj_t *self);
 STATIC void pin_get_hibernate_pin_and_idx (const pin_obj_t *self, uint *wake_pin, uint *idx);
 STATIC void pin_extint_enable (mp_obj_t self_in);
@@ -68,6 +70,7 @@ STATIC void pin_extint_register(pin_obj_t *self, uint32_t intmode, uint32_t prio
 STATIC void pin_validate_mode (uint mode);
 STATIC void pin_validate_pull (uint pull);
 STATIC void pin_validate_drive (uint strength);
+STATIC void pin_validate_af(const pin_obj_t* pin, int8_t idx, uint8_t *fn, uint8_t *unit, uint8_t *type);
 STATIC void GPIOA0IntHandler (void);
 STATIC void GPIOA1IntHandler (void);
 STATIC void GPIOA2IntHandler (void);
@@ -115,9 +118,7 @@ void pin_init0(void) {
     mp_map_t *named_map = mp_obj_dict_get_map((mp_obj_t)&pin_board_pins_locals_dict);
     for (uint i = 0; i < named_map->used - 1; i++) {
         pin_obj_t * pin = (pin_obj_t *)named_map->table[i].value;
-        pin_config (pin, PIN_MODE_0, GPIO_DIR_MODE_IN, PIN_TYPE_STD, -1, PIN_STRENGTH_2MA);
-        // mark it as unused again
-        pin->used = false;
+        pin_deassign (pin);
     }
 #endif
 }
@@ -147,10 +148,12 @@ void pin_config (pin_obj_t *self, int af, uint mode, uint pull, int value, uint
     if (af != -1) {
         self->af = af;
     }
+
     // if value is -1, then we want to keep it as it is
     if (value != -1) {
         self->value = value;
     }
+
     // mark the pin as used
     self->used = true;
     pin_obj_configure ((const pin_obj_t *)self);
@@ -160,12 +163,27 @@ void pin_config (pin_obj_t *self, int af, uint mode, uint pull, int value, uint
 }
 
 int8_t pin_find_af_index (const pin_obj_t* pin, uint8_t fn, uint8_t unit, uint8_t type) {
-    for (int i = 0; i < pin->num_afs; i++) {
-        if (pin->af_list[i].fn == fn && pin->af_list[i].unit == unit && pin->af_list[i].type == type) {
-            return pin->af_list[i].idx;
+    int8_t af = pin_obj_find_af(pin, fn, unit, type);
+    if (af < 0) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, mpexception_value_invalid_arguments));
+    }
+    return af;
+}
+
+void pin_free_af_from_pins (uint8_t fn, uint8_t unit, uint8_t type) {
+    mp_map_t *named_map = mp_obj_dict_get_map((mp_obj_t)&pin_board_pins_locals_dict);
+    for (uint i = 0; i < named_map->used - 1; i++) {
+        pin_obj_t * pin = (pin_obj_t *)named_map->table[i].value;
+        // af is different than GPIO
+        if (pin->af > PIN_MODE_0) {
+            // check if the pin supports the target af
+            int af = pin_obj_find_af(pin, fn, unit, type);
+            if (af > 0 && af == pin->af) {
+                // the pin is assigned to the target af, de-assign it
+                pin_deassign (pin);
+            }
         }
     }
-    nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, mpexception_value_invalid_arguments));
 }
 
 /******************************************************************************
@@ -191,6 +209,20 @@ STATIC pin_obj_t *pin_find_pin_by_port_bit (const mp_obj_dict_t *named_pins, uin
     return NULL;
 }
 
+STATIC int8_t pin_obj_find_af (const pin_obj_t* pin, uint8_t fn, uint8_t unit, uint8_t type) {
+    for (int i = 0; i < pin->num_afs; i++) {
+        if (pin->af_list[i].fn == fn && pin->af_list[i].unit == unit && pin->af_list[i].type == type) {
+            return pin->af_list[i].idx;
+        }
+    }
+    return -1;
+}
+
+STATIC void pin_deassign (pin_obj_t* pin) {
+    pin_config (pin, PIN_MODE_0, GPIO_DIR_MODE_IN, PIN_TYPE_STD, -1, PIN_STRENGTH_4MA);
+    pin->used = false;
+}
+
 STATIC void pin_obj_configure (const pin_obj_t *self) {
     uint32_t type;
     if (self->mode == PIN_TYPE_ANALOG) {
@@ -370,6 +402,18 @@ STATIC void pin_validate_drive(uint strength) {
     }
 }
 
