stmhal: Check CDC tx buffer has free space before filling with data.

1 files changed, 393 insertions, 553 deletions

diff --git a/stmhal/usbd_cdc_interface.c b/stmhal/usbd_cdc_interface.c
index 402fba2ce5..e0f387eb7e 100644
--- a/stmhal/usbd_cdc_interface.c
+++ b/stmhal/usbd_cdc_interface.c
@@ -1,553 +1,393 @@
-/**

-  ******************************************************************************

-  * @file    USB_Device/CDC_Standalone/Src/usbd_cdc_interface.c

-  * @author  MCD Application Team

-  * @version V1.0.1

-  * @date    26-February-2014

-  * @brief   Source file for USBD CDC interface

-  ******************************************************************************

-  * @attention

-  *

-  * <h2><center>&copy; COPYRIGHT(c) 2014 STMicroelectronics</center></h2>

-  *

-  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");

-  * You may not use this file except in compliance with the License.

-  * You may obtain a copy of the License at:

-  *

-  *        http://www.st.com/software_license_agreement_liberty_v2

-  *

-  * Unless required by applicable law or agreed to in writing, software 

-  * distributed under the License is distributed on an "AS IS" BASIS, 

-  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

-  * See the License for the specific language governing permissions and

-  * limitations under the License.

-  *

-  ******************************************************************************

-  */

-

-/* Includes ------------------------------------------------------------------*/

-#include <stdbool.h>

-#include "stm32f4xx_hal.h"

-#include "usbd_cdc.h"

-#include "usbd_cdc_interface.h"

-#include "pendsv.h"

-#include "usb.h"

-

-/** @addtogroup STM32_USB_OTG_DEVICE_LIBRARY

-  * @{

-  */

-

-/** @defgroup USBD_CDC 

-  * @brief usbd core module

-  * @{

-  */ 

-

-/* Private typedef -----------------------------------------------------------*/

-/* Private define ------------------------------------------------------------*/

-#define APP_RX_DATA_SIZE  1024 // I think this must be at least CDC_DATA_FS_OUT_PACKET_SIZE (was 2048)

-#define APP_TX_DATA_SIZE  1024 // I think this can be any value (was 2048)

-

-/* Private macro -------------------------------------------------------------*/

-/* Private variables ---------------------------------------------------------*/

-

-static uint8_t UserRxBuffer[APP_RX_DATA_SIZE]; // received data from USB OUT endpoint is stored in this buffer

-static uint16_t UserRxBufCur = 0; // points to next available character in UserRxBuffer

-static uint16_t UserRxBufLen = 0; // counts number of valid characters in UserRxBuffer

-

-static uint8_t UserTxBuffer[APP_TX_DATA_SIZE]; // data for USB IN endpoind is stored in this buffer

-static uint16_t UserTxBufPtrIn = 0; // increment this pointer modulo APP_TX_DATA_SIZE when new data is available

-static uint16_t UserTxBufPtrOut = 0; // increment this pointer modulo APP_TX_DATA_SIZE when data is drained

-

-static int user_interrupt_char = VCP_CHAR_NONE;

-static void *user_interrupt_data = NULL;

-

-/* TIM handler declaration */

-TIM_HandleTypeDef USBD_CDC_TimHandle;

-/* USB handler declaration */

-extern USBD_HandleTypeDef hUSBDDevice;

-

-/* Private function prototypes -----------------------------------------------*/

-static int8_t CDC_Itf_Init     (void);

-static int8_t CDC_Itf_DeInit   (void);

-static int8_t CDC_Itf_Control  (uint8_t cmd, uint8_t* pbuf, uint16_t length);

-static int8_t CDC_Itf_Receive  (uint8_t* pbuf, uint32_t *Len);

-

-static void Error_Handler(void);

-//static void ComPort_Config(void);

-static void TIM_Config(void);

-

-const USBD_CDC_ItfTypeDef USBD_CDC_fops = {

-    CDC_Itf_Init,

-    CDC_Itf_DeInit,

-    CDC_Itf_Control,

-    CDC_Itf_Receive

-};

-

-/* Private functions ---------------------------------------------------------*/

-

-/**

-  * @brief  CDC_Itf_Init

-  *         Initializes the CDC media low layer

-  * @param  None

-  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL

-  */

-static int8_t CDC_Itf_Init(void)

-{

-#if 0

-  /*##-1- Configure the UART peripheral ######################################*/

-  /* Put the USART peripheral in the Asynchronous mode (UART Mode) */

-  /* USART configured as follow:

-      - Word Length = 8 Bits

-      - Stop Bit    = One Stop bit

-      - Parity      = No parity

-      - BaudRate    = 115200 baud

-      - Hardware flow control disabled (RTS and CTS signals) */

-  UartHandle.Instance        = USARTx;

-  UartHandle.Init.BaudRate   = 115200;

-  UartHandle.Init.WordLength = UART_WORDLENGTH_8B;

-  UartHandle.Init.StopBits   = UART_STOPBITS_1;

-  UartHandle.Init.Parity     = UART_PARITY_NONE;

-  UartHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;

