diff --git a/src/energenie/drv/gpio_arduino.c b/src/energenie/drv/gpio_arduino.c
new file mode 100644
index 0000000..589e77c
--- /dev/null
+++ b/src/energenie/drv/gpio_arduino.c
@@ -0,0 +1,98 @@
+/* gpio_arduino.c  D.J.Whale  04/04/2016
+ * 
+ * A very simple interface to the GPIO port on the Arduino.
+ *
+ * Arduino internally uses the 'wiring' library, but experiments have shown
+ * that it is really slow.
+ *
+ * (see blog by skpang)
+ *
+ * So this module uses direct register writes, and provides a placeholder for
+ * compile-time selection of bitmasks and bitpatterns to support more Arduino
+ * boards in the future.
+ */
+
+//TODO GPIO_SIMULATED can be replaced with gpio_sim.c in future
+
+/***** INCLUDES *****/
+
+//#include <stdio.h>
+//#include <stdlib.h>
+//#include <stdint.h>
+//#include <fcntl.h>
+//#include <sys/mman.h>
+//#include <unistd.h>
+//#include <time.h>
+
+//#include "gpio.h"
+
+
+/***** CONFIGURATION *****/
+
+/* uncomment to make this a simulated driver */
+//#define GPIO_SIMULATED
+
+
+/***** CONSTANTS *****/
+
+
+/***** VARIABLES *****/
+
+/****** MACROS *****/
+
+//#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
+//#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
+//#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
+
+//#define GPIO_SET *(gpio+7)  // sets   bits which are 1 ignores bits which are 0
+//#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
+
+//#define GPIO_READ(g) ((*(gpio+13)&(1<<g)) != 0)
+
+//#define GPIO_HIGH(g) GPIO_SET = (1<<(g))
+//#define GPIO_LOW(g)  GPIO_CLR = (1<<(g))
+
+
+void gpio_init()
+{
+  //TODO
+}
+
+
+void gpio_setin(int g)
+{
+  //TODO
+}
+
+
+void gpio_setout(int g)
+{
+  //TODO
+}
+
+
+void gpio_high(int g)
+{
+  //TODO
+}
+
+
+void gpio_low(int g)
+{
+  //TODO
+}
+
+
+void gpio_write(int g, int v)
+{
+  //TODO
+}
+
+
+int  gpio_read(int g)
+{
+  //TODO
+}
+
+
+/***** END OF FILE *****/
diff --git a/src/energenie/drv/gpio_rpi.c b/src/energenie/drv/gpio_rpi.c
index 7d9a144..ce0cd6e 100644
--- a/src/energenie/drv/gpio_rpi.c
+++ b/src/energenie/drv/gpio_rpi.c
@@ -16,12 +16,6 @@
 #include "gpio.h"
 
 
-/***** CONFIGURATION *****/
-
-/* uncomment to make this a simulated driver */
-//#define GPIO_SIMULATED
-
-
 /***** CONSTANTS *****/
 
 #define BCM2708_PERI_BASE        0x20000000
@@ -57,8 +51,6 @@
 
 void gpio_init()
 {
-#ifndef GPIO_SIMULATED
-
    uint32_t peri_base = BCM2708_PERI_BASE; /* default if device tree not found */
    uint32_t gpio_base;
    FILE* fp;
@@ -106,55 +98,37 @@
 
    // Always use volatile pointer!
    gpio = (volatile unsigned *)gpio_map;
-#endif
 }
 
 
 void gpio_setin(int g)
 {
-#ifndef GPIO_SIMULATED
   INP_GPIO(g);
-#else
-  printf("gpio:in:%d\n", g);
-#endif
 }
 
 
 void gpio_setout(int g)
 {
-#ifndef GPIO_SIMULATED
   /* always INP_GPIO before OUT_GPIO */
   //INP_GPIO(g); #### this causes glitching
   OUT_GPIO(g);
-#else
-  printf("gpio:out:%d\n", g);
-#endif
 }
 
 
 void gpio_high(int g)
 {
-#ifndef GPIO_SIMULATED
   GPIO_HIGH(g);
-#else
-  printf("gpio:high:%d\n", g);
-#endif
 }
 
 
 void gpio_low(int g)
 {
-#ifndef GPIO_SIMULATED
   GPIO_LOW(g);
-#else
-  printf("gpio:low:%d\n", g);
-#endif
 }
 
 
 void gpio_write(int g, int v)
 {
-#ifndef GPIO_SIMULATED
   if (v != 0)
   {
     GPIO_HIGH(g);
@@ -163,19 +137,12 @@
   {
     GPIO_LOW(g);
   }
-#else
-  printf("gpio:write:%d=%d\n", g, v);
-#endif
 }
 
 
-int  gpio_read(int g)
+int gpio_read(int g)
 {
-#ifndef GPIO_SIMULATED
   return GPIO_READ(g);
-#else
-  return 0; /* always low in simulation */
-#endif
 }
 
 
diff --git a/src/energenie/drv/gpio_sim.c b/src/energenie/drv/gpio_sim.c
new file mode 100644
index 0000000..de2c2d7
--- /dev/null
+++ b/src/energenie/drv/gpio_sim.c
@@ -0,0 +1,82 @@
+/* gpio_sim.c  D.J.Whale  04/04/2016
+ * 
+ * A very simple interface to a simulated GPIO port with no platform dependencies.
+ */
+
+/***** INCLUDES *****/
+
+#include <stdio.h>
+//#include <stdlib.h>
+
+#include "gpio.h"
+
+
+/***** CONFIGURATION *****/
+
+
+/***** CONSTANTS *****/
+
+
+/***** VARIABLES *****/
+
+
+/****** MACROS *****/
+
+//#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
+//#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
+//#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
+
+//#define GPIO_SET *(gpio+7)  // sets   bits which are 1 ignores bits which are 0
+//#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
+
+//#define GPIO_READ(g) ((*(gpio+13)&(1<<g)) != 0)
+
+//#define GPIO_HIGH(g) GPIO_SET = (1<<(g))
+//#define GPIO_LOW(g)  GPIO_CLR = (1<<(g))
+
+
+void gpio_init()
+{
+  // Nothing to do
+}
+
+
+void gpio_setin(int g)
+{
+    printf("gpio:in:%d\n", g);
+}
+
+
+void gpio_setout(int g)
+{
+    printf("gpio:out:%d\n", g);
+}
+
+
+void gpio_high(int g)
+{
+    printf("gpio:high:%d\n", g);
+}
+
+
+void gpio_low(int g)
+{
+    printf("gpio:low:%d\n", g);
+}
+
+
+void gpio_write(int g, int v)
+{
+    printf("gpio:write:%d=%d\n", g, v);
+}
+
+
+int gpio_read(int g)
+{
+    //TODO add a console interface to allow GPIO reads to be injected
+    //either from keyboard, or from a script file
+    return 0; /* always low in simulation */
+}
+
+
+/***** END OF FILE *****/