diff --git a/wspr.c b/wspr.c
index a25f18c..c139a58 100644
--- a/wspr.c
+++ b/wspr.c
@@ -19,9 +19,159 @@ Encoding process is in 5 steps:
 #include <string.h>
 #include <stdlib.h>
 #include <ctype.h>
+#include <dirent.h>
+#include <math.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <unistd.h>
+
 #include "wspr.h"		// wspr definitions and functions
 
 
+#define BCM2708_PERI_BASE        0x20000000
+#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
+#define PAGE_SIZE (4*1024)
+#define BLOCK_SIZE (4*1024)
+
+int  mem_fd;
+char *gpio_mem, *gpio_map;
+char *spi0_mem, *spi0_map;
+
+
+// I/O access
+volatile unsigned *gpio;
+volatile unsigned *allof7e;
+
+// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
+#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_GET *(gpio+13)  // sets   bits which are 1 ignores bits which are 0
+
+#define ACCESS(base) *(volatile int*)((int)allof7e+base-0x7e000000)
+#define SETBIT(base, bit) ACCESS(base) |= 1<<bit
+#define CLRBIT(base, bit) ACCESS(base) &= ~(1<<bit)
+#define CM_GP0CTL (0x7e101070)
+#define GPFSEL0 (0x7E200000)
+#define CM_GP0DIV (0x7e101074)
+
+
+struct GPCTL {
+    char SRC         : 4;
+    char ENAB        : 1;
+    char KILL        : 1;
+    char             : 1;
+    char BUSY        : 1;
+    char FLIP        : 1;
+    char MASH        : 2;
+    unsigned int     : 13;
+    char PASSWD      : 8;
+};
+
+void txon()
+{
+
+    allof7e = (unsigned *)mmap(
+                  NULL,
+                  0x01000000,  //len
+                  PROT_READ|PROT_WRITE,
+                  MAP_SHARED,
+                  mem_fd,
+                  0x20000000  //base
+              );
+
+    if ((int)allof7e==-1) exit(-1);
+
+    SETBIT(GPFSEL0 , 14);
+    CLRBIT(GPFSEL0 , 13);
+    CLRBIT(GPFSEL0 , 12);
+
+    struct GPCTL setupword = {6/*SRC*/, 1, 0, 0, 0, 1,0x5a};
+    ACCESS(CM_GP0CTL) = *((int*)&setupword);
+}
+
+void txoff()
+{
+    struct GPCTL setupword = {6/*SRC*/, 1, 0, 0, 0, 1,0x5a}; 
+    ACCESS(CM_GP0CTL) = *((int*)&setupword); 
+}
+
+void setfreq(long freq)
+{
+    ACCESS(CM_GP0DIV) = (0x5a << 24) + freq;
+}
+
+//
+// Set up a memory regions to access GPIO
+//
+void setup_io()
+{
+    /* open /dev/mem */
+    if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
+        printf("can't open /dev/mem \n");
+        exit (-1);
+    }
+
+    /* mmap GPIO */
+
+    // Allocate MAP block
+    if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
+        printf("allocation error \n");
+        exit (-1);
+    }
+
+    // Make sure pointer is on 4K boundary
+    if ((unsigned long)gpio_mem % PAGE_SIZE)
+        gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
+
+    // Now map it
+    gpio_map = (unsigned char *)mmap(
+                   gpio_mem,
+                   BLOCK_SIZE,
+                   PROT_READ|PROT_WRITE,
+                   MAP_SHARED|MAP_FIXED,
+                   mem_fd,
+                   GPIO_BASE
+               );
+
+    if ((long)gpio_map < 0) {
+        printf("mmap error %d\n", (int)gpio_map);
+        exit (-1);
+    }
+
+    // Always use volatile pointer!
+    gpio = (volatile unsigned *)gpio_map;
+
+
+}
+
+void setup_gpios()
+{
+   int g;
+   // Switch GPIO 7..11 to output mode
+
+    /************************************************************************\
+     * You are about to change the GPIO settings of your computer.          *
+     * Mess this up and it will stop working!                               *
+     * It might be a good idea to 'sync' before running this program        *
+     * so at least you still have your code changes written to the SD-card! *
+    \************************************************************************/
+
+    // Set GPIO pins 7-11 to output
+    for (g=7; g<=11; g++) {
+        INP_GPIO(g); // must use INP_GPIO before we can use OUT_GPIO
+        //OUT_GPIO(g);
+    }
+
+}
+
 void
 Code_msg (char usr_message[], unsigned long int *N, unsigned long int *M)
 {
@@ -278,5 +428,18 @@ int main(int argc, char *argv[])
   printf("\n");
   centre_freq = atof(argv[4]);
   sym_to_tuning_words(centre_freq, wspr_symbols, tuning_words);
+
+  /* Now we have the list of tuning words, let's transmit them
+  Note that this version doesn't check whether we are in a correct timeslot
+  */
+
+  setup_io();
+  setup_gpios();
+  txon();
+  for (i = 0; i < 162; i++) {
+    setfreq(tuning_words[i]);
+    usleep(8192/12000);
+  }
+  txoff();
   return 0;
 }