diff --git a/qt_gui/calc_main.h b/qt_gui/calc_main.h
index 3e01196..9f89bbb 100644
--- a/qt_gui/calc_main.h
+++ b/qt_gui/calc_main.h
@@ -4,13 +4,14 @@
 #define QT_GUI_CALC_MAIN_H
 
 
-#include <QMutex>
+#include <QSemaphore>
 
 extern const char KEY_MAP[20];
 
 extern int8_t NewKeyBuf[4];
 
-extern QMutex KeyMutex;
+extern QSemaphore KeysAvailable;
+extern QSemaphore LcdAvailable;
 
 extern volatile uint8_t new_key_write_i;
 extern volatile uint8_t new_key_read_i;
diff --git a/qt_gui/calculator.cpp b/qt_gui/calculator.cpp
index ee4e56b..7c3305b 100644
--- a/qt_gui/calculator.cpp
+++ b/qt_gui/calculator.cpp
@@ -5,15 +5,15 @@
 
 Calculator::Calculator(QObject *parent) :
 	QObject(parent),
-	m_lcdText("calculator initial text"),
-	m_timer(this)
+	lcd_thread(*this),
+	m_lcdText("calculator initial text")
 {
 	qDebug() << "Starting calculator thread";
 	calc_thread.start();
 	qDebug() << "calculator thread started";
-
-	QObject::connect(&m_timer, &QTimer::timeout, this, &Calculator::updateLcd);
-	m_timer.start(200);
+	qDebug() << "Starting lcd thread";
+	lcd_thread.start();
+	qDebug() << "lcd thread started";
 
 	updateLcd();
 }
@@ -21,6 +21,7 @@ Calculator::Calculator(QObject *parent) :
 Calculator::~Calculator(){
 	ExitCalcMain = 1;
 	while (!calc_thread.isFinished()); //TODO: timeout
+	while (!lcd_thread.isFinished()); //TODO: timeout
 }
 
 void Calculator::buttonClicked(const QString& in) {
@@ -35,17 +36,15 @@ void Calculator::buttonClicked(const QString& in) {
 //	qDebug() << "keycode: " << keycode;
 //	qDebug() << " row: " << row << ", col: " << col;
 	//push keycode
-	KeyMutex.lock();
 	#define INCR_NEW_KEY_I(i) i = (i + 1) & 3
 	if (!NewKeyEmpty && (new_key_write_i == new_key_read_i)){
 		printf("ERROR: key fifo full\n");
-		KeyMutex.unlock();
 		return;
 	}
 	NewKeyBuf[new_key_write_i] = keycode;
 	INCR_NEW_KEY_I(new_key_write_i);
 	NewKeyEmpty = 0;
-	KeyMutex.unlock();
+	KeysAvailable.release();
 }
 
 void Calculator::updateLcd() {
@@ -69,8 +68,24 @@ void Calculator::setLcdText(const QString &lcdText){
 }
 
 
+CalcLcdThread::CalcLcdThread(Calculator &calc) :
+	m_calc(calc)
+{
 
-void CalcThread::run() {
+}
+
+void CalcLcdThread::run(){
+	while(1){
+		if (ExitCalcMain){
+			return;
+		}
+		LcdAvailable.acquire();
+		m_calc.updateLcd();
+	}
+}
+
+
+void CalcMainThread::run() {
 	calc_main();
 }
 
diff --git a/qt_gui/calculator.h b/qt_gui/calculator.h
index 3de2395..79c11cf 100644
--- a/qt_gui/calculator.h
+++ b/qt_gui/calculator.h
@@ -4,10 +4,12 @@
 #include <QObject>
 #include <QThread>
 #include <QString>
-#include <QTimer>
 #include <QMutex>
 
-class CalcThread : public QThread
+
+class Calculator; //forward declare
+
+class CalcMainThread : public QThread //thread runs code in main.c
 {
 	Q_OBJECT
 
@@ -16,6 +18,19 @@ protected:
 };
 
 
+class CalcLcdThread : public QThread //thread just checks if we need to update lcd
+{
+	Q_OBJECT
+
+public:
+	explicit CalcLcdThread(Calculator& calc);
+protected:
+	void run() override;
+private:
+	Calculator& m_calc;
+};
+
+
 
 
 class Calculator : public QObject
@@ -39,13 +54,17 @@ public slots:
 	void updateLcd();
 
 private:
-	CalcThread calc_thread;
+	CalcMainThread calc_thread;
+	CalcLcdThread lcd_thread;
 	QString m_lcdText;
-	QTimer m_timer;
 };
 
 
 
 
 
+
+
+
+
 #endif //include guard
diff --git a/src/main.c b/src/main.c
index 226f847..227b1e5 100644
--- a/src/main.c
+++ b/src/main.c
@@ -10,7 +10,7 @@
 #include "utils.h"
 #ifdef DESKTOP
 #include <stdio.h>
-#include <QMutex>
+#include <QSemaphore>
 #else
 #include "stc15.h"
 #endif
@@ -28,7 +28,8 @@ static const char KEY_MAP[20] = {
 
 
 #ifdef DESKTOP
-QMutex KeyMutex;
+QSemaphore KeysAvailable(1);
+QSemaphore LcdAvailable(1);
 #endif
 
 int8_t NewKeyBuf[4];
@@ -147,6 +148,7 @@ int main()
 	uint8_t no_lift = 0;
 	uint8_t exp_i = 0;
 	int8_t disp_exponent;
+	NewKeyEmpty = 1; //initially empty
 #ifdef DEBUG_KEYS
 	uint8_t j = 0;
 	const uint8_t* keys;
@@ -209,7 +211,7 @@ int main()
 
 		///get new key
 #ifdef DESKTOP
-		KeyMutex.lock();
+		KeysAvailable.acquire();
 #endif
 		if (!NewKeyEmpty){
 			int8_t i_key = NewKeyBuf[new_key_read_i];
@@ -218,7 +220,6 @@ int main()
 				NewKeyEmpty = 1;
 			}
 #ifdef DESKTOP
-			KeyMutex.unlock();
 			printf("\nprocessing key %c (r=%d, w=%d, e=%d)\n",
 					KEY_MAP[i_key], new_key_read_i, new_key_write_i, NewKeyEmpty);
 			printf("entry_i=%d,exp_i=%d\n", entry_i, exp_i);
@@ -386,9 +387,6 @@ int main()
 			} //switch(KEY_MAP[i_key])
 		} else { //else for (if found new key pressed)
 			//no new key pressed
-#ifdef DESKTOP
-			KeyMutex.unlock();
-#endif
 			continue;
 		}
 
@@ -474,6 +472,7 @@ int main()
 		print_lcd();
 		printf("entry_i=%d,exp_i=%d\n", entry_i, exp_i);
 		print_entry_bufs();
+		LcdAvailable.release();
 #endif
 		//turn backlight back on
 		BACKLIGHT_ON();