diff --git a/ports/atmel-samd/Makefile b/ports/atmel-samd/Makefile
index e85a11b5701b1..eb25c1aa302c1 100644
--- a/ports/atmel-samd/Makefile
+++ b/ports/atmel-samd/Makefile
@@ -227,6 +227,7 @@ SRC_ASF := $(addprefix asf4/$(CHIP_FAMILY)/, $(SRC_ASF))
 
 SRC_C = \
 	audio_dma.c \
+	board_busses.c \
 	background.c \
 	clocks.c \
 	$(CHIP_FAMILY)_clocks.c \
diff --git a/ports/atmel-samd/board_busses.c b/ports/atmel-samd/board_busses.c
new file mode 100644
index 0000000000000..0dc95a32c70a0
--- /dev/null
+++ b/ports/atmel-samd/board_busses.c
@@ -0,0 +1,62 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
+ *
+ * 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 "shared-bindings/busio/I2C.h"
+#include "shared-bindings/microcontroller/Pin.h"
+#include "mpconfigboard.h"
+#include "pins.h"
+#include "py/runtime.h"
+
+
+
+#if !defined(DEFAULT_I2C_BUS_SDA) || !defined(DEFAULT_I2C_BUS_SCL)
+
+    STATIC mp_obj_t board_i2c(void) {
+        //board_i2c_obj = NULL;
+        mp_raise_NotImplementedError("No default I2C bus");
+        return NULL;
+    }
+
+#else
+    STATIC mp_obj_t i2c_singleton = NULL;
+
+    STATIC mp_obj_t board_i2c(void) {
+
+        if (i2c_singleton == NULL) {
+            busio_i2c_obj_t *self = m_new_obj(busio_i2c_obj_t);
+            self->base.type = &busio_i2c_type;
+
+            assert_pin_free(DEFAULT_I2C_BUS_SDA);
+            assert_pin_free(DEFAULT_I2C_BUS_SCL);
+            common_hal_busio_i2c_construct(self, DEFAULT_I2C_BUS_SCL, DEFAULT_I2C_BUS_SDA, 400000, 0);
+            i2c_singleton = (mp_obj_t)self;
+        }
+        return i2c_singleton;
+
+    }
+#endif
+
+MP_DEFINE_CONST_FUN_OBJ_0(board_i2c_obj, board_i2c);
diff --git a/ports/atmel-samd/board_busses.h b/ports/atmel-samd/board_busses.h
new file mode 100644
index 0000000000000..e872e4902bb67
--- /dev/null
+++ b/ports/atmel-samd/board_busses.h
@@ -0,0 +1,33 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
+ *
+ * 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.
+ */
+
+#ifndef MICROPY_INCLUDED_ATMEL_SAMD_BOARD_BUSSES_H
+#define MICROPY_INCLUDED_ATMEL_SAMD_BOARD_BUSSES_H
+
+void board_i2c(void);
+extern mp_obj_fun_builtin_fixed_t board_i2c_obj;
+
+#endif  // MICROPY_INCLUDED_ATMEL_SAMD_BOARD_BUSSES_H
diff --git a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.h b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.h
index 6eeddb36c72a2..11e01b6c601f4 100644
--- a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.h
+++ b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.h
@@ -14,3 +14,6 @@
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/arduino_zero/pins.c b/ports/atmel-samd/boards/arduino_zero/pins.c
index 8b28c0fc22b3b..74cff5ae86f2f 100644
--- a/ports/atmel-samd/boards/arduino_zero/pins.c
+++ b/ports/atmel-samd/boards/arduino_zero/pins.c
@@ -1,6 +1,8 @@
 #include "shared-bindings/board/__init__.h"
 
 #include "samd21_pins.h"
+#include "board_busses.h"
+
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -30,5 +32,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SCK), MP_ROM_PTR(&pin_PB11) },
     { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_PB10) },
     { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_PA12) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/circuitplayground_express/mpconfigboard.h b/ports/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
index 73d45f2cf849f..6ea0d93602178 100644
--- a/ports/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
@@ -58,3 +58,6 @@
 
