diff --git a/sound-driver/Makefile b/sound-driver/Makefile
index 0f70fcb..ad4569c 100644
--- a/sound-driver/Makefile
+++ b/sound-driver/Makefile
@@ -7,11 +7,11 @@ MCU=msp430g2553
 CFLAGS=-Wall -mmcu=$(MCU) -std=gnu99 -I $(TOOLCHAIN_PREFIX)/include -O1 -g0
 
 # for debugging
-#CFLAGS+= -g3 -ggdb -gdwarf-2
+CFLAGS+= -g3 -ggdb -gdwarf-2
 
 LDFLAGS=-mmcu=$(MCU) -L $(TOOLCHAIN_PREFIX)/include
 
-$(ARTIFACT).elf:	main.o
+$(ARTIFACT).elf:	main.o scheduler.o
 	$(CC) -o $@ $(LDFLAGS) $^
 	$(OBJDUMP) -D $(ARTIFACT).elf > $(ARTIFACT).txt
 
diff --git a/sound-driver/firmware.gdb b/sound-driver/firmware.gdb
new file mode 100644
index 0000000..6312fd6
--- /dev/null
+++ b/sound-driver/firmware.gdb
@@ -0,0 +1,2 @@
+target remote localhost:2000
+file firmware.elf
diff --git a/sound-driver/main.c b/sound-driver/main.c
index aa8c0f1..8c8e13a 100644
--- a/sound-driver/main.c
+++ b/sound-driver/main.c
@@ -2,12 +2,14 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#include "notes.h"
+#include "scheduler.h"
+
 
 #define ADDR_DATA_REG P2OUT
 #define BUS_CTRL_REG P1OUT
-#define BC1 BIT0
+#define BC1 BIT3
 #define BDIR BIT1
-#define _CS BIT3
 
 #define R0 0
 #define R1 1
@@ -24,12 +26,6 @@
 #define R14 014
 #define R15 015
 
-inline static void BUS_OP_ENABLE_CS() {
-  BUS_CTRL_REG &= ~_CS;
-}
-inline static void BUS_OP_DISABLE_CS() {
-  BUS_CTRL_REG |= _CS;
-}
 inline static void BUS_OP_NACT() {
   BUS_CTRL_REG &= ~(BDIR | BC1);
 }
@@ -62,9 +58,6 @@ asm volatile (
 static void writePSG(uint8_t address, uint8_t data) {
   // according to "State Timing" (p. 15) of datasheet
 
-  // select chip
-  //BUS_OP_ENABLE_CS();
-
   // put bus into inactive state
   BUS_OP_NACT();
 
@@ -85,16 +78,11 @@ static void writePSG(uint8_t address, uint8_t data) {
 
   // set inactive again
   BUS_OP_NACT();
-
-  // deselect chip
-  //BUS_OP_DISABLE_CS();
 }
 
 static void writeFrequency(uint8_t channel, uint16_t frequencyCode) {
-  uint8_t fine = frequencyCode & 0x00ff;
-  uint8_t coarse = (frequencyCode >> 8) & 0x000f;
-  writePSG(R0 + (channel * 2), fine);
-  writePSG(R1 + (channel * 2), coarse);
+  writePSG(R0 + (channel * 2), (frequencyCode & 0x00ff));
+  writePSG(R1 + (channel * 2), ((frequencyCode >> 8) & 0x000f));
 }
 
 int main() {
@@ -137,14 +125,12 @@ int main() {
   delay();
   
   // bus control lines
-  // BIT0: BC1
+  // BIT3: BC1
   // BIT1: BDIR
-  // BIT3: /CS
-  P1DIR |= BIT0 | BIT1 | BIT3;
+  P1DIR |= BIT1 | BIT3;
 
   // put bus into inactive state
   BUS_CTRL_REG &= ~(BDIR | BC1);
-  BUS_CTRL_REG |= _CS;
   
   // release sound chip from reset state
   P1OUT |= BIT2;
@@ -153,11 +139,12 @@ int main() {
   delay();
   
 
+  schInit();
+
   __enable_interrupt();
 
 
 
-  BUS_OP_ENABLE_CS();
 
   /*
   // single tone
@@ -191,9 +178,9 @@ int main() {
 
   /*
   // Akkord
-  writeFrequency(0, 01527);
-  writeFrequency(1, 01247);
-  writeFrequency(2, 01073);
+  writeFrequency(0, C5);
+  writeFrequency(1, E5);
+  writeFrequency(2, G5);
   writePSG(R7, 0b11111000);
   writePSG(R10, 03);
   writePSG(R11, 03);
@@ -201,9 +188,9 @@ int main() {
   */
 
