diff --git a/firmware/inc/sercom/i2c.h b/firmware/inc/sercom/i2c.h
index 4643233..c4cde8d 100644
--- a/firmware/inc/sercom/i2c.h
+++ b/firmware/inc/sercom/i2c.h
@@ -27,84 +27,23 @@
 
 #include "sercom/i2c_master.h"
 
-/**
- * We just declare our single instance here because. Very naughty
- */
-struct i2c_master_module i2c_master_instance;
-
 /**
  * I2C Write.
  *
  * address is the full write address like 0xEE
  */
-static void i2c_master_write(uint8_t address, uint8_t* data, uint16_t data_length)
-{
-  uint32_t timeout = 0;
-  struct i2c_master_packet packet = {
-    .address     = address >> 1,
-    .data_length = data_length,
-    .data        = data,
-    .ten_bit_address = false,
-    .high_speed      = false,
-    .hs_master_code  = 0x0,
-  };
-
-  while (i2c_master_write_packet_wait(&i2c_master_instance, &packet) !=
-         STATUS_OK) {
-    /* Increment timeout counter and check if timed out. */
-    if (timeout++ > 1000) {
-      break;
-    }
-  }
-}
-
+void i2c_master_write(uint8_t address, uint8_t* data, uint16_t data_length);
 
 /**
  * I2C Read.
  *
  * address is the full write address like 0xEE
  */
-static void i2c_master_read(uint8_t address, uint8_t* data, uint16_t data_length)
-{
-  uint32_t timeout = 0;
-  struct i2c_master_packet packet = {
-    .address     = address >> 1,
-    .data_length = data_length,
-    .data        = data,
-    .ten_bit_address = false,
-    .high_speed      = false,
-    .hs_master_code  = 0x0,
-  };
-
-  while (i2c_master_read_packet_wait(&i2c_master_instance, &packet) !=
-         STATUS_OK) {
-    /* Increment timeout counter and check if timed out. */
-    if (timeout++ > 1000) {
-      break;
-    }
-  }
-}
-
+void i2c_master_read(uint8_t address, uint8_t* data, uint16_t data_length);
 
 /**
  * I2C bus master.
  */
-static void i2c_init(SercomI2cm* sercom, uint32_t pad0_pinmux, uint32_t pad1_pinmux)
-{
-  struct i2c_master_config config_i2c_master;
-  i2c_master_get_config_defaults(&config_i2c_master);
-
-  /* Config */
-  config_i2c_master.buffer_timeout = 10000;
-  config_i2c_master.baud_rate = 100; /* 100 kBaud */
-
-  /* Pinmux */
-  config_i2c_master.pinmux_pad0 = pad0_pinmux;
-  config_i2c_master.pinmux_pad1 = pad1_pinmux;
-
-  /* Initialize and enable device with config. */
-  i2c_master_init(&i2c_master_instance, sercom, &config_i2c_master);
-  i2c_master_enable(&i2c_master_instance);
-}
+void i2c_init(SercomI2cm*const sercom, uint32_t pad0_pinmux, uint32_t pad1_pinmux);
 
 #endif /* I2C_H */
diff --git a/firmware/src/sercom/i2c.c b/firmware/src/sercom/i2c.c
new file mode 100644
index 0000000..96ea312
--- /dev/null
+++ b/firmware/src/sercom/i2c.c
@@ -0,0 +1,105 @@
+/*
+ * A wrapper around the samd20 i2c functions. Single master only
+ * Copyright (C) 2015  Richard Meadows <richardeoin>
+ *
+ * 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 "sercom/i2c_master.h"
+
+/**
+ * We just declare our single instance here because. Very naughty
+ */
+struct i2c_master_module i2c_master_instance;
+
+/**
+ * I2C Write.
+ *
+ * address is the full write address like 0xEE
+ */
+void i2c_master_write(uint8_t address, uint8_t* data, uint16_t data_length)
+{
+  uint32_t timeout = 0;
+  struct i2c_master_packet packet = {
+    .address     = address >> 1,
+    .data_length = data_length,
+    .data        = data,
+    .ten_bit_address = false,
+    .high_speed      = false,
+    .hs_master_code  = 0x0,
+  };
+
+  while (i2c_master_write_packet_wait(&i2c_master_instance, &packet) !=
+         STATUS_OK) {
+    /* Increment timeout counter and check if timed out. */
+    if (timeout++ > 1000) {
+      break;
+    }
+  }
+}
+
+
+/**
+ * I2C Read.
+ *
+ * address is the full write address like 0xEE
+ */
+void i2c_master_read(uint8_t address, uint8_t* data, uint16_t data_length)
+{
+  uint32_t timeout = 0;
+  struct i2c_master_packet packet = {
+    .address     = address >> 1,
+    .data_length = data_length,
+    .data        = data,
+    .ten_bit_address = false,
+    .high_speed      = false,
+    .hs_master_code  = 0x0,
+  };
+
+  while (i2c_master_read_packet_wait(&i2c_master_instance, &packet) !=
+         STATUS_OK) {
+    /* Increment timeout counter and check if timed out. */
+    if (timeout++ > 1000) {
+      break;
+    }
+  }
+}
+
+
+/**
+ * I2C bus master.
+ */
+void i2c_init(SercomI2cm*const sercom, uint32_t pad0_pinmux, uint32_t pad1_pinmux)
+{
+  struct i2c_master_config config_i2c_master;
+  i2c_master_get_config_defaults(&config_i2c_master);
+
+  /* Config */
+  config_i2c_master.buffer_timeout = 10000;
+  config_i2c_master.baud_rate = 100; /* 100 kBaud */
+
+  /* Pinmux */
+  config_i2c_master.pinmux_pad0 = pad0_pinmux;
+  config_i2c_master.pinmux_pad1 = pad1_pinmux;
+
+  /* Initialize and enable device with config. */
+  i2c_master_init(&i2c_master_instance, (Sercom*)sercom, &config_i2c_master);
+  i2c_master_enable(&i2c_master_instance);
+}