diff --git a/CHANGES b/CHANGES
index f74d7ce0c..c67f7d85b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -62,6 +62,7 @@ Misc:
  - Perf: Ability to load savestates immediately on launch
  - Qt: Replace pause-after-frame mutex with an atomic
  - Util: Allow disabling the threading code entirely
+ - GBA: SIO logging layer
 
 0.2.1: (2015-05-13)
 Bugfixes:
diff --git a/src/gba/gba.h b/src/gba/gba.h
index 92fedfa91..0926470c5 100644
--- a/src/gba/gba.h
+++ b/src/gba/gba.h
@@ -46,8 +46,9 @@ enum GBALogLevel {
 	GBA_LOG_GAME_ERROR = 0x100,
 	GBA_LOG_SWI = 0x200,
 	GBA_LOG_STATUS = 0x400,
+	GBA_LOG_SIO = 0x800,
 
-	GBA_LOG_ALL = 0x73F,
+	GBA_LOG_ALL = 0xF3F,
 
 #ifdef NDEBUG
 	GBA_LOG_DANGER = GBA_LOG_ERROR
diff --git a/src/gba/sio/lockstep.c b/src/gba/sio/lockstep.c
index 842db4571..d8efe3390 100644
--- a/src/gba/sio/lockstep.c
+++ b/src/gba/sio/lockstep.c
@@ -82,6 +82,7 @@ bool GBASIOLockstepNodeInit(struct GBASIODriver* driver) {
 	struct GBASIOLockstepNode* node = (struct GBASIOLockstepNode*) driver;
 	node->nextEvent = LOCKSTEP_INCREMENT;
 	node->d.p->multiplayerControl.slave = node->id > 0;
+	GBALog(node->d.p->p, GBA_LOG_SIO, "Lockstep %i: Node init", node->id);
 	return true;
 }
 
