diff --git a/ports/samd/machine_pin.c b/ports/samd/machine_pin.c
index 5f9cbfb99b..49aecba011 100644
--- a/ports/samd/machine_pin.c
+++ b/ports/samd/machine_pin.c
@@ -31,35 +31,25 @@
 #include "extmod/virtpin.h"
 #include "modmachine.h"
 #include "samd_soc.h"
-#include "pins.h" // boards/<BOARD>/
+#include "pins.h"
 
-// ASF4 (MCU package specific pin defs in 'boards')
 #include "hal_gpio.h"
-#include "hpl_gpio.h"
-#include "hal_atomic.h"
 
 #define GPIO_MODE_IN (0)
 #define GPIO_MODE_OUT (1)
-// #define GPIO_MODE_ALT (3)
+#define GPIO_MODE_OPEN_DRAIN (2)
 
 #define GPIO_STRENGTH_2MA (0)
 #define GPIO_STRENGTH_8MA (1)
 
-// asf4 hpl_gpio.h gpio_pull_mode
+uint32_t machine_pin_open_drain_mask[4];
 
-/*
-typedef struct _machine_pin_irq_obj_t {
-    mp_irq_obj_t base;
-    uint32_t flags;
-    uint32_t trigger;
-} machine_pin_irq_obj_t;
-
-STATIC const mp_irq_methods_t machine_pin_irq_methods;
-*/
+// Open drain behaviour is simulated.
+#define GPIO_IS_OPEN_DRAIN(id) (machine_pin_open_drain_mask[id / 32] & (1 << (id % 32)))
 
 STATIC void machine_pin_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     machine_pin_obj_t *self = self_in;
-    mp_printf(print, "Pin(%u)", self->id);
+    mp_printf(print, "GPIO P%c%02u", "ABCD"[self->id / 32], self->id % 32);
 }
 
 STATIC void pin_validate_drive(bool strength) {
@@ -84,24 +74,26 @@ STATIC mp_obj_t machine_pin_obj_init_helper(const machine_pin_obj_t *self, size_
 
     // set initial value (do this before configuring mode/pull)
     if (args[ARG_value].u_obj != mp_const_none) {
-        gpio_set_pin_level(self->id, mp_obj_is_true(args[ARG_value].u_obj));
+        mp_hal_pin_write(self->id, mp_obj_is_true(args[ARG_value].u_obj));
     }
 
     // configure mode
     if (args[ARG_mode].u_obj != mp_const_none) {
         mp_int_t mode = mp_obj_get_int(args[ARG_mode].u_obj);
         if (mode == GPIO_MODE_IN) {
-            gpio_set_pin_direction(self->id, GPIO_DIRECTION_IN);
+            mp_hal_pin_input(self->id);
         } else if (mode == GPIO_MODE_OUT) {
-            gpio_set_pin_direction(self->id, GPIO_DIRECTION_OUT);
+            mp_hal_pin_output(self->id);
+        } else if (mode == GPIO_MODE_OPEN_DRAIN) {
+            mp_hal_pin_open_drain(self->id);
         } else {
-            gpio_set_pin_direction(self->id, GPIO_DIRECTION_IN); // If no args are given, the Pin is 'input'.
+            mp_hal_pin_input(self->id); // If no args are given, the Pin is 'input'.
         }
     }
     // configure pull. Only to be used with IN mode. The function sets the pin to INPUT.
     uint32_t pull = 0;
-    mp_int_t mode = mp_obj_get_int(args[ARG_mode].u_obj);
-    if (mode == GPIO_MODE_OUT && args[ARG_pull].u_obj != mp_const_none) {
+    mp_int_t dir = mp_hal_get_pin_direction(self->id);
+    if (dir == GPIO_DIRECTION_OUT && args[ARG_pull].u_obj != mp_const_none) {
         mp_raise_ValueError(MP_ERROR_TEXT("OUT incompatible with pull"));
     } else if (args[ARG_pull].u_obj != mp_const_none) {
         pull = mp_obj_get_int(args[ARG_pull].u_obj);
@@ -143,17 +135,24 @@ mp_obj_t mp_pin_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw,
 }
 