+STATIC void pin_validate_af(const pin_obj_t* pin, int8_t idx, uint8_t *fn, uint8_t *unit, uint8_t *type) {
+    for (int i = 0; i < pin->num_afs; i++) {
+        if (pin->af_list[i].idx == idx) {
+            *fn = pin->af_list[i].fn;
+            *unit = pin->af_list[i].unit;
+            *type = pin->af_list[i].type;
+            return;
+        }
+    }
+    nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, mpexception_value_invalid_arguments));
+}
+
 STATIC void GPIOA0IntHandler (void) {
     EXTI_Handler(GPIOA0_BASE);
 }
@@ -455,6 +499,12 @@ STATIC mp_obj_t pin_obj_init_helper(pin_obj_t *self, mp_uint_t n_args, const mp_
         goto invalid_args;
     }
 
+    // check for a valid af and then free it from any other pins
+    if (af > PIN_MODE_0) {
+        uint8_t fn, unit, type;
+        pin_validate_af (self, af, &fn, &unit, &type);
+        pin_free_af_from_pins(fn, unit, type);
+    }
     pin_config (self, af, mode, pull, value, strength);
 
     return mp_const_none;
diff --git a/cc3200/mods/pybpin.h b/cc3200/mods/pybpin.h
index 4c49e63ab5..f03a998f53 100644
--- a/cc3200/mods/pybpin.h
+++ b/cc3200/mods/pybpin.h
@@ -140,5 +140,6 @@ void pin_init0(void);
 void pin_config(pin_obj_t *self, int af, uint mode, uint type, int value, uint strength);
 pin_obj_t *pin_find(mp_obj_t user_obj);
 int8_t pin_find_af_index(const pin_obj_t* pin, uint8_t fn, uint8_t unit, uint8_t type);
+void pin_free_af_from_pins (uint8_t fn, uint8_t unit, uint8_t type);
 
 #endif  // PYBPIN_H_
diff --git a/cc3200/mods/pybuart.c b/cc3200/mods/pybuart.c
index cb010395bd..00f009ce67 100644
--- a/cc3200/mods/pybuart.c
+++ b/cc3200/mods/pybuart.c
@@ -71,11 +71,18 @@
 
 #define PYBUART_RX_BUFFER_LEN                   (128)
 
+// interrupt triggers
+#define E_UART_TRIGGER_RX_ANY                   (0x01)
+#define E_UART_TRIGGER_RX_HALF                  (0x02)
+#define E_UART_TRIGGER_RX_FULL                  (0x04)
+#define E_UART_TRIGGER_TX_DONE                  (0x08)
+
 /******************************************************************************
  DECLARE PRIVATE FUNCTIONS
  ******************************************************************************/
 STATIC void uart_init (pyb_uart_obj_t *self);
 STATIC bool uart_rx_wait (pyb_uart_obj_t *self);
+STATIC void uart_check_init(pyb_uart_obj_t *self);
 STATIC void UARTGenericIntHandler(uint32_t uart_id);
 STATIC void UART0IntHandler(void);
 STATIC void UART1IntHandler(void);
@@ -98,6 +105,7 @@ struct _pyb_uart_obj_t {
     uint16_t read_buf_tail;             // indexes first full slot (not full if equals head)
     byte peripheral;
     byte irq_trigger;
+    bool callback_enabled;
 };
 
 /******************************************************************************
@@ -244,6 +252,7 @@ STATIC bool uart_rx_wait (pyb_uart_obj_t *self) {
 STATIC void UARTGenericIntHandler(uint32_t uart_id) {
     pyb_uart_obj_t *self;
     uint32_t status;
+    bool exec_callback = false;
 
     self = &pyb_uart_obj[uart_id];
     status = MAP_UARTIntStatus(self->reg, true);
@@ -266,9 +275,23 @@ STATIC void UARTGenericIntHandler(uint32_t uart_id) {
                 }
             }
         }
-        // call the user defined handler
-        mp_obj_t _callback = mpcallback_find(self);
-        mpcallback_handler(_callback);
+
+        if (self->irq_trigger & E_UART_TRIGGER_RX_ANY) {
+            exec_callback = true;
+        }
+
+        if (exec_callback && self->callback_enabled) {
+            // call the user defined handler
+            mp_obj_t _callback = mpcallback_find(self);
+            mpcallback_handler(_callback);
+        }
+    }
+}
+
+STATIC void uart_check_init(pyb_uart_obj_t *self) {
+    // not initialized
+    if (!self->baudrate) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_request_not_possible));
     }
 }
 
