diff --git a/Downstream/Inc/downstream_hid.h b/Downstream/Inc/downstream_hid.h
index 640f9b6..2a7bc6e 100644
--- a/Downstream/Inc/downstream_hid.h
+++ b/Downstream/Inc/downstream_hid.h
@@ -42,10 +42,12 @@
 #define HID_ITEM_INPUT_REL          0x06
 
 
+typedef void (*TransactionCompleteCallbackTypeDef)(void);
 
 InterfaceCommandClassTypeDef Downstream_HID_ApproveConnectedDevice(void);
 void Downstream_HID_PacketProcessor(DownstreamPacketTypeDef* receivedPacket);
-void Downstream_HID_InterruptReportCallback(DownstreamPacketTypeDef* packetToSend);
+void Downstream_HID_InterruptReportCallback(void);
+void Downstream_HID_SendReportCallback(void);
 
 
 
diff --git a/Downstream/Inc/downstream_interface_def.h b/Downstream/Inc/downstream_interface_def.h
index bf815ab..dd6b538 100644
--- a/Downstream/Inc/downstream_interface_def.h
+++ b/Downstream/Inc/downstream_interface_def.h
@@ -58,7 +58,7 @@ InterfaceCommandMscTypeDef;
 typedef enum
 {
     COMMAND_HID_GET_REPORT,         //Returns HID report from device
-    COMMAND_HID_SET_REPORT          //Sends HID report to device. No reply or ack expected.
+    COMMAND_HID_SET_REPORT          //Sends HID report to device. Simple ack packet contains no data.
 }
 InterfaceCommandHidTypeDef;
 
diff --git a/Downstream/Inc/downstream_spi.h b/Downstream/Inc/downstream_spi.h
index f8941a1..6f59a6f 100644
--- a/Downstream/Inc/downstream_spi.h
+++ b/Downstream/Inc/downstream_spi.h
@@ -71,6 +71,7 @@ typedef void (*SpiPacketReceivedCallbackTypeDef)(DownstreamPacketTypeDef* receiv
 
 void Downstream_InitSPI(void);
 HAL_StatusTypeDef Downstream_GetFreePacket(FreePacketCallbackTypeDef callback);
+DownstreamPacketTypeDef* Downstream_GetFreePacketImmediately(void);
 void Downstream_ReleasePacket(DownstreamPacketTypeDef* packetToRelease);
 HAL_StatusTypeDef Downstream_ReceivePacket(SpiPacketReceivedCallbackTypeDef callback);
 HAL_StatusTypeDef Downstream_TransmitPacket(DownstreamPacketTypeDef* packetToWrite);
diff --git a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Inc/usbh_hid.h b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Inc/usbh_hid.h
index 96e123f..e8acdd4 100644
--- a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Inc/usbh_hid.h
+++ b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Inc/usbh_hid.h
@@ -23,6 +23,9 @@
   * limitations under the License.
   *
   ******************************************************************************
+  *
+  * Modifications by Robert Fisk
+  *
   */ 
 
 /* Define to prevent recursive  ----------------------------------------------*/
@@ -35,7 +38,7 @@
 
 /* Includes ------------------------------------------------------------------*/
 #include "usbh_core.h"
-#include "downstream_spi.h"
+#include "downstream_hid.h"
 
  
 /** @addtogroup USBH_LIB
@@ -105,6 +108,10 @@
 #define  HID_LOCAL_ITEM_TAG_STRING_MIN              0x08
 #define  HID_LOCAL_ITEM_TAG_STRING_MAX              0x09
 #define  HID_LOCAL_ITEM_TAG_DELIMITER               0x0A
+
+
+#define HID_REPORT_DIRECTION_IN                     0x01
+#define HID_REPORT_DIRECTION_OUT                    0x02
     