-  UartHandle.Init.Mode       = UART_MODE_TX_RX;

-  

-  if(HAL_UART_Init(&UartHandle) != HAL_OK)

-  {

-    /* Initialization Error */

-    Error_Handler();

-  }

-  

-  /*##-2- Put UART peripheral in IT reception process ########################*/

-  /* Any data received will be stored in "UserTxBuffer" buffer  */

-  if(HAL_UART_Receive_IT(&UartHandle, (uint8_t *)UserTxBuffer, 1) != HAL_OK)

-  {

-    /* Transfer error in reception process */

-    Error_Handler();

-  }

-#endif

-  

-  /*##-3- Configure the TIM Base generation  #################################*/

-  TIM_Config();

-  

-  /*##-4- Start the TIM Base generation in interrupt mode ####################*/

-  /* Start Channel1 */

-  if(HAL_TIM_Base_Start_IT(&USBD_CDC_TimHandle) != HAL_OK)

-  {

-    /* Starting Error */

-    Error_Handler();

-  }

-  

-  /*##-5- Set Application Buffers ############################################*/

-  USBD_CDC_SetTxBuffer(&hUSBDDevice, UserTxBuffer, 0);

-  USBD_CDC_SetRxBuffer(&hUSBDDevice, UserRxBuffer);

-

-    UserRxBufCur = 0;

-    UserRxBufLen = 0;

-  

-    user_interrupt_char = VCP_CHAR_NONE;

-    user_interrupt_data = NULL;

-

-  return (USBD_OK);

-}

-

-/**

-  * @brief  CDC_Itf_DeInit

-  *         DeInitializes the CDC media low layer

-  * @param  None

-  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL

-  */

-static int8_t CDC_Itf_DeInit(void)

-{

-#if 0

-  /* DeInitialize the UART peripheral */

-  if(HAL_UART_DeInit(&UartHandle) != HAL_OK)

-  {

-    /* Initialization Error */

-    Error_Handler();

-  }

-#endif

-  return (USBD_OK);

-}

-

-/**

-  * @brief  CDC_Itf_Control

-  *         Manage the CDC class requests

-  * @param  Cmd: Command code            

-  * @param  Buf: Buffer containing command data (request parameters)

-  * @param  Len: Number of data to be sent (in bytes)

-  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL

-  */

-static int8_t CDC_Itf_Control (uint8_t cmd, uint8_t* pbuf, uint16_t length)

-{ 

-  switch (cmd)

-  {

-  case CDC_SEND_ENCAPSULATED_COMMAND:

-    /* Add your code here */

-    break;

-

-  case CDC_GET_ENCAPSULATED_RESPONSE:

-    /* Add your code here */

-    break;

-

-  case CDC_SET_COMM_FEATURE:

-    /* Add your code here */

-    break;

-

-  case CDC_GET_COMM_FEATURE:

-    /* Add your code here */

-    break;

-

-  case CDC_CLEAR_COMM_FEATURE:

-    /* Add your code here */

-    break;

-

-  case CDC_SET_LINE_CODING:

-    #if 0

-    LineCoding.bitrate    = (uint32_t)(pbuf[0] | (pbuf[1] << 8) |\

-                            (pbuf[2] << 16) | (pbuf[3] << 24));

-    LineCoding.format     = pbuf[4];

-    LineCoding.paritytype = pbuf[5];

-    LineCoding.datatype   = pbuf[6];

-    

-    /* Set the new configuration */

-    ComPort_Config();

-    #endif

-    break;

-

-  case CDC_GET_LINE_CODING:

-    #if 0

-    pbuf[0] = (uint8_t)(LineCoding.bitrate);

-    pbuf[1] = (uint8_t)(LineCoding.bitrate >> 8);

-    pbuf[2] = (uint8_t)(LineCoding.bitrate >> 16);

-    pbuf[3] = (uint8_t)(LineCoding.bitrate >> 24);

-    pbuf[4] = LineCoding.format;

-    pbuf[5] = LineCoding.paritytype;

-    pbuf[6] = LineCoding.datatype;     

-    #endif

-    

-    /* Add your code here */

-    pbuf[0] = (uint8_t)(115200);

-    pbuf[1] = (uint8_t)(115200 >> 8);

-    pbuf[2] = (uint8_t)(115200 >> 16);

-    pbuf[3] = (uint8_t)(115200 >> 24);

-    pbuf[4] = 0; // stop bits (1)

-    pbuf[5] = 0; // parity (none)

-    pbuf[6] = 8; // number of bits (8)

-    break;

-

-  case CDC_SET_CONTROL_LINE_STATE:

-    /* Add your code here */

-    break;

-

-  case CDC_SEND_BREAK:

-     /* Add your code here */

-    break;    

-    

-  default:

-    break;

-  }

-  

-  return (USBD_OK);

-}

-

-/**

-  * @brief  TIM period elapsed callback

-  * @param  htim: TIM handle

-  * @retval None

-  */

-void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)

-{

-  uint32_t buffptr;

-  uint32_t buffsize;

-  

-  if(UserTxBufPtrOut != UserTxBufPtrIn)