 
-  BUS_OP_DISABLE_CS();
 
 
   while (1) {
+    schExec();
   }
 }
diff --git a/sound-driver/scheduler.c b/sound-driver/scheduler.c
new file mode 100644
index 0000000..90720aa
--- /dev/null
+++ b/sound-driver/scheduler.c
@@ -0,0 +1,86 @@
+#include <stdlib.h>
+#include <msp430g2553.h>
+#include "scheduler.h"
+
+tTask tasks[MAX_NUM_OF_TASKS];
+
+
+void schInit() {
+  P1DIR |= BIT0;
+  TACCR0 = 19600;
+  TACCTL0 = CCIE;
+  TACTL = MC_1 | ID_0 | TASSEL_2 | TACLR;
+
+  for (uint16_t i = 0; i < MAX_NUM_OF_TASKS; i++) {
+    tasks[i].delay = 0;
+    tasks[i].period = 0;
+    tasks[i].run = 0;
+    tasks[i].exec = NULL;
+    tasks[i].handle = NULL;
+  }
+}
+
+void __attribute__ ((interrupt (TIMER0_A0_VECTOR))) schUpdate() {
+  P1OUT ^= BIT0;
+  for (uint16_t i = 0; i < MAX_NUM_OF_TASKS; i++) {
+    if (tasks[i].exec != NULL) {
+      if (tasks[i].delay == 0) {
+        tasks[i].delay = tasks[i].period;
+        tasks[i].run++;
+      } else {
+        tasks[i].delay--;
+      }
+    }
+  }
+}
+
+void schAdd(void (*exec)(void *), void *handle, uint32_t delay, uint32_t period) {
+  for (uint16_t i = 0; i < MAX_NUM_OF_TASKS; i++) {
+    if (tasks[i].exec == NULL) {
+      tasks[i].delay = delay;
+      tasks[i].period = period;
+      if (delay == 0 && period == 0) {
+        tasks[i].run = 1;
+      } else {
+        tasks[i].run = 0;
+      }
+      tasks[i].exec = exec;
+      tasks[i].handle = handle;
+      break;
+    }
+  }
+}
+
+/*
+void schDel(void (*exec)(void *), void *handle) {
+  for (uint16_t i = 0; i < MAX_NUM_OF_TASKS; i++) {
+    if ((tasks[i].exec == exec) && (tasks[i].handle == handle)) {
+      tasks[i].exec = NULL;
+      break;
+    }
+  }
+}
+*/
+
+void schExec() {
+  for (uint16_t i = 0; i < MAX_NUM_OF_TASKS; i++) {
+    // synchronize access to tasks[].run
+    __disable_interrupt(); 
+    if (tasks[i].exec != NULL && tasks[i].run > 0) {
+      tasks[i].run--;
+      // synchronize access to tasks[].run
+      // reenable interrupts before actually executing task
+      __enable_interrupt();
+      tasks[i].exec(tasks[i].handle);
+      if (tasks[i].period == 0) {
+        tasks[i].exec = NULL;
+      }
+    } else {
+      // synchronize access to tasks[].run
+      // reenable interrupts in case task is not yet executable
+      __enable_interrupt();
+    }
+  }
+}
+
+
diff --git a/sound-driver/scheduler.h b/sound-driver/scheduler.h
new file mode 100644
index 0000000..510818e
--- /dev/null
+++ b/sound-driver/scheduler.h
@@ -0,0 +1,29 @@
+#ifndef PONTCOOPSCHEDULER_H_
+#define PONTCOOPSCHEDULER_H_
+
+
+#include <stdint.h>
+
+
+
+#define MAX_NUM_OF_TASKS 2
+
+
+typedef struct {
+  uint16_t delay;
+  uint16_t period;
+  uint8_t run;
+  void (*exec)(void *handle);
+  void *handle;
+} tTask;
+
+
+void schInit();
+void schAdd(void (*exec)(void *), void *handle, uint32_t delay, uint32_t period);
+void schDel(void (*exec)(void *), void *handle);
+void schExec();
+void schUpdate();
+uint8_t schTaskCnt();
+
+
+#endif /* PONTCOOPSCHEDULER_H_ */