 
 /* States for HID State Machine */
@@ -114,8 +121,7 @@ typedef enum
   HID_IDLE,
   HID_GET_DATA,
   HID_GET_POLL,
-  HID_SET_DATA,
-  HID_SET_POLL,
+  HID_SET_DATA_POLL,
   HID_ERROR,
 }
 HID_StateTypeDef;
@@ -227,7 +233,7 @@ typedef struct _HID_Process
   uint8_t              ep_addr;
   uint8_t              Protocol;
   HID_DescTypeDef      HID_Desc;
-  FreePacketCallbackTypeDef   ReportCallback;
+  TransactionCompleteCallbackTypeDef   ReportCallback;
   uint8_t              Data[HID_MAX_REPORT_SIZE];
 }
 HID_HandleTypeDef;
@@ -288,7 +294,8 @@ USBH_StatusTypeDef USBH_HID_SetReport (USBH_HandleTypeDef *phost,
                                   uint8_t reportType,
                                   uint8_t reportId,
                                   uint8_t* reportBuff,
-                                  uint8_t reportLen);
+                                  uint8_t reportLen,
+                                  TransactionCompleteCallbackTypeDef callback);
   
 USBH_StatusTypeDef USBH_HID_GetReport (USBH_HandleTypeDef *phost,
                                   uint8_t reportType,
@@ -322,7 +329,7 @@ uint16_t  fifo_read(FIFO_TypeDef * f, void * buf, uint16_t  nbytes);
 uint16_t  fifo_write(FIFO_TypeDef * f, const void * buf, uint16_t  nbytes);
 
 HAL_StatusTypeDef USBH_HID_GetInterruptReport(USBH_HandleTypeDef *phost,
-                                              FreePacketCallbackTypeDef callback);
+                                              TransactionCompleteCallbackTypeDef callback);
 
 
 /**
diff --git a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Src/usbh_hid.c b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Src/usbh_hid.c
index c0416b9..49d9188 100644
--- a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Src/usbh_hid.c
+++ b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/HID/Src/usbh_hid.c
@@ -373,17 +373,17 @@ static USBH_StatusTypeDef USBH_HID_Process(USBH_HandleTypeDef *phost)
                                   HID_Handle->Data,
                                   HID_Handle->length,
                                   HID_Handle->InPipe);
-
         HID_Handle->state = HID_GET_POLL;
         HID_Handle->timer = phost->Timer;
       }
     break;
+
   case HID_GET_POLL:
     urbStatus = USBH_LL_GetURBState(phost, HID_Handle->InPipe);
     
     if (urbStatus == USBH_URB_DONE)
     {
-        Downstream_GetFreePacket(HID_Handle->ReportCallback);
+        HID_Handle->ReportCallback();
         HID_Handle->state = HID_IDLE;
         break;
     }
@@ -405,15 +405,14 @@ static USBH_StatusTypeDef USBH_HID_Process(USBH_HandleTypeDef *phost)
     }
     break;
 
-  case HID_SET_DATA:
-
-      break;
-
-  case HID_SET_POLL:
-
+  case HID_SET_DATA_POLL:
+      if (USBH_CtlReq(phost, HID_Handle->Data, phost->Control.setup.b.wLength.w) == USBH_OK)
+      {
+          HID_Handle->ReportCallback();
+          HID_Handle->state = HID_IDLE;
+      }
       break;
 
-
   case HID_IDLE:
       break;
 
@@ -441,7 +440,7 @@ static USBH_StatusTypeDef USBH_HID_SOFProcess(USBH_HandleTypeDef *phost)
 //Downstream_HID calls into here at main() priority,
 //to request a new report for Upstream.
 HAL_StatusTypeDef USBH_HID_GetInterruptReport(USBH_HandleTypeDef *phost,
-                                              FreePacketCallbackTypeDef callback)
+                                              TransactionCompleteCallbackTypeDef callback)
 {
     HID_HandleTypeDef *HID_Handle =  (HID_HandleTypeDef *) phost->pActiveClass->pData;
 
@@ -452,7 +451,8 @@ HAL_StatusTypeDef USBH_HID_GetInterruptReport(USBH_HandleTypeDef *phost,
         return HAL_OK;
     }
 
