diff --git a/src/bus.c b/src/bus.c
index c3bf3ef..95e8f0b 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -2,15 +2,18 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include <string.h>
 #include <unistd.h>
 #include <assert.h>
 #include <fcntl.h>
+#include <errno.h>
 
 #include <sys/types.h>
 
 #include <utlist.h>
 
 #include "bus.h"
+#include "log.h"
 
 #include "device_ram.h"
 
@@ -68,7 +71,7 @@ bus_access_device(bus_t *t, uint16_t addr, device_t **d, uint16_t *off)
 	}
 
 	if (*d == NULL) {
-		fprintf(stderr, "Hitting unmapped bus space @ %x!", addr);
+		rk6502_log(LOG_WARN, "Hitting unmapped bus space @ %x!", addr);
 		return;
 	}
 
@@ -90,7 +93,8 @@ bus_read_1(bus_t *t, uint16_t addr)
 		val = d->read_1(d, off);
 
 	if (t->access_debug)
-		printf("bus READ @ %x (off %x) value %x\n", addr, off, val); 
+		rk6502_log(LOG_DEBUG, "bus READ @ %x (off %x) value %x\n",
+		    addr, off, val); 
 
 	return val;
 }
@@ -104,7 +108,8 @@ bus_write_1(bus_t *t, uint16_t addr, uint8_t val)
 	bus_access_device(t, addr, &d, &off);
 
 	if (t->access_debug)
-		printf("bus WRITE @ %x (off %x) value %x\n", addr, off, val); 
+		rk6502_log(LOG_DEBUG, "bus WRITE @ %x (off %x) value %x\n",
+		    addr, off, val); 
 
 	d->write_1(d, off, val);
 }
@@ -158,7 +163,8 @@ bus_load_file(bus_t *t, uint16_t addr, const char *filename)
 
 	fd = open(filename, O_RDONLY);
 	if (fd == -1) {
-		perror("Problem while trying to open file");
+		rk6502_log(LOG_ERROR, "Problem while trying to open file: %s",
+		    strerror(errno));
 		return false;
 	}
 
diff --git a/src/debug.c b/src/debug.c
index 90cdfdc..950c519 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -4,6 +4,7 @@
 
 #include "rk65c02.h"
 #include "instruction.h"
+#include "log.h"
 #include "debug.h"
 
 void
@@ -26,7 +27,7 @@ debug_trace_print_all(rk65c02emu_t *e)
 		i.op1 = tr->op1;
 		i.op2 = tr->op2;
 
-		printf("TRACE %X:\t", tr->address);
+		rk6502_log(LOG_TRACE, " %X:\t", tr->address);
 		instruction_print(&i);
 		printf("\t");
 		rk65c02_dump_regs(tr->regs);
diff --git a/src/instruction.c b/src/instruction.c
index 19af558..0f6927b 100644
--- a/src/instruction.c
+++ b/src/instruction.c
@@ -9,6 +9,7 @@
 #include "bus.h"
 #include "rk65c02.h"
 #include "65c02isa.h"
+#include "log.h"
 #include "instruction.h"
 
 instruction_t
@@ -172,14 +173,16 @@ assemble_single_buf(uint8_t **buf, uint8_t *bsize, const char *mnemonic, address
 	}
 
 	if (!found) {
-		fprintf(stderr, "Couldn't find opcode for mnemonic %s mode %x\n", mnemonic, mode);
+		rk6502_log(LOG_ERROR,
+		    "Couldn't find opcode for mnemonic %s mode %x.",
+		    mnemonic, mode);
 		return false;
 	}
 
 	*bsize = id.size;
 	*buf = malloc(id.size);
 	if(*buf == NULL) {
-		fprintf(stderr, "Error allocating assembly buffer\n");
+		rk6502_log(LOG_ERROR, "Error allocating assembly buffer.");
 		return false;
 	}
 
