diff --git a/extras/lis3mdl/lis3mdl_platform.c b/extras/lis3mdl/lis3mdl_platform.c
new file mode 100644
index 0000000..734b8ae
--- /dev/null
+++ b/extras/lis3mdl/lis3mdl_platform.c
@@ -0,0 +1,81 @@
+/**
+ * Driver for LIS3MDL 3-axes digital magnetometer to I2C or SPI.
+ *
+ * This driver is for the usage with the ESP8266 and FreeRTOS (esp-open-rtos)
+ * [https://github.com/SuperHouse/esp-open-rtos]. It is also working with ESP32
+ * and ESP-IDF [https://github.com/espressif/esp-idf.git] as well as Linux
+ * based systems using a wrapper library for ESP8266 functions.
+ *
+ * ---------------------------------------------------------------------------
+ *
+ * The BSD License (3-clause license)
+ *
+ * Copyright (c) 2017 Gunar Schorcht (https://github.com/gschorcht)
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ * contributors may be used to endorse or promote products derived from this
+ * software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * Platform file: platform specific definitions, includes and functions
+ */
+ 
+#include "lis3mdl_platform.h"
+
+// platform specific SPI functions
+
+static const spi_settings_t bus_settings = {
+    .mode         = SPI_MODE0,
+    .freq_divider = SPI_FREQ_DIV_1M,
+    .msb          = true,
+    .minimal_pins = false,
+    .endianness   = SPI_LITTLE_ENDIAN
+};
+
+bool spi_device_init (uint8_t bus, uint8_t cs)
+{
+    gpio_enable(cs, GPIO_OUTPUT);
+    gpio_write (cs, true);
+    return true;
+}
+
+size_t spi_transfer_pf(uint8_t bus, uint8_t cs, const uint8_t *mosi, uint8_t *miso, uint16_t len)
+{
+    spi_settings_t old_settings;
+
+    spi_get_settings(bus, &old_settings);
+    spi_set_settings(bus, &bus_settings);
+    gpio_write(cs, false);
+
+    size_t transfered = spi_transfer (bus, (const void*)mosi, (void*)miso, len, SPI_8BIT);
+
+    gpio_write(cs, true);
+    spi_set_settings(bus, &old_settings);
+    
+    return transfered;
+}
+
diff --git a/extras/lis3mdl/lis3mdl_platform.h b/extras/lis3mdl/lis3mdl_platform.h
index cb3792d..1c4340e 100644
--- a/extras/lis3mdl/lis3mdl_platform.h
+++ b/extras/lis3mdl/lis3mdl_platform.h
@@ -76,36 +76,10 @@
 
 #define spi_bus_init(bus,sck,miso,mosi) // not needed on ESP8266
 
-static const spi_settings_t bus_settings = {
-    .mode         = SPI_MODE0,
-    .freq_divider = SPI_FREQ_DIV_1M,
-    .msb          = true,
-    .minimal_pins = false,
-    .endianness   = SPI_LITTLE_ENDIAN
-};
-
-inline static bool spi_device_init (uint8_t bus, uint8_t cs)
-{
-    gpio_enable(cs, GPIO_OUTPUT);
-    gpio_write (cs, true);
-    return true;
-}
-
-inline static size_t spi_transfer_pf(uint8_t bus, uint8_t cs, const uint8_t *mosi, uint8_t *miso, uint16_t len)
-{
-    spi_settings_t old_settings;
-
-    spi_get_settings(bus, &old_settings);
-    spi_set_settings(bus, &bus_settings);
-    gpio_write(cs, false);
-
-    size_t transfered = spi_transfer (bus, (const void*)mosi, (void*)miso, len, SPI_8BIT);
-
-    gpio_write(cs, true);
-    spi_set_settings(bus, &old_settings);
-    
-    return transfered;
-}
+extern bool   spi_device_init (uint8_t bus, uint8_t cs);
+extern size_t spi_transfer_pf (uint8_t bus, uint8_t cs,
+                               const uint8_t *mosi, uint8_t *miso,
+                               uint16_t len);
 
 #endif // ESP_OPEN_RTOS