-    return HAL_ERROR;
+    //return HAL_ERROR;
+    while (1);
 }
 
 
@@ -533,16 +533,18 @@ USBH_StatusTypeDef USBH_HID_SetIdle (USBH_HandleTypeDef *phost,
                                          uint8_t duration,
                                          uint8_t reportId)
 {
-  
-  phost->Control.setup.b.bmRequestType = USB_H2D | USB_REQ_RECIPIENT_INTERFACE |\
-    USB_REQ_TYPE_CLASS;
-  
-  
-  phost->Control.setup.b.bRequest = USB_HID_SET_IDLE;
-  phost->Control.setup.b.wValue.w = (duration << 8 ) | reportId;
-  
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = 0;
+    if (phost->RequestState == CMD_SEND)
+    {
+        phost->Control.setup.b.bmRequestType = USB_H2D |
+                                               USB_REQ_RECIPIENT_INTERFACE |
+                                               USB_REQ_TYPE_CLASS;
+
+        phost->Control.setup.b.bRequest = USB_HID_SET_IDLE;
+        phost->Control.setup.b.wValue.w = (duration << 8 ) | reportId;
+
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = 0;
+    }
   
   return USBH_CtlReq(phost, 0 , 0 );
 }
@@ -562,20 +564,41 @@ USBH_StatusTypeDef USBH_HID_SetReport (USBH_HandleTypeDef *phost,
                                     uint8_t reportType,
                                     uint8_t reportId,
                                     uint8_t* reportBuff,
-                                    uint8_t reportLen)
+                                    uint8_t reportLen,
+                                    TransactionCompleteCallbackTypeDef callback)
 {
+    HID_HandleTypeDef *HID_Handle =  (HID_HandleTypeDef *) phost->pActiveClass->pData;
+    uint32_t i;
+
+    if (phost->RequestState == CMD_SEND)
+    {
+        if ((HID_Handle->state != HID_IDLE) ||
+            (reportLen > HID_MAX_REPORT_SIZE))
+        {
+            while (1);
+        }
+
+        HID_Handle->ReportCallback = callback;
+        HID_Handle->state = HID_SET_DATA_POLL;
+        for (i = 0; i < reportLen; i++)
+        {
+            HID_Handle->Data[i] = *reportBuff;
+            reportBuff++;
+        }
+
+        phost->Control.setup.b.bmRequestType = USB_H2D |
+                                               USB_REQ_RECIPIENT_INTERFACE |
+                                               USB_REQ_TYPE_CLASS;
+
+        phost->Control.setup.b.bRequest = USB_HID_SET_REPORT;
+        phost->Control.setup.b.wValue.w = (reportType << 8 ) | reportId;
+
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = reportLen;
+    }
   
-  phost->Control.setup.b.bmRequestType = USB_H2D | USB_REQ_RECIPIENT_INTERFACE |\
-    USB_REQ_TYPE_CLASS;
-  
-  
-  phost->Control.setup.b.bRequest = USB_HID_SET_REPORT;
-  phost->Control.setup.b.wValue.w = (reportType << 8 ) | reportId;
-  
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = reportLen;
-  
-  return USBH_CtlReq(phost, reportBuff , reportLen );
+    //return USBH_CtlReq(phost, reportBuff, reportLen);
+    return USBH_OK;
 }
 
 
@@ -595,17 +618,19 @@ USBH_StatusTypeDef USBH_HID_GetReport (USBH_HandleTypeDef *phost,
                                     uint8_t* reportBuff,
                                     uint8_t reportLen)
 {
-  
-  phost->Control.setup.b.bmRequestType = USB_D2H | USB_REQ_RECIPIENT_INTERFACE |\
-    USB_REQ_TYPE_CLASS;
-  
-  
-  phost->Control.setup.b.bRequest = USB_HID_GET_REPORT;
-  phost->Control.setup.b.wValue.w = (reportType << 8 ) | reportId;
-  
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = reportLen;
-  
+    if (phost->RequestState == CMD_SEND)
+    {
+        phost->Control.setup.b.bmRequestType = USB_D2H |
+                                               USB_REQ_RECIPIENT_INTERFACE |
+                                               USB_REQ_TYPE_CLASS;
+
+        phost->Control.setup.b.bRequest = USB_HID_GET_REPORT;
+        phost->Control.setup.b.wValue.w = (reportType << 8 ) | reportId;
+
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = reportLen;
+    }
+
   return USBH_CtlReq(phost, reportBuff , reportLen );
 }
 