 // Explanation of how a user got into safe mode.
 #define BOARD_USER_SAFE_MODE_ACTION "pressing both buttons at start up"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PB03)
+#define DEFAULT_I2C_BUS_SDA (&pin_PB02)
diff --git a/ports/atmel-samd/boards/circuitplayground_express/pins.c b/ports/atmel-samd/boards/circuitplayground_express/pins.c
index aecd7f416a2dd..c0545fd7c00a3 100644
--- a/ports/atmel-samd/boards/circuitplayground_express/pins.c
+++ b/ports/atmel-samd/boards/circuitplayground_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -56,5 +57,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SCK),  MP_ROM_PTR(&pin_PA05) },
     { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_PA07) },
     { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
index 8802d39d99d91..dc9aabf17cf3e 100644
--- a/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
@@ -12,3 +12,6 @@
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA22)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA23)
diff --git a/ports/atmel-samd/boards/feather_m0_adalogger/pins.c b/ports/atmel-samd/boards/feather_m0_adalogger/pins.c
index a229b6bab1814..cf4160d72369e 100644
--- a/ports/atmel-samd/boards/feather_m0_adalogger/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_adalogger/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -30,5 +31,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA19) },
     { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA17) },
     { MP_ROM_QSTR(MP_QSTR_RED_LED), MP_ROM_PTR(&pin_PA17) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_basic/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
index 04cbc4ff8aa46..dff82912ece6e 100644
--- a/ports/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
@@ -13,3 +13,6 @@
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/feather_m0_basic/pins.c b/ports/atmel-samd/boards/feather_m0_basic/pins.c
index c9119e77bc880..2916df7a1cf57 100644
--- a/ports/atmel-samd/boards/feather_m0_basic/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_basic/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -23,5 +24,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D11), MP_ROM_PTR(&pin_PA16) },
     { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA19) },
     { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA17) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
index c85f553ba9d71..4435412dfa7ff 100644
--- a/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
@@ -48,3 +48,6 @@
 #include "external_flash/external_flash.h"
 
