diff --git a/src/calc.c b/src/calc.c
index 8b55d08..9bae55b 100644
--- a/src/calc.c
+++ b/src/calc.c
@@ -5,6 +5,7 @@
  */
 
 #include "decn/decn.h"
+#include "utils.h"
 
 #define STACK_SIZE 4 //must be a power of 2
 
@@ -52,6 +53,8 @@ static void do_binary_op(void (*f_ptr)(dec80*, const dec80*)){
 }
 
 void process_cmd(char cmd){
+	//turn off backlight before start of processing
+	backlight_off();
 	//process cmd
 	switch(cmd){
 		//////////
diff --git a/src/main.c b/src/main.c
index 264066c..241aa6d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -29,8 +29,8 @@ volatile uint8_t NewKeyEmpty;
 #define INCR_NEW_KEY_I(i) i = (i + 1) & 3
 
 volatile uint8_t SecCount;
-void timer0_isr() __interrupt 1 __using 1
 //#define TRACK_TIME
+void timer0_isr() SDCC_ISR(1,1)
 {
 #ifdef TRACK_TIME
 	static uint8_t count = 0;
@@ -71,6 +71,10 @@ void timer0_isr() __interrupt 1 __using 1
 }
 
 
+#ifdef DESKTOP
+void Timer0Init(void) { }
+static void latch_on(void){ }
+#else
 // Call timer0_isr() 200/sec: 5 ms period
 // Initialize the timer count so that it overflows after 0.01 sec
 // THTL = 0x10000 - FOSC / 200 = 0x10000 - 115830 = 7621 = 0x1DC5
@@ -87,6 +91,7 @@ void Timer0Init(void)
 	EA  = 1;		// Enable global interrupt
 }
 
+#endif //!DESKTOP
 
 
 char Buf[DECN_BUF_SIZE];
@@ -118,6 +123,8 @@ int main()
 #ifdef DEBUG_UPTIME
 	uint32_t i;
 #endif
+
+	latch_on();
 	Timer0Init(); // display refresh & switch read
 	LCD_Open();
 	KeyInit();
@@ -127,6 +134,7 @@ int main()
 	P3_2 = 1; //latch on
 	P3M1 &= ~(0x4);
 	P3M0 |= (0x4);
+	BACKLIGHT_ON(); //turn on led backlight
 
 #ifdef DEBUG_UPTIME
 	i = 0;
@@ -134,6 +142,11 @@ int main()
 	// LOOP
 	while (1)
 	{
+		//turn off?
+		if (Keys[0] == 8 && Keys[4] == 8){
+			TURN_OFF();
+		}
+
 		LCD_GoTo(0,0);
 #ifdef DEBUG_UPTIME
 		u32str(i++, Buf, 10);
@@ -155,11 +168,6 @@ int main()
 		for (key_i = 0; key_i < 5; key_i++){
 			LCD_OutNibble(keys[key_i]);
 		}
-		//turn off?
-		if (keys[0] == 8 && keys[4] == 8){
-			P3_2 = 0;
-		}
-
 		TERMIO_PutChar(',');
 		//counter
 		if (SecCount == 0){
@@ -181,7 +189,6 @@ int main()
 			if (new_key_read_i == new_key_write_i){
 				NewKeyEmpty = 1;
 			}
-
 #ifdef DEBUG_KEYS
 			LCD_GoTo(1,j);
 #endif
@@ -374,6 +381,8 @@ int main()
 			TERMIO_PutChar(ExpBuf[0] + '0');
 		}
 		LCD_ClearToEnd(1);
+		//turn backlight back on
+		BACKLIGHT_ON();
 	} //while (1)
 }
 /* ------------------------------------------------------------------------- */
diff --git a/src/utils.c b/src/utils.c
index aa38cc5..3b7f946 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include "stc15.h"
 #include "utils.h"
 
 #ifdef DESKTOP
@@ -11,6 +12,8 @@ void _delay_us(uint8_t us)
 	//TODO:
 }
 #endif
+void backlight_off(void){ }
+#else //!DESKTOP
 void _delay_ms(uint8_t ms)
 {
 	// delay function, tuned for 11.583 MHz clock
@@ -49,6 +52,12 @@ void _delay_us(uint8_t us)
 }
 #endif
 
+void backlight_off(void){
+	P3_4 = 1;
+}
+
+#endif //ifdef desktop
+
 char* u32str(uint32_t x, char* buf, uint8_t base)
 {
 	int i = 0, j;
diff --git a/src/utils.h b/src/utils.h
index 0c4d1fc..af958b9 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -18,6 +18,7 @@ void _delay_us(uint8_t us);
 #define _delay_us(x) _delay_ms(1)
 #endif
 
+void backlight_off(void);
 
 char* u32str(uint32_t x, char* buf, uint8_t base);
 
@@ -30,5 +31,18 @@ char* u32str(uint32_t x, char* buf, uint8_t base);
 #define DESKTOP
 #endif
 
+#if defined(DESKTOP) || defined(IS_ECLIPSE)
+#define __xdata
+#define __sfr
+#define __at uint8_t*
+#define SDCC_ISR(isr, reg)
+#define BACKLIGHT_ON()
+#define TURN_OFF()
+#else
+#define SDCC_ISR(isr, reg) __interrupt (isr) __using (reg)
+#define BACKLIGHT_ON()  P3_4 = 0
+#define TURN_OFF() P3_2 = 0
+#endif
+
 #endif /* SRC_UTILS_H_ */