@@ -619,16 +644,17 @@ USBH_StatusTypeDef USBH_HID_GetReport (USBH_HandleTypeDef *phost,
 USBH_StatusTypeDef USBH_HID_SetProtocol(USBH_HandleTypeDef *phost,
                                             uint8_t protocol)
 {
-  
-  
-  phost->Control.setup.b.bmRequestType = USB_H2D | USB_REQ_RECIPIENT_INTERFACE |\
-    USB_REQ_TYPE_CLASS;
-  
-  
-  phost->Control.setup.b.bRequest = USB_HID_SET_PROTOCOL;
-  phost->Control.setup.b.wValue.w = protocol == 0 ? 0 : 1;
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = 0;
+    if (phost->RequestState == CMD_SEND)
+    {
+        phost->Control.setup.b.bmRequestType = USB_H2D |
+                                               USB_REQ_RECIPIENT_INTERFACE |\
+                                               USB_REQ_TYPE_CLASS;
+
+        phost->Control.setup.b.bRequest = USB_HID_SET_PROTOCOL;
+        phost->Control.setup.b.wValue.w = protocol == 0 ? 0 : 1;
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = 0;
+    }
   
   return USBH_CtlReq(phost, 0 , 0 );
   
diff --git a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/MSC/Src/usbh_msc_bot.c b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/MSC/Src/usbh_msc_bot.c
index b96563f..32b68af 100644
--- a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/MSC/Src/usbh_msc_bot.c
+++ b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Class/MSC/Src/usbh_msc_bot.c
@@ -58,14 +58,17 @@ USBH_HandleTypeDef *Callback_MSC_phost;
   */
 USBH_StatusTypeDef USBH_MSC_BOT_REQ_Reset(USBH_HandleTypeDef *phost)
 {
-  
-  phost->Control.setup.b.bmRequestType = USB_H2D | USB_REQ_TYPE_CLASS | \
-                              USB_REQ_RECIPIENT_INTERFACE;
-  
-  phost->Control.setup.b.bRequest = USB_REQ_BOT_RESET;
-  phost->Control.setup.b.wValue.w = 0;
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = 0;           
+    if (phost->RequestState == CMD_SEND)
+    {
+        phost->Control.setup.b.bmRequestType = USB_H2D |
+                                               USB_REQ_TYPE_CLASS |
+                                               USB_REQ_RECIPIENT_INTERFACE;
+
+        phost->Control.setup.b.bRequest = USB_REQ_BOT_RESET;
+        phost->Control.setup.b.wValue.w = 0;
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = 0;
+    }
   
   return USBH_CtlReq(phost, 0 , 0 );  
 }
@@ -79,13 +82,17 @@ USBH_StatusTypeDef USBH_MSC_BOT_REQ_Reset(USBH_HandleTypeDef *phost)
   */
 USBH_StatusTypeDef USBH_MSC_BOT_REQ_GetMaxLUN(USBH_HandleTypeDef *phost, uint8_t *Maxlun)
 {
-  phost->Control.setup.b.bmRequestType = USB_D2H | USB_REQ_TYPE_CLASS | \
-                              USB_REQ_RECIPIENT_INTERFACE;
-  
-  phost->Control.setup.b.bRequest = USB_REQ_GET_MAX_LUN;
-  phost->Control.setup.b.wValue.w = 0;
-  phost->Control.setup.b.wIndex.w = 0;
-  phost->Control.setup.b.wLength.w = 1;           
+    if (phost->RequestState == CMD_SEND)
+    {
+        phost->Control.setup.b.bmRequestType = USB_D2H |
+                                               USB_REQ_TYPE_CLASS |
+                                               USB_REQ_RECIPIENT_INTERFACE;
+
+        phost->Control.setup.b.bRequest = USB_REQ_GET_MAX_LUN;
+        phost->Control.setup.b.wValue.w = 0;
+        phost->Control.setup.b.wIndex.w = 0;
+        phost->Control.setup.b.wLength.w = 1;
+    }
   