 #define BOARD_HAS_CRYSTAL 1
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/feather_m0_express/pins.c b/ports/atmel-samd/boards/feather_m0_express/pins.c
index c5c70ee5dcdd5..740be2cbd6e92 100644
--- a/ports/atmel-samd/boards/feather_m0_express/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -24,5 +25,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA19) },
     { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA17) },
     { MP_ROM_QSTR(MP_QSTR_NEOPIXEL), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_rfm69/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_rfm69/mpconfigboard.h
index 33445940e65aa..1a3fa72f2101c 100644
--- a/ports/atmel-samd/boards/feather_m0_rfm69/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_rfm69/mpconfigboard.h
@@ -13,3 +13,8 @@
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
+
+// https://learn.adafruit.com/assets/46254
+// https://learn.adafruit.com/assets/46255
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/feather_m0_rfm69/pins.c b/ports/atmel-samd/boards/feather_m0_rfm69/pins.c
index eb5f531e361b6..6a35c33d494e9 100644
--- a/ports/atmel-samd/boards/feather_m0_rfm69/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_rfm69/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -26,5 +27,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_RFM69_D0), MP_ROM_PTR(&pin_PA09) },
     { MP_ROM_QSTR(MP_QSTR_RFM69_RST), MP_ROM_PTR(&pin_PA08) },
     { MP_ROM_QSTR(MP_QSTR_RFM69_CS), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_rfm9x/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_rfm9x/mpconfigboard.h
index a2563cc9f1202..cac39ee84636c 100644
--- a/ports/atmel-samd/boards/feather_m0_rfm9x/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_rfm9x/mpconfigboard.h
@@ -13,3 +13,9 @@
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
+
+// https://learn.adafruit.com/assets/46254
+// https://learn.adafruit.com/assets/46255
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
+
diff --git a/ports/atmel-samd/boards/feather_m0_rfm9x/pins.c b/ports/atmel-samd/boards/feather_m0_rfm9x/pins.c
index 2e5d0a8e68cc1..bf4b3b347d442 100644
--- a/ports/atmel-samd/boards/feather_m0_rfm9x/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_rfm9x/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -26,5 +27,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_RFM9X_D0), MP_ROM_PTR(&pin_PA09) },
     { MP_ROM_QSTR(MP_QSTR_RFM9X_RST), MP_ROM_PTR(&pin_PA08) },
     { MP_ROM_QSTR(MP_QSTR_RFM9X_CS), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m0_supersized/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_supersized/mpconfigboard.h
index 5bc74d5a747a0..037d9b9922e62 100644
--- a/ports/atmel-samd/boards/feather_m0_supersized/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_supersized/mpconfigboard.h
@@ -47,3 +47,6 @@
 #define EXTERNAL_FLASH_DEVICES S25FL064L
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/feather_m0_supersized/pins.c b/ports/atmel-samd/boards/feather_m0_supersized/pins.c
index c5c70ee5dcdd5..740be2cbd6e92 100644
--- a/ports/atmel-samd/boards/feather_m0_supersized/pins.c
+++ b/ports/atmel-samd/boards/feather_m0_supersized/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -24,5 +25,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA19) },
     { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA17) },
     { MP_ROM_QSTR(MP_QSTR_NEOPIXEL), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/feather_m4_express/mpconfigboard.h b/ports/atmel-samd/boards/feather_m4_express/mpconfigboard.h
index 6e1022256247f..48c63454e509f 100644
--- a/ports/atmel-samd/boards/feather_m4_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m4_express/mpconfigboard.h
@@ -31,3 +31,6 @@
 #define EXTERNAL_FLASH_QSPI_DUAL
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA13)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA12)
diff --git a/ports/atmel-samd/boards/feather_m4_express/pins.c b/ports/atmel-samd/boards/feather_m4_express/pins.c
index c161e736edc15..2fa5fa1b56fd5 100644
--- a/ports/atmel-samd/boards/feather_m4_express/pins.c
+++ b/ports/atmel-samd/boards/feather_m4_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -26,5 +27,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA22) },
     { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA23) },
     { MP_ROM_QSTR(MP_QSTR_NEOPIXEL), MP_ROM_PTR(&pin_PB23) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/gemma_m0/mpconfigboard.h b/ports/atmel-samd/boards/gemma_m0/mpconfigboard.h
index 45a6a694e9430..2527b9d0691dd 100644
--- a/ports/atmel-samd/boards/gemma_m0/mpconfigboard.h
+++ b/ports/atmel-samd/boards/gemma_m0/mpconfigboard.h
@@ -12,6 +12,9 @@
 
 #define CIRCUITPY_INTERNAL_NVM_SIZE 0
 
+#define DEFAULT_I2C_BUS_SCL (&pin_PA05)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA04)
+
 #include "internal_flash.h"
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/ports/atmel-samd/boards/gemma_m0/pins.c b/ports/atmel-samd/boards/gemma_m0/pins.c
index 5d3bedca0e40a..6d9d2ad759aac 100644
--- a/ports/atmel-samd/boards/gemma_m0/pins.c
+++ b/ports/atmel-samd/boards/gemma_m0/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A1),  MP_ROM_PTR(&pin_PA05) }, // pad 1
@@ -19,5 +20,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PA00) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK),  MP_ROM_PTR(&pin_PA01) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/itsybitsy_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/itsybitsy_m0_express/mpconfigboard.h
index a7ecd27ea8b60..7b0280acb34ad 100644
--- a/ports/atmel-samd/boards/itsybitsy_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/itsybitsy_m0_express/mpconfigboard.h
@@ -46,3 +46,6 @@
                                GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/itsybitsy_m0_express/pins.c b/ports/atmel-samd/boards/itsybitsy_m0_express/pins.c
index b70bb6a76c6e5..8eec4ca224ce6 100644
--- a/ports/atmel-samd/boards/itsybitsy_m0_express/pins.c
+++ b/ports/atmel-samd/boards/itsybitsy_m0_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D0), MP_ROM_PTR(&pin_PA11) },
@@ -38,5 +39,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PA01) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK), MP_ROM_PTR(&pin_PA00) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/itsybitsy_m4_express/mpconfigboard.h b/ports/atmel-samd/boards/itsybitsy_m4_express/mpconfigboard.h
index 95c542a43eb72..e8335ef3f86e1 100644
--- a/ports/atmel-samd/boards/itsybitsy_m4_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/itsybitsy_m4_express/mpconfigboard.h
@@ -31,3 +31,6 @@
 #define EXTERNAL_FLASH_DEVICES GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA13)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA12)
diff --git a/ports/atmel-samd/boards/itsybitsy_m4_express/pins.c b/ports/atmel-samd/boards/itsybitsy_m4_express/pins.c
index 11aeda9c67859..490922a46a8d5 100644
--- a/ports/atmel-samd/boards/itsybitsy_m4_express/pins.c
+++ b/ports/atmel-samd/boards/itsybitsy_m4_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd51_pins.h"
+#include "board_busses.h"
 