 // fast method for getting/setting pin value
-STATIC mp_obj_t machine_pin_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+mp_obj_t machine_pin_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 0, 1, false);
     machine_pin_obj_t *self = self_in;
     if (n_args == 0) {
         // get pin
-        return MP_OBJ_NEW_SMALL_INT(gpio_get_pin_level(self->id));
+        return MP_OBJ_NEW_SMALL_INT(mp_hal_pin_read(self->id));
     } else {
         // set pin
         bool value = mp_obj_is_true(args[0]);
-        gpio_set_pin_level(self->id, value);
-
+        if (GPIO_IS_OPEN_DRAIN(self->id)) {
+            if (value == 0) {
+                mp_hal_pin_od_low(self->id);
+            } else {
+                mp_hal_pin_od_high(self->id);
+            }
+        } else {
+            mp_hal_pin_write(self->id, value);
+        }
         return mp_const_none;
     }
 }
@@ -165,7 +164,7 @@ STATIC mp_obj_t machine_pin_obj_init(size_t n_args, const mp_obj_t *args, mp_map
 MP_DEFINE_CONST_FUN_OBJ_KW(machine_pin_init_obj, 1, machine_pin_obj_init);
 
 // Pin.value([value])
-STATIC mp_obj_t machine_pin_value(size_t n_args, const mp_obj_t *args) {
+mp_obj_t machine_pin_value(size_t n_args, const mp_obj_t *args) {
     return machine_pin_call(args[0], n_args - 1, 0, args + 1);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_pin_value_obj, 1, 2, machine_pin_value);
@@ -181,9 +180,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_pin_disable_obj, machine_pin_disable);
 // Pin.low() Totem-pole (push-pull)
 STATIC mp_obj_t machine_pin_low(mp_obj_t self_in) {
     machine_pin_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    gpio_set_pin_direction(self->id, GPIO_DIRECTION_OUT);
-    gpio_set_pin_level(self->id, false);
-
+    if (GPIO_IS_OPEN_DRAIN(self->id)) {
+        mp_hal_pin_od_low(self->id);
+    } else {
+        mp_hal_pin_low(self->id);
+    }
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_pin_low_obj, machine_pin_low);
@@ -191,9 +192,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_pin_low_obj, machine_pin_low);
 // Pin.high() Totem-pole (push-pull)
 STATIC mp_obj_t machine_pin_high(mp_obj_t self_in) {
     machine_pin_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    gpio_set_pin_direction(self->id, GPIO_DIRECTION_OUT);
-    gpio_set_pin_level(self->id, true);
-
+    if (GPIO_IS_OPEN_DRAIN(self->id)) {
+        mp_hal_pin_od_high(self->id);
+    } else {
+        mp_hal_pin_high(self->id);
+    }
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_pin_high_obj, machine_pin_high);
@@ -205,18 +208,18 @@ STATIC mp_obj_t machine_pin_toggle(mp_obj_t self_in) {
     // Determine DIRECTION of PIN.
     bool pin_dir;
 
-    pin_dir = (PORT->Group[(enum gpio_port)GPIO_PORT(self->id)].DIR.reg // Get PORT#
-        & (1 << GPIO_PIN(self->id)))      // Isolate the Pin in question
-        >> GPIO_PIN(self->id);            // Shift to LSB for binary result.
-
-    if (pin_dir) {
-        // Pin is OUTPUT
-        gpio_set_pin_direction(self->id, GPIO_DIRECTION_OUT);
-        gpio_toggle_pin_level(self->id);
+    if (GPIO_IS_OPEN_DRAIN(self->id)) {
+        pin_dir = mp_hal_get_pin_direction(self->id);
+        if (pin_dir) {
+            // Pin is output, thus low, switch to high
+            mp_hal_pin_od_high(self->id);
+        } else {
+            mp_hal_pin_od_low(self->id);
+        }
     } else {
-        mp_raise_ValueError(MP_ERROR_TEXT("Cannot TOGGLE INPUT pin!\n"));
+        gpio_toggle_pin_level(self->id);
     }
-    return mp_const_true;
+    return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_pin_toggle_obj, machine_pin_toggle);
 
@@ -250,20 +253,15 @@ STATIC const mp_rom_map_elem_t machine_pin_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_disable), MP_ROM_PTR(&machine_pin_disable_obj) },
     { MP_ROM_QSTR(MP_QSTR_drive), MP_ROM_PTR(&machine_pin_drive_obj) },
 