   return USBH_CtlReq(phost, Maxlun , 1 ); 
 }
diff --git a/Downstream/Src/downstream_hid.c b/Downstream/Src/downstream_hid.c
index 7d25095..0484ed2 100644
--- a/Downstream/Src/downstream_hid.c
+++ b/Downstream/Src/downstream_hid.c
@@ -56,6 +56,7 @@ uint8_t ItemData;
 static HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void);
 static HAL_StatusTypeDef Downstream_HID_GetNextReportItem(void);
 static void Downstream_HID_Mouse_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend);
+static void Downstream_HID_Keyboard_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend);
 static uint8_t Downstream_HID_Mouse_Extract8BitValue(HID_HandleTypeDef* hidHandle,
                                                      uint8_t valueBitOffset,
                                                      uint8_t valueBitLength);
@@ -84,7 +85,7 @@ InterfaceCommandClassTypeDef Downstream_HID_ApproveConnectedDevice(void)
 
 
 
-HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void)
+static HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void)
 {
     uint32_t currentReportBitIndex = 0;
     uint8_t currentUsagePage = 0;
@@ -242,7 +243,7 @@ HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void)
 
 //Retrieves the next item in the HID report, and at most one of its associated data bytes.
 //Then it updates ReportDataPointer based on the actual length of the retrieved item.
-HAL_StatusTypeDef Downstream_HID_GetNextReportItem(void)
+static HAL_StatusTypeDef Downstream_HID_GetNextReportItem(void)
 {
     HID_HandleTypeDef* HID_Handle =  (HID_HandleTypeDef*)hUsbHostFS.pActiveClass->pData;
     uint32_t itemLength;
@@ -287,9 +288,22 @@ void Downstream_HID_PacketProcessor(DownstreamPacketTypeDef* receivedPacket)
         Downstream_PacketProcessor_NotifyDisconnectReplyRequired();
     }
 
-    if (receivedPacket->Command == COMMAND_HID_SET_REPORT)
+    else if (receivedPacket->Command == COMMAND_HID_SET_REPORT)
     {
-
+        if ((ConfiguredDeviceClass    != COMMAND_CLASS_HID_KEYBOARD) ||
+            (receivedPacket->Length16 != ((HID_KEYBOARD_OUTPUT_DATA_LEN + 1) / 2) + DOWNSTREAM_PACKET_HEADER_LEN_16) ||
+            ((receivedPacket->Data[0] & ~((1 << HID_KEYBOARD_MAX_LED) - 1)) != 0))
+        {
+            Downstream_PacketProcessor_FreakOut();
+        }
+        USBH_HID_SetReport(&hUsbHostFS,
+                           HID_REPORT_DIRECTION_OUT,
+                           0,
+                           receivedPacket->Data,
+                           HID_KEYBOARD_OUTPUT_DATA_LEN,
+                           Downstream_HID_SendReportCallback);
+        Downstream_ReleasePacket(receivedPacket);
+        Downstream_PacketProcessor_NotifyDisconnectReplyRequired();
     }
 
     //else:
@@ -297,17 +311,20 @@ void Downstream_HID_PacketProcessor(DownstreamPacketTypeDef* receivedPacket)
 }
 