@@ -301,8 +304,8 @@ instruction_data_write_1(rk65c02emu_t *e, instrdef_t *id, instruction_t *i, uint
 		 * PC which is handled within emulation of a given opcode.
 		 */
 	default:
-		printf("unhandled addressing mode for opcode %x\n",
-		    i->opcode);
+		rk6502_log(LOG_ERROR,
+		    "unhandled addressing mode for opcode %x\n", i->opcode);
 		break;
 	}
 }
@@ -368,8 +371,8 @@ instruction_data_read_1(rk65c02emu_t *e, instrdef_t *id, instruction_t *i)
 		 * PC which is handled within emulation of a given opcode.
 		 */
 	default:
-		printf("unhandled addressing mode for opcode %x\n",
-		    i->opcode);
+		rk6502_log(LOG_ERROR,
+		    "unhandled addressing mode for opcode %x\n", i->opcode);
 		break;
 	}
 
diff --git a/src/log.c b/src/log.c
index 15dde25..650b738 100644
--- a/src/log.c
+++ b/src/log.c
@@ -1,6 +1,8 @@
 #include <stdio.h>
 #include <stdarg.h>
 
+#include <sys/time.h>
+
 #include "log.h"
 
 static const char *level_str[] = {
@@ -22,11 +24,15 @@ void rk6502_loglevel_set(uint8_t l)
 void rk6502_log(uint8_t l, const char* fmt, ...)
 {
 	va_list args;
+	struct timeval t;
+	
+	gettimeofday(&t, NULL);
 
 	if (l > level)
 		return;
 
-	fprintf(stderr, "%s:\t", level_str[l]);
+	fprintf(stderr, "%ld %s:\t", (t.tv_sec * 1000000 + t.tv_usec),
+	    level_str[l]);
 
 	va_start(args, fmt);
 	vfprintf(stderr, fmt, args);
diff --git a/src/log.h b/src/log.h
index 99c0eac..738ff8b 100644
--- a/src/log.h
+++ b/src/log.h
@@ -3,6 +3,7 @@
 #define LOG_TRACE	5
 #define LOG_DEBUG	4
 #define LOG_INFO	3
+#define LOG_WARN	4
 #define LOG_ERROR	2
 #define LOG_CRIT	1
 #define LOG_NOTHING	0	/* At 0 nothing will get logged, can be set as
diff --git a/src/rk65c02.c b/src/rk65c02.c
index 8b95f06..04b6af6 100644
--- a/src/rk65c02.c
+++ b/src/rk65c02.c
@@ -119,8 +119,8 @@ rk65c02_exec(rk65c02emu_t *e)
 		if (!instruction_modify_pc(&id)) 
 			program_counter_increment(e, &id);
 	} else {
-		printf("unimplemented opcode %X @ %X\n", i.opcode,
-		    e->regs.PC);
+		rk6502_log(LOG_ERROR, "unimplemented opcode %X @ %X\n",
+		    i.opcode, e->regs.PC);
 		e->state = STOPPED;
 		e->stopreason = EMUERROR;
 	}
diff --git a/test/test_debug.c b/test/test_debug.c
index f3231e2..fde4017 100644
--- a/test/test_debug.c
+++ b/test/test_debug.c
@@ -12,6 +12,7 @@
 #include "instruction.h"
 #include "debug.h"
 #include "utils.h"
+#include "log.h"
 
 ATF_TC_WITHOUT_HEAD(breakpoint);
 ATF_TC_BODY(breakpoint, tc)
@@ -54,10 +55,13 @@ ATF_TC_BODY(trace, tc)
 	trace_t *tr;
 	int i;
 
+	rk6502_loglevel_set(LOG_TRACE);
+
 	b = bus_init_with_default_devs();
 	a = assemble_init(&b, ROM_LOAD_ADDR);
 	e = rk65c02_init(&b);
 
+
 	e.regs.PC = ROM_LOAD_ADDR;
 	debug_trace_set(&e, true);