@@ -115,9 +116,11 @@ bool GBASIOLockstepNodeUnload(struct GBASIODriver* driver) {
 static uint16_t GBASIOLockstepNodeWriteRegister(struct GBASIODriver* driver, uint32_t address, uint16_t value) {
 	struct GBASIOLockstepNode* node = (struct GBASIOLockstepNode*) driver;
 	if (address == REG_SIOCNT) {
+		GBALog(node->d.p->p, GBA_LOG_SIO, "Lockstep %i: SIOCNT <- %04x", node->id, value);
 		if (value & 0x0080) {
 			value &= ~0x0080;
 			if (!node->id) {
+				GBALog(node->d.p->p, GBA_LOG_SIO, "Lockstep %i: Transfer initiated", node->id);
 				MutexLock(&node->p->mutex);
 				node->p->transferActive = true;
 				node->p->transferCycles = GBASIOCyclesPerTransfer[node->d.p->multiplayerControl.baud][node->p->attached - 1];
@@ -126,6 +129,8 @@ static uint16_t GBASIOLockstepNodeWriteRegister(struct GBASIODriver* driver, uin
 		}
 		value &= 0xFF03;
 		value |= driver->p->siocnt & 0x007C;
+	} else if (address == REG_SIOMLT_SEND) {
+		GBALog(node->d.p->p, GBA_LOG_SIO, "Lockstep %i: SIOMLT_SEND <- %04x", node->id, value);
 	}
 	return value;
 }
@@ -162,6 +167,7 @@ static int32_t GBASIOLockstepNodeProcessEvents(struct GBASIODriver* driver, int3
 			ConditionWake(&node->p->barrier);
 		}
 		if (node->state == LOCKSTEP_FINISHED) {
+			GBALog(node->d.p->p, GBA_LOG_SIO, "Lockstep %i: Finishing transfer: %04x %04x %04x %04x", node->id, node->p->multiRecv[0], node->p->multiRecv[1], node->p->multiRecv[2], node->p->multiRecv[3]);
 			node->d.p->p->memory.io[REG_SIOMULTI0 >> 1] = node->p->multiRecv[0];
 			node->d.p->p->memory.io[REG_SIOMULTI1 >> 1] = node->p->multiRecv[1];
 			node->d.p->p->memory.io[REG_SIOMULTI2 >> 1] = node->p->multiRecv[2];
diff --git a/src/platform/qt/LogView.cpp b/src/platform/qt/LogView.cpp
index 15a299480..bd9832def 100644
--- a/src/platform/qt/LogView.cpp
+++ b/src/platform/qt/LogView.cpp
@@ -26,6 +26,7 @@ LogView::LogView(QWidget* parent)
 	connect(m_ui.levelGameError, SIGNAL(toggled(bool)), this, SLOT(setLevelGameError(bool)));
 	connect(m_ui.levelSWI, SIGNAL(toggled(bool)), this, SLOT(setLevelSWI(bool)));
 	connect(m_ui.levelStatus, SIGNAL(toggled(bool)), this, SLOT(setLevelStatus(bool)));
+	connect(m_ui.levelSIO, SIGNAL(toggled(bool)), this, SLOT(setLevelSIO(bool)));
 	connect(m_ui.clear, SIGNAL(clicked()), this, SLOT(clear()));
 	connect(m_ui.maxLines, SIGNAL(valueChanged(int)), this, SLOT(setMaxLines(int)));
 	m_ui.maxLines->setValue(DEFAULT_LINE_LIMIT);
@@ -59,6 +60,7 @@ void LogView::setLevels(int levels) {
 	m_ui.levelGameError->setCheckState(levels & GBA_LOG_GAME_ERROR ? Qt::Checked : Qt::Unchecked);
 	m_ui.levelSWI->setCheckState(levels & GBA_LOG_SWI ? Qt::Checked : Qt::Unchecked);
 	m_ui.levelStatus->setCheckState(levels & GBA_LOG_STATUS ? Qt::Checked : Qt::Unchecked);
+	m_ui.levelSIO->setCheckState(levels & GBA_LOG_SIO ? Qt::Checked : Qt::Unchecked);
 
 	emit levelsSet(levels);
 }
@@ -135,6 +137,14 @@ void LogView::setLevelStatus(bool set) {
 	}
 }
 
+void LogView::setLevelSIO(bool set) {
+	if (set) {
+		setLevel(GBA_LOG_SIO);
+	} else {
+		clearLevel(GBA_LOG_SIO);
+	}
+}
+
 void LogView::setMaxLines(int limit) {
 	m_lineLimit = limit;
 	while (m_lines > m_lineLimit) {
@@ -162,6 +172,8 @@ QString LogView::toString(int level) {
 		return tr("SWI");
 	case GBA_LOG_STATUS:
 		return tr("STATUS");
+	case GBA_LOG_SIO:
+		return tr("SIO");
 	}
 	return QString();
 }
diff --git a/src/platform/qt/LogView.h b/src/platform/qt/LogView.h
index 66eb18b71..28658672e 100644
--- a/src/platform/qt/LogView.h
+++ b/src/platform/qt/LogView.h
@@ -41,6 +41,7 @@ public slots:
 	void setLevelGameError(bool);
 	void setLevelSWI(bool);
 	void setLevelStatus(bool);
+	void setLevelSIO(bool);
 
 	void setMaxLines(int);
 
diff --git a/src/platform/qt/LogView.ui b/src/platform/qt/LogView.ui
index 020c826ad..64e2642ec 100644
--- a/src/platform/qt/LogView.ui
+++ b/src/platform/qt/LogView.ui
@@ -116,6 +116,13 @@
           </property>
          </widget>
         </item>
+        <item>
+         <widget class="QCheckBox" name="levelSIO">
+          <property name="text">
+           <string>Serial I/O</string>
+          </property>
+         </widget>
+        </item>
        </layout>
       </widget>
      </item>