 
-void Downstream_HID_InterruptReportCallback(DownstreamPacketTypeDef* packetToSend)
+void Downstream_HID_InterruptReportCallback(void)
 {
+    DownstreamPacketTypeDef* freePacket;
+
+    freePacket = Downstream_GetFreePacketImmediately();
     if (ConfiguredDeviceClass == COMMAND_CLASS_HID_MOUSE)
     {
-        Downstream_HID_Mouse_ExtractDataFromReport(packetToSend);
-        packetToSend->Length16 = ((HID_MOUSE_INPUT_DATA_LEN + 1) / 2) + DOWNSTREAM_PACKET_HEADER_LEN_16;
+        Downstream_HID_Mouse_ExtractDataFromReport(freePacket);
+        freePacket->Length16 = ((HID_MOUSE_INPUT_DATA_LEN + 1) / 2) + DOWNSTREAM_PACKET_HEADER_LEN_16;
     }
     else if (ConfiguredDeviceClass == COMMAND_CLASS_HID_KEYBOARD)
     {
-        Downstream_HID_Keyboard_ExtractDataFromReport(packetToSend);
-        packetToSend->Length16 = ((HID_KEYBOARD_INPUT_DATA_LEN + 1) / 2) + DOWNSTREAM_PACKET_HEADER_LEN_16;
+        Downstream_HID_Keyboard_ExtractDataFromReport(freePacket);
+        freePacket->Length16 = ((HID_KEYBOARD_INPUT_DATA_LEN + 1) / 2) + DOWNSTREAM_PACKET_HEADER_LEN_16;
     }
     //else if...
 
@@ -317,13 +334,13 @@ void Downstream_HID_InterruptReportCallback(DownstreamPacketTypeDef* packetToSen
         return;
     }
 
-    packetToSend->CommandClass = ConfiguredDeviceClass;
-    packetToSend->Command = COMMAND_HID_GET_REPORT;
-    Downstream_PacketProcessor_ClassReply(packetToSend);
+    freePacket->CommandClass = ConfiguredDeviceClass;
+    freePacket->Command = COMMAND_HID_GET_REPORT;
+    Downstream_PacketProcessor_ClassReply(freePacket);
 }
 
 
-void Downstream_HID_Mouse_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend)
+static void Downstream_HID_Mouse_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend)
 {
     HID_HandleTypeDef* HID_Handle =  (HID_HandleTypeDef*)hUsbHostFS.pActiveClass->pData;
     uint32_t readData;
@@ -348,9 +365,9 @@ void Downstream_HID_Mouse_ExtractDataFromReport(DownstreamPacketTypeDef* packetT
 
 
 
-uint8_t Downstream_HID_Mouse_Extract8BitValue(HID_HandleTypeDef* hidHandle,
-                                              uint8_t valueBitOffset,
-                                              uint8_t valueBitLength)
+static uint8_t Downstream_HID_Mouse_Extract8BitValue(HID_HandleTypeDef* hidHandle,
+                                                     uint8_t valueBitOffset,
+                                                     uint8_t valueBitLength)
 {
     int32_t readData;
 
@@ -371,7 +388,7 @@ uint8_t Downstream_HID_Mouse_Extract8BitValue(HID_HandleTypeDef* hidHandle,
 
 
 
-void Downstream_HID_Keyboard_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend)
+static void Downstream_HID_Keyboard_ExtractDataFromReport(DownstreamPacketTypeDef* packetToSend)
 {
     HID_HandleTypeDef* HID_Handle =  (HID_HandleTypeDef*)hUsbHostFS.pActiveClass->pData;
     uint32_t i;
@@ -392,3 +409,14 @@ void Downstream_HID_Keyboard_ExtractDataFromReport(DownstreamPacketTypeDef* pack
 }
 
 
+
+void Downstream_HID_SendReportCallback(void)
+{
+    DownstreamPacketTypeDef* freePacket;
+
+    freePacket = Downstream_GetFreePacketImmediately();
+    freePacket->CommandClass = ConfiguredDeviceClass;
+    freePacket->Command = COMMAND_HID_SET_REPORT;
+    Downstream_PacketProcessor_ClassReply(freePacket);
+}
+
diff --git a/Downstream/Src/downstream_spi.c b/Downstream/Src/downstream_spi.c
index 2c08354..575ecd7 100644
--- a/Downstream/Src/downstream_spi.c
+++ b/Downstream/Src/downstream_spi.c
@@ -92,6 +92,33 @@ HAL_StatusTypeDef Downstream_GetFreePacket(FreePacketCallbackTypeDef callback)
 }
 