-
-    // { MP_ROM_QSTR(MP_QSTR_irq), MP_ROM_PTR(&machine_pin_irq_obj) },
-
     // class constants
     { MP_ROM_QSTR(MP_QSTR_IN), MP_ROM_INT(GPIO_MODE_IN) },
     { MP_ROM_QSTR(MP_QSTR_OUT), MP_ROM_INT(GPIO_MODE_OUT) },
-    // { MP_ROM_QSTR(MP_QSTR_ALT), MP_ROM_INT(GPIO_MODE_ALT) },
+    { MP_ROM_QSTR(MP_QSTR_OPEN_DRAIN), MP_ROM_INT(GPIO_MODE_OPEN_DRAIN) },
     { MP_ROM_QSTR(MP_QSTR_PULL_OFF), MP_ROM_INT(GPIO_PULL_OFF) },
     { MP_ROM_QSTR(MP_QSTR_PULL_UP), MP_ROM_INT(GPIO_PULL_UP) },
     { MP_ROM_QSTR(MP_QSTR_PULL_DOWN), MP_ROM_INT(GPIO_PULL_DOWN) },
     { MP_ROM_QSTR(MP_QSTR_LOW_POWER), MP_ROM_INT(GPIO_STRENGTH_2MA) },
     { MP_ROM_QSTR(MP_QSTR_HIGH_POWER), MP_ROM_INT(GPIO_STRENGTH_8MA) },
-    // { MP_ROM_QSTR(MP_QSTR_IRQ_RISING), MP_ROM_INT(GPIO_IRQ_EDGE_RISE) },
-    // { MP_ROM_QSTR(MP_QSTR_IRQ_FALLING), MP_ROM_INT(GPIO_IRQ_EDGE_FALL) },
 };
 STATIC MP_DEFINE_CONST_DICT(machine_pin_locals_dict, machine_pin_locals_dict_table);
 
@@ -298,34 +296,6 @@ MP_DEFINE_CONST_OBJ_TYPE(
     locals_dict, &machine_pin_locals_dict
     );
 
-/*
-STATIC mp_uint_t machine_pin_irq_trigger(mp_obj_t self_in, mp_uint_t new_trigger) {
-    machine_pin_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    machine_pin_irq_obj_t *irq = MP_STATE_PORT(machine_pin_irq_obj[self->id]);
-    gpio_set_irq_enabled(self->id, GPIO_IRQ_ALL, false);
-    irq->flags = 0;
-    irq->trigger = new_trigger;
-    gpio_set_irq_enabled(self->id, new_trigger, true);
-    return 0;
-}
-
-STATIC mp_uint_t machine_pin_irq_info(mp_obj_t self_in, mp_uint_t info_type) {
-    machine_pin_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    machine_pin_irq_obj_t *irq = MP_STATE_PORT(machine_pin_irq_obj[self->id]);
-    if (info_type == MP_IRQ_INFO_FLAGS) {
-        return irq->flags;
-    } else if (info_type == MP_IRQ_INFO_TRIGGERS) {
-        return irq->trigger;
-    }
-    return 0;
-}
-
-STATIC const mp_irq_methods_t machine_pin_irq_methods = {
-    .trigger = machine_pin_irq_trigger,
-    .info = machine_pin_irq_info,
-};
-*/
-
 mp_hal_pin_obj_t mp_hal_get_pin_obj(mp_obj_t obj) {
     if (!mp_obj_is_type(obj, &machine_pin_type)) {
         mp_raise_ValueError(MP_ERROR_TEXT("expecting a Pin"));
diff --git a/ports/samd/mphalport.h b/ports/samd/mphalport.h
index b18aa2f9b4..0a1db7df0c 100644
--- a/ports/samd/mphalport.h
+++ b/ports/samd/mphalport.h
@@ -101,7 +101,7 @@ static inline void mp_hal_pin_output(mp_hal_pin_obj_t pin) {
 
 static inline void mp_hal_pin_open_drain(mp_hal_pin_obj_t pin) {
     gpio_set_pin_direction(pin, GPIO_DIRECTION_IN);
-    gpio_set_pin_level(pin, 0);
+    gpio_set_pin_pull_mode(pin, GPIO_PULL_UP);
     machine_pin_open_drain_mask[pin / 32] |= 1 << (pin % 32);
 }
 
@@ -127,10 +127,12 @@ static inline void mp_hal_pin_high(mp_hal_pin_obj_t pin) {
 
 static inline void mp_hal_pin_od_low(mp_hal_pin_obj_t pin) {
     gpio_set_pin_direction(pin, GPIO_DIRECTION_OUT);
+    gpio_set_pin_level(pin, 0);
 }
 
 static inline void mp_hal_pin_od_high(mp_hal_pin_obj_t pin) {
     gpio_set_pin_direction(pin, GPIO_DIRECTION_IN);
+    gpio_set_pin_pull_mode(pin, GPIO_PULL_UP);
 }
 
 #endif // MICROPY_INCLUDED_SAMD_MPHALPORT_H