@@ -287,11 +310,12 @@ STATIC void uart_callback_enable (mp_obj_t self_in) {
         MAP_UARTIntClear(self->reg, UART_INT_RX | UART_INT_RT);
         MAP_UARTIntEnable(self->reg, UART_INT_RX | UART_INT_RT);
     }
+    self->callback_enabled = true;
 }
 
 STATIC void uart_callback_disable (mp_obj_t self_in) {
     pyb_uart_obj_t *self = self_in;
-    MAP_UARTIntDisable(self->reg, UART_INT_RX | UART_INT_RT);
+    self->callback_enabled = false;
 }
 
 /******************************************************************************/
@@ -405,6 +429,7 @@ STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, mp_uint_t n_args, con
             }
             // the pins tuple passed looks good so far
             for (int i = 0; i < n_pins; i++) {
+                pin_free_af_from_pins(PIN_FN_UART, self->uart_id, i);
                 if (pins_t[i] != mp_const_none) {
                     pin_obj_t *pin = pin_find(pins_t[i]);
                     pin_config (pin, pin_find_af_index(pin, PIN_FN_UART, self->uart_id, i),
@@ -422,6 +447,8 @@ STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, mp_uint_t n_args, con
     uart_init (self);
     // register it with the sleep module
     pybsleep_add ((const mp_obj_t)self, (WakeUpCB_t)uart_init);
+    // enable the callback
+    uart_callback_new (self, mp_const_none, INT_PRIORITY_LVL_3, E_UART_TRIGGER_RX_ANY);
 
     return mp_const_none;
 
@@ -478,12 +505,14 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_deinit_obj, pyb_uart_deinit);
 
 STATIC mp_obj_t pyb_uart_any(mp_obj_t self_in) {
     pyb_uart_obj_t *self = self_in;
+    uart_check_init(self);
     return mp_obj_new_int(uart_rx_any(self));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_any_obj, pyb_uart_any);
 
 STATIC mp_obj_t pyb_uart_sendbreak(mp_obj_t self_in) {
     pyb_uart_obj_t *self = self_in;
+    uart_check_init(self);
     // send a break signal for at least 2 complete frames
     MAP_UARTBreakCtl(self->reg, true);
     UtilsDelay(UTILS_DELAY_US_TO_COUNT(PYBUART_2_FRAMES_TIME_US(self->baudrate)));
@@ -498,6 +527,7 @@ STATIC mp_obj_t pyb_uart_callback (mp_uint_t n_args, const mp_obj_t *pos_args, m
 
     // check if any parameters were passed
     pyb_uart_obj_t *self = pos_args[0];
+    uart_check_init(self);
     mp_obj_t _callback = mpcallback_find((mp_obj_t)self);
     if (kw_args->used > 0) {
 
@@ -547,6 +577,7 @@ STATIC MP_DEFINE_CONST_DICT(pyb_uart_locals_dict, pyb_uart_locals_dict_table);
 STATIC mp_uint_t pyb_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
     pyb_uart_obj_t *self = self_in;
     byte *buf = buf_in;
+    uart_check_init(self);
 
     // make sure we want at least 1 char
     if (size == 0) {
@@ -574,6 +605,7 @@ STATIC mp_uint_t pyb_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, i
 STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t size, int *errcode) {
     pyb_uart_obj_t *self = self_in;
     const char *buf = buf_in;
+    uart_check_init(self);
 
     // write the data
     if (!uart_tx_strn(self, buf, size)) {
@@ -585,6 +617,8 @@ STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t
 STATIC mp_uint_t pyb_uart_ioctl(mp_obj_t self_in, mp_uint_t request, mp_uint_t arg, int *errcode) {
     pyb_uart_obj_t *self = self_in;
     mp_uint_t ret;
+    uart_check_init(self);
+
     if (request == MP_IOCTL_POLL) {
         mp_uint_t flags = arg;
         ret = 0;
diff --git a/cc3200/mods/pybuart.h b/cc3200/mods/pybuart.h
index 476fc11a4e..89f3edc0ed 100644
--- a/cc3200/mods/pybuart.h
+++ b/cc3200/mods/pybuart.h
@@ -28,12 +28,6 @@
 #ifndef PYBUART_H_
 #define PYBUART_H_
 