 
+
+DownstreamPacketTypeDef* Downstream_GetFreePacketImmediately(void)
+{
+    if (DownstreamInterfaceState >= DOWNSTREAM_INTERFACE_ERROR)
+    {
+        return NULL;
+    }
+
+    //We are expecting a free buffer now
+    if (DownstreamPacket0.Busy == NOT_BUSY)
+    {
+        DownstreamPacket0.Busy = BUSY;
+        return &DownstreamPacket0;
+    }
+    if (DownstreamPacket1.Busy == NOT_BUSY)
+    {
+        DownstreamPacket1.Busy = BUSY;
+        return &DownstreamPacket1;
+    }
+
+    //Should not happen:
+    DOWNSTREAM_SPI_FREAKOUT;
+    return NULL;
+}
+
+
+
 //Used by Downstream state machine and USB host classes.
 void Downstream_ReleasePacket(DownstreamPacketTypeDef* packetToRelease)
 {
diff --git a/Downstream/Src/downstream_statemachine.c b/Downstream/Src/downstream_statemachine.c
index ae09dee..6ede375 100644
--- a/Downstream/Src/downstream_statemachine.c
+++ b/Downstream/Src/downstream_statemachine.c
@@ -10,7 +10,6 @@
  */
 
 
-#include <downstream_hid.h>
 #include "downstream_statemachine.h"
 #include "downstream_interface_def.h"
 #include "downstream_spi.h"
diff --git a/Upstream/Inc/upstream_hid.h b/Upstream/Inc/upstream_hid.h
index 78ef333..7d7f3f3 100644
--- a/Upstream/Inc/upstream_hid.h
+++ b/Upstream/Inc/upstream_hid.h
@@ -29,10 +29,16 @@
 #define HID_KEYBOARD_MAX_LED            3
 
 
-typedef uint8_t (*UpstreamHidGetReportCallback)(uint8_t *report,
-                                                 uint16_t len);
+typedef enum
+{
+    KEYBOARD_OUT_STATE_IDLE,
+    KEYBOARD_OUT_STATE_DATA_READY,
+    KEYBOARD_OUT_STATE_BUSY
+} KeyboardOutStateTypeDef;
 
 
+typedef uint8_t (*UpstreamHidGetReportCallback)(uint8_t *report,
+                                                uint16_t len);
 
 void Upstream_HID_DeInit(void);
 void Upstream_HID_GetNextInterruptReport(UpstreamHidGetReportCallback callback);
diff --git a/Upstream/Inc/upstream_interface_def.h b/Upstream/Inc/upstream_interface_def.h
index 3bb78b7..f4d0a23 100644
--- a/Upstream/Inc/upstream_interface_def.h
+++ b/Upstream/Inc/upstream_interface_def.h
@@ -60,7 +60,7 @@ InterfaceCommandMscTypeDef;
 typedef enum
 {
     COMMAND_HID_GET_REPORT,			//Returns HID report from device
-    COMMAND_HID_SET_REPORT          //Sends HID report to device. No reply or ack expected.
+    COMMAND_HID_SET_REPORT          //Sends HID report to device. Simple ack packet contains no data.
 }
 InterfaceCommandHidTypeDef;
 
diff --git a/Upstream/Src/upstream_hid.c b/Upstream/Src/upstream_hid.c
index a029524..ac89ff5 100644
--- a/Upstream/Src/upstream_hid.c
+++ b/Upstream/Src/upstream_hid.c
@@ -19,8 +19,8 @@
 UpstreamPacketTypeDef*          UpstreamHidPacket = NULL;
 UpstreamHidGetReportCallback    GetReportCallback = NULL;
 
-uint8_t     KeyboardOutDataAvailable = 0;
-uint8_t     KeyboardOutData[HID_KEYBOARD_OUTPUT_DATA_LEN];
+KeyboardOutStateTypeDef KeyboardOutDataState = KEYBOARD_OUT_STATE_IDLE;
+uint8_t                 KeyboardOutData[HID_KEYBOARD_OUTPUT_DATA_LEN];
 
 
 