-  {

-    if(UserTxBufPtrOut > UserTxBufPtrIn) /* rollback */

-    {

-      buffsize = APP_RX_DATA_SIZE - UserTxBufPtrOut;

-    }

-    else 

-    {

-      buffsize = UserTxBufPtrIn - UserTxBufPtrOut;

-    }

-    

-    buffptr = UserTxBufPtrOut;

-    

-    USBD_CDC_SetTxBuffer(&hUSBDDevice, (uint8_t*)&UserTxBuffer[buffptr], buffsize);

-    

-    if(USBD_CDC_TransmitPacket(&hUSBDDevice) == USBD_OK)

-    {

-      UserTxBufPtrOut += buffsize;

-      if (UserTxBufPtrOut == APP_RX_DATA_SIZE)

-      {

-        UserTxBufPtrOut = 0;

-      }

-    }

-  }

-}

-

-#if 0

-/**

-  * @brief  Rx Transfer completed callback

-  * @param  huart: UART handle

-  * @retval None

-  */

-void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)

-{

-  /* Increment Index for buffer writing */

-  UserTxBufPtrIn++;

-  

-  /* To avoid buffer overflow */

-  if(UserTxBufPtrIn == APP_RX_DATA_SIZE)

-  {

-    UserTxBufPtrIn = 0;

-  }

-  

-  /* Start another reception: provide the buffer pointer with offset and the buffer size */

-  HAL_UART_Receive_IT(huart, (uint8_t *)(UserTxBuffer + UserTxBufPtrIn), 1);

-}

-#endif

-

-/**

-  * @brief  CDC_Itf_DataRx

-  *         Data received over USB OUT endpoint is processed here.

-  * @param  Buf: Buffer of data received

-  * @param  Len: Number of data received (in bytes)

-  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL

-  * @note   The buffer we are passed here is just UserRxBuffer, so we are

-  *         free to modify it.

-  */

-static int8_t CDC_Itf_Receive(uint8_t* Buf, uint32_t *Len) {

-#if 0

-    // this sends the data over the UART using DMA

-    HAL_UART_Transmit_DMA(&UartHandle, Buf, *Len);

-#endif

-

-    if (user_interrupt_char == VCP_CHAR_NONE) {

-        // no special interrupt character

-        UserRxBufLen = *Len;

-

-    } else {

-        // filter out sepcial interrupt character from the buffer

-        bool char_found = false;

-        uint8_t *dest = Buf;

-        uint8_t *src = Buf;

-        uint8_t *buf_top = Buf + *Len;

-        for (; src < buf_top; src++) {

-            if (*src == user_interrupt_char) {

-                char_found = true;

-            } else {

-                if (char_found) {

-                    *dest = *src;

-                }

-                dest++;

-            }

-        }

-

-        // set length of remaining characters

-        UserRxBufLen = dest - Buf;

-

-        if (char_found) {

-            // raise exception when interrupts are finished

-            user_interrupt_char = VCP_CHAR_NONE;

-            pendsv_nlr_jump(user_interrupt_data);

-        }

-    }

-

-    // there are new characters at the start of the buffer, so point there

-    UserRxBufCur = 0;

-

-    if (UserRxBufLen == 0) {

-        // initiate next USB packet transfer now that UserRxBuffer has been drained

-        USBD_CDC_ReceivePacket(&hUSBDDevice);

-    }

-

-    return (USBD_OK);

-}

-

-void USBD_CDC_SetInterrupt(int chr, void *data) {

-    user_interrupt_char = chr;

-    user_interrupt_data = data;

-}

-

-void USBD_CDC_Tx(const char *str, uint32_t len) {

-    for (int i = 0; i < len; i++) {

-        UserTxBuffer[UserTxBufPtrIn] = str[i];

-        UserTxBufPtrIn = (UserTxBufPtrIn + 1) & (APP_TX_DATA_SIZE - 1);

-    }

-}

-

-int USBD_CDC_RxNum(void) {

-    return UserRxBufLen - UserRxBufCur;

-}

-

-int USBD_CDC_RxGet(void) {

-    // wait for buffer to have at least 1 character in it

-    while (USBD_CDC_RxNum() == 0) {

-        __WFI();

-    }

-

-    // get next character

-    int c = UserRxBuffer[UserRxBufCur++];

-    if (UserRxBufCur >= UserRxBufLen) {

-        // initiate next USB packet transfer now that UserRxBuffer has been drained

-        USBD_CDC_ReceivePacket(&hUSBDDevice);

-    }

-    return c;

-}

-

-#if 0

-/**

-  * @brief  Tx Transfer completed callback

-  * @param  huart: UART handle

-  * @retval None

-  */

-void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)

-{

-  /* Initiate next USB packet transfer once UART completes transfer (transmitting data over Tx line) */

-  USBD_CDC_ReceivePacket(&hUSBDDevice);

-}

-

-/**

-  * @brief  ComPort_Config

-  *         Configure the COM Port with the parameters received from host.

-  * @param  None.

-  * @retval None.

-  * @note   When a configuration is not supported, a default value is used.

-  */

-static void ComPort_Config(void)

-{

-  if(