 // This mapping only includes functional names because pins broken
 // out on connectors are labeled with their MCU name available from
@@ -35,5 +36,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PB03) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK), MP_ROM_PTR(&pin_PB02) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
index e635acd5934b3..9b8b0ab88c546 100644
--- a/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
@@ -49,3 +49,6 @@
 #include "external_flash/external_flash.h"
 
 #define BOARD_HAS_CRYSTAL 1
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
diff --git a/ports/atmel-samd/boards/metro_m0_express/pins.c b/ports/atmel-samd/boards/metro_m0_express/pins.c
index 58510faabb62b..32f3f875c4a4a 100644
--- a/ports/atmel-samd/boards/metro_m0_express/pins.c
+++ b/ports/atmel-samd/boards/metro_m0_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
@@ -29,5 +30,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SCK),  MP_ROM_PTR(&pin_PB11) },
     { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_PB10) },
     { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_PA12) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/metro_m4_express/mpconfigboard.h b/ports/atmel-samd/boards/metro_m4_express/mpconfigboard.h
index 701203771780c..0d93ed700e45f 100644
--- a/ports/atmel-samd/boards/metro_m4_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/metro_m4_express/mpconfigboard.h
@@ -32,3 +32,6 @@
 #define EXTERNAL_FLASH_DEVICES S25FL116K, S25FL216K, GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PB03)
+#define DEFAULT_I2C_BUS_SDA (&pin_PB02)
diff --git a/ports/atmel-samd/boards/metro_m4_express/pins.c b/ports/atmel-samd/boards/metro_m4_express/pins.c
index 32ecdf4923a09..1d24a0f2f2afc 100644
--- a/ports/atmel-samd/boards/metro_m4_express/pins.c
+++ b/ports/atmel-samd/boards/metro_m4_express/pins.c
@@ -1,4 +1,5 @@
 #include "samd51_pins.h"
+#include "board_busses.h"
 
 // This mapping only includes functional names because pins broken
 // out on connectors are labeled with their MCU name available from
@@ -41,5 +42,6 @@ STATIC const mp_map_elem_t board_global_dict_table[] = {
 
     { MP_OBJ_NEW_QSTR(MP_QSTR_LED_RX), (mp_obj_t)&pin_PB06 },
     { MP_OBJ_NEW_QSTR(MP_QSTR_LED_TX), (mp_obj_t)&pin_PA27 },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/metro_m4_express_revb/mpconfigboard.h b/ports/atmel-samd/boards/metro_m4_express_revb/mpconfigboard.h
index 206d85465e043..8f3c0cd0e0213 100644
--- a/ports/atmel-samd/boards/metro_m4_express_revb/mpconfigboard.h
+++ b/ports/atmel-samd/boards/metro_m4_express_revb/mpconfigboard.h
@@ -60,3 +60,6 @@
                                GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PB03)
+#define DEFAULT_I2C_BUS_SDA (&pin_PB02)
diff --git a/ports/atmel-samd/boards/metro_m4_express_revb/pins.c b/ports/atmel-samd/boards/metro_m4_express_revb/pins.c
index a18906f73d4c1..5e6e719aceafa 100644
--- a/ports/atmel-samd/boards/metro_m4_express_revb/pins.c
+++ b/ports/atmel-samd/boards/metro_m4_express_revb/pins.c
@@ -1,4 +1,5 @@
 #include "samd51_pins.h"
+#include "board_busses.h"
 
