Add hex display

hex.h

@@ -0,0 +1,17 @@
+unsigned static int const sevenseglookup[] = { 0b00111111, 0b00000110, 0b01011011, 0b01001111, 0b01100110, 0b01101101, 0b01111101, 0b00000111, 
+                                                0b01111111, 0b01100111, 0b01110111, 0b01111100, 0b01011000, 0b01011110, 0b01111001, 0b01110001 };
+
+void hex_display(int display_num, int value);
+
+// displays a hex digit accounting for an offset into the next register
+void hex_display(int display_num, int value) {
+    int address = display_num <= 3 ? HEX3_HEX0_BASE : HEX5_HEX4_BASE;
+    int offset = 0;
+
+    // make sure we're using the right offset with the given word 
+    if(display_num <= 3) offset = display_num;
+    else offset = display_num - 4;
+
+    *((int*)address) &= ~(0xFF << offset*8); // clear the two bytes of interest
+    *((int*)address) |= (sevenseglookup[value] << offset*8); // set the two bytes
+}