@@ -36,7 +36,7 @@ void Upstream_HID_DeInit(void)
         UpstreamHidPacket = NULL;
     }
     GetReportCallback = NULL;
-    KeyboardOutDataAvailable = 0;
+    KeyboardOutDataState = KEYBOARD_OUT_STATE_IDLE;
 }
 
 
@@ -54,11 +54,31 @@ void Upstream_HID_GetNextInterruptReport(UpstreamHidGetReportCallback callback)
         return;
     }
 
-    //Just return if we already have an outstanding request
-    if (GetReportCallback != NULL)
+    if (callback != NULL)
     {
-        return;
+        //This means we were called by the host (normal operation)
+        if (KeyboardOutDataState == KEYBOARD_OUT_STATE_BUSY)
+        {
+            //Just save the callback, because we are still waiting for the OUT report to complete
+            GetReportCallback = callback;
+            return;
+        }
+        if (GetReportCallback != NULL)
+        {
+            //Just return if we already have an outstanding request
+            return;
+        }
+    }
+    else
+    {
+        //This means were called on OUT report completion
+        if (GetReportCallback == NULL)
+        {
+            //The host has not given us the callback yet, so we give up
+            return;
+        }
     }
+
     GetReportCallback = callback;
 
     //Release packet used for last transaction (if any)
@@ -175,7 +195,7 @@ void Upstream_HID_GetNextInterruptReportReceiveCallback(UpstreamPacketTypeDef* r
 
 
     //Check if we need to send OUT data to the keyboard before requesting next Interrupt IN data
-    if (KeyboardOutDataAvailable)
+    if (KeyboardOutDataState == KEYBOARD_OUT_STATE_DATA_READY)
     {
         Upstream_HID_ReallySendControlReport();
     }
@@ -203,7 +223,7 @@ void Upstream_HID_SendControlReport(UpstreamPacketTypeDef* packetToSend, uint8_t
     }
 
     //Save data until after the next interrupt data is received from Downstream
-    KeyboardOutDataAvailable = 1;
+    KeyboardOutDataState = KEYBOARD_OUT_STATE_DATA_READY;
     for (i = 0; i < HID_KEYBOARD_OUTPUT_DATA_LEN; i++)
     {
         KeyboardOutData[i] = packetToSend->Data[i];
@@ -217,7 +237,7 @@ void Upstream_HID_ReallySendControlReport(void)
     UpstreamPacketTypeDef* freePacket;
     uint32_t i;
 
-    KeyboardOutDataAvailable = 0;
+    KeyboardOutDataState = KEYBOARD_OUT_STATE_BUSY;
 
     freePacket = Upstream_GetFreePacketImmediately();
     if (freePacket == NULL) return;
@@ -232,10 +252,39 @@ void Upstream_HID_ReallySendControlReport(void)
     }
     freePacket->Data[0] &= ((1 << HID_KEYBOARD_MAX_LED) - 1);
 
-    if (Upstream_TransmitPacket(freePacket) != HAL_OK)
+    if (Upstream_TransmitPacket(freePacket) == HAL_OK)
+    {
+        Upstream_ReceivePacket(Upstream_HID_GetNextInterruptReportReceiveCallback);
+    }
+    else
     {
         Upstream_ReleasePacket(freePacket);
     }
 }
 
 
+
+void Upstream_HID_ReallySendControlReportReceiveCallback(UpstreamPacketTypeDef* receivedPacket)
+{
+    InterfaceCommandClassTypeDef activeClass;
+
+    activeClass = Upstream_StateMachine_CheckActiveClass();
+    if (activeClass != COMMAND_CLASS_HID_KEYBOARD)        //add classes here
+    {
+        UPSTREAM_STATEMACHINE_FREAKOUT;
+        return;
+    }
+
+    if (receivedPacket == NULL)
+    {
+        return;             //Just give up...
+    }
+
+    Upstream_ReleasePacket(receivedPacket);
+    KeyboardOutDataState = KEYBOARD_OUT_STATE_IDLE;
+
+    //If upstream host has already requested the next IN report data,
+    //this will send the request downstream.
+    Upstream_HID_GetNextInterruptReport(NULL);
+}
+