 // This mapping only includes functional names because pins broken
 // out on connectors are labeled with their MCU name available from
@@ -40,5 +41,6 @@ STATIC const mp_map_elem_t board_global_dict_table[] = {
 
     { MP_OBJ_NEW_QSTR(MP_QSTR_LED_RX), (mp_obj_t)&pin_PB06 },
     { MP_OBJ_NEW_QSTR(MP_QSTR_LED_TX), (mp_obj_t)&pin_PA27 },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/pirkey_m0/pins.c b/ports/atmel-samd/boards/pirkey_m0/pins.c
index a1b7db85c89b0..dac668795569a 100644
--- a/ports/atmel-samd/boards/pirkey_m0/pins.c
+++ b/ports/atmel-samd/boards/pirkey_m0/pins.c
@@ -1,9 +1,11 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_REMOTEIN),   MP_ROM_PTR(&pin_PA28) },
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PA00) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK),  MP_ROM_PTR(&pin_PA01) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/trinket_m0/mpconfigboard.h b/ports/atmel-samd/boards/trinket_m0/mpconfigboard.h
index 92a14ba15a969..d2872d1425b8c 100644
--- a/ports/atmel-samd/boards/trinket_m0/mpconfigboard.h
+++ b/ports/atmel-samd/boards/trinket_m0/mpconfigboard.h
@@ -56,3 +56,6 @@
 #define IGNORE_PIN_PB30     1
 #define IGNORE_PIN_PB31     1
 #define IGNORE_PIN_PB00     1
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA09)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA08)
diff --git a/ports/atmel-samd/boards/trinket_m0/pins.c b/ports/atmel-samd/boards/trinket_m0/pins.c
index ac5898600943d..74d03def296d4 100644
--- a/ports/atmel-samd/boards/trinket_m0/pins.c
+++ b/ports/atmel-samd/boards/trinket_m0/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D0), MP_ROM_PTR(&pin_PA08) },
@@ -27,5 +28,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PA00) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK), MP_ROM_PTR(&pin_PA01) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/trinket_m0_haxpress/mpconfigboard.h b/ports/atmel-samd/boards/trinket_m0_haxpress/mpconfigboard.h
index ea45c1f8b88f1..9142a7d7a708d 100644
--- a/ports/atmel-samd/boards/trinket_m0_haxpress/mpconfigboard.h
+++ b/ports/atmel-samd/boards/trinket_m0_haxpress/mpconfigboard.h
@@ -54,3 +54,6 @@
 #define EXTERNAL_FLASH_DEVICES W25Q32BV
 
 #include "external_flash/external_flash.h"
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA09)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA08)
diff --git a/ports/atmel-samd/boards/trinket_m0_haxpress/pins.c b/ports/atmel-samd/boards/trinket_m0_haxpress/pins.c
index ac5898600943d..74d03def296d4 100644
--- a/ports/atmel-samd/boards/trinket_m0_haxpress/pins.c
+++ b/ports/atmel-samd/boards/trinket_m0_haxpress/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_D0), MP_ROM_PTR(&pin_PA08) },
@@ -27,5 +28,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_APA102_MOSI), MP_ROM_PTR(&pin_PA00) },
     { MP_ROM_QSTR(MP_QSTR_APA102_SCK), MP_ROM_PTR(&pin_PA01) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/boards/ugame10/pins.c b/ports/atmel-samd/boards/ugame10/pins.c
index af516a401d9fc..2af55f6da75b8 100644
--- a/ports/atmel-samd/boards/ugame10/pins.c
+++ b/ports/atmel-samd/boards/ugame10/pins.c
@@ -1,4 +1,5 @@
 #include "samd21_pins.h"
+#include "board_busses.h"
 
 STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_X), MP_ROM_PTR(&pin_PA00) },
@@ -23,5 +24,6 @@ STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_B), MP_ROM_PTR(&pin_PA14) },
     { MP_ROM_QSTR(MP_QSTR_C), MP_ROM_PTR(&pin_PA15) },
     { MP_ROM_QSTR(MP_QSTR_D), MP_ROM_PTR(&pin_PA28) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);