-// interrupt triggers
-#define E_UART_TRIGGER_RX_ANY                   (0x01)
-#define E_UART_TRIGGER_RX_HALF                  (0x02)
-#define E_UART_TRIGGER_RX_FULL                  (0x04)
-#define E_UART_TRIGGER_TX_DONE                  (0x08)
-
 typedef enum {
     PYB_UART_0      =  0,
     PYB_UART_1      =  1,
diff --git a/cc3200/mptask.c b/cc3200/mptask.c
index 87990b43c2..dd3a762244 100644
--- a/cc3200/mptask.c
+++ b/cc3200/mptask.c
@@ -145,7 +145,6 @@ soft_reset:
             mp_obj_new_int(MICROPY_STDIO_UART_BAUD),
     };
     pyb_stdio_uart = pyb_uart_type.make_new((mp_obj_t)&pyb_uart_type, MP_ARRAY_SIZE(args), 0, args);
-    uart_callback_new (pyb_stdio_uart, mp_const_none, INT_PRIORITY_LVL_3, E_UART_TRIGGER_RX_ANY);
 #else
     pyb_stdio_uart = MP_OBJ_NULL;
 #endif
diff --git a/tests/wipy/pin.py b/tests/wipy/pin.py
index 20bea3e5a7..ae0fa82b19 100644
--- a/tests/wipy/pin.py
+++ b/tests/wipy/pin.py
@@ -7,10 +7,10 @@ import os
 machine = os.uname().machine
 if 'LaunchPad' in machine:
     pin_map = ['GP24', 'GP12', 'GP14', 'GP15', 'GP16', 'GP17', 'GP28', 'GP8', 'GP6', 'GP30', 'GP31', 'GP3', 'GP0', 'GP4', 'GP5']
-    af_range = range(1, 16)
+    max_af_idx = 15
 elif 'WiPy' in machine:
     pin_map = ['GP23', 'GP24', 'GP12', 'GP13', 'GP14', 'GP9', 'GP17', 'GP28', 'GP22', 'GP8', 'GP30', 'GP31', 'GP0', 'GP4', 'GP5']
-    af_range = range(1, 16)
+    max_af_idx = 15
 else:
     raise Exception('Board not supported!')
 
@@ -28,9 +28,10 @@ def test_pin_read(pull):
 
 def test_pin_af():
     for p in pin_map:
-        for n in af_range:
-            Pin(p, mode=Pin.ALT, alt=n)
-            Pin(p, mode=Pin.ALT_OPEN_DRAIN, alt=n)
+        for af in Pin(p).alt_list():
+            if af[1] <= max_af_idx:
+                Pin(p, mode=Pin.ALT, alt=af[1])
+                Pin(p, mode=Pin.ALT_OPEN_DRAIN, alt=af[1])
 
 # test un-initialized pins
 test_noinit()
@@ -67,10 +68,6 @@ pin.init(mode=Pin.OUT, pull=Pin.PULL_UP, drive=pin.LOW_POWER)
 print(pin)
 pin.init(mode=Pin.OUT, pull=Pin.PULL_UP, drive=pin.HIGH_POWER)
 print(pin)
-pin = Pin(pin_map[0], Pin.ALT, Pin.PULL_NONE, alt=1)
-print(pin)
-pin = Pin(pin_map[0], Pin.ALT_OPEN_DRAIN, Pin.PULL_NONE, alt=15)
-print(pin)
 
 # test value in OUT mode
 pin = Pin(pin_map[0], mode=Pin.OUT)
diff --git a/tests/wipy/pin.py.exp b/tests/wipy/pin.py.exp
index 87b4d3ef85..4fc60b5d79 100644
--- a/tests/wipy/pin.py.exp
+++ b/tests/wipy/pin.py.exp
@@ -32,8 +32,6 @@ Pin('GP23', mode=Pin.IN, pull=Pin.PULL_NONE, drive=Pin.MED_POWER, alt=-1)
 Pin('GP23', mode=Pin.IN, pull=Pin.PULL_DOWN, drive=Pin.MED_POWER, alt=-1)
 Pin('GP23', mode=Pin.OUT, pull=Pin.PULL_UP, drive=Pin.LOW_POWER, alt=-1)
 Pin('GP23', mode=Pin.OUT, pull=Pin.PULL_UP, drive=Pin.HIGH_POWER, alt=-1)
-Pin('GP23', mode=Pin.ALT, pull=Pin.PULL_NONE, drive=Pin.MED_POWER, alt=1)
-Pin('GP23', mode=Pin.ALT_OPEN_DRAIN, pull=Pin.PULL_NONE, drive=Pin.MED_POWER, alt=15)
 1
 0
 1
diff --git a/tests/wipy/uart.py b/tests/wipy/uart.py
index a483891ad8..31a2c3a0ab 100644
--- a/tests/wipy/uart.py
+++ b/tests/wipy/uart.py
@@ -6,6 +6,7 @@ UART0 and UART1 must be connected together for this test to pass.
 from pyb import UART
 from pyb import Pin
 import os
+import pyb
 
 machine = os.uname().machine
 if 'LaunchPad' in machine:
@@ -25,12 +26,6 @@ for uart_id in uart_id_range:
     uart.init(baudrate=115200, parity=1, pins=uart_pins[uart_id][0])
     uart.sendbreak()
 
-# assign GP1, GP2, GP3 and GP4 back to GPIO mode
-Pin('GP1', mode=Pin.IN)
-Pin('GP2', mode=Pin.IN)
-Pin('GP3', mode=Pin.IN)
-Pin('GP4', mode=Pin.IN)
-
 # now it's time for some loopback tests between the uarts
 uart0 = UART(0, 1000000, pins=uart_pins[0][0])
 print(uart0)
@@ -52,16 +47,16 @@ print(buf)
 print(uart1.readinto(buf) == 2)
 print(buf)
 
-uart0.write(b'123')
-print(uart1.any() > 0)
-print(uart1.readline() == b'123')
+uart0.write(b'1234567890')
+pyb.delay(2) # because of the fifo interrupt levels
+print(uart1.any() == 10)
+print(uart1.readline() == b'1234567890')
 print(uart1.any() == 0)
 
 uart0.write(b'1234567890')
 print(uart1.readall() == b'1234567890')
 
 # tx only mode
-Pin('GP13', mode=Pin.IN)
 uart0 = UART(0, 1000000, pins=('GP12', None))
 print(uart0.write(b'123456') == 6)
 print(uart1.read() == b'123456')
@@ -69,17 +64,21 @@ print(uart1.write(b'123') == 3)
 print(uart0.read() == b'')
 
 # rx only mode
-Pin('GP12', mode=Pin.IN)
 uart0 = UART(0, 1000000, pins=(None, 'GP13'))
 print(uart0.write(b'123456') == 6)
 print(uart1.read() == b'')
 print(uart1.write(b'123') == 3)
 print(uart0.read() == b'123')
 
-Pin('GP13', mode=Pin.IN)
-Pin('GP12', mode=Pin.IN)
-# no pin assignemnt
+# leave pins as they were (rx only mode)
 uart0 = UART(0, 1000000, pins=None)
+print(uart0.write(b'123456') == 6)
+print(uart1.read() == b'')
+print(uart1.write(b'123') == 3)
+print(uart0.read() == b'123')
+
+# no pin assignemnt
+uart0 = UART(0, 1000000, pins=(None, None))
 print(uart0.write(b'123456789') == 9)
 print(uart1.read() == b'')
 print(uart1.write(b'123456789') == 9)
@@ -87,12 +86,46 @@ print(uart0.read() == b'')
 print(Pin.board.GP12)
 print(Pin.board.GP13)
 
+# check for memory leaks...
+for i in range (0, 1000):
+    uart0 = UART(0, 1000000)
+    uart1 = UART(1, 1000000)
+
 # next ones must raise
 try:
     UART(0, 9600, parity=2, pins=('GP12', 'GP13', 'GP7'))
 except Exception:
     print('Exception')
+
 try:
     UART(0, 9600, parity=2, pins=('GP12', 'GP7'))
 except Exception:
     print('Exception')
+
+uart0 = UART(0, 1000000)
+uart0.deinit()
+try:
+    uart0.any()
+except Exception:
+    print('Exception')
+
+uart0 = UART(0, 1000000)
+uart0.deinit()
+try:
+    uart0.read()
+except Exception:
+    print('Exception')
+
+uart0 = UART(0, 1000000)
+uart0.deinit()
+try:
+    uart0.write('abc')
+except Exception:
+    print('Exception')
+
+uart0 = UART(0, 1000000)
+uart0.deinit()
+try:
+    uart0.sendbreak('abc')
+except Exception:
+    print('Exception')
diff --git a/tests/wipy/uart.py.exp b/tests/wipy/uart.py.exp
index a5c6da1e8f..7234b35190 100644
--- a/tests/wipy/uart.py.exp
+++ b/tests/wipy/uart.py.exp
@@ -28,7 +28,15 @@ True
 True
 True
 True
+True
+True
+True
+True
 Pin('GP12', mode=Pin.IN, pull=Pin.PULL_NONE, drive=Pin.MED_POWER, alt=-1)
 Pin('GP13', mode=Pin.IN, pull=Pin.PULL_NONE, drive=Pin.MED_POWER, alt=-1)
 Exception
 Exception
+Exception
+Exception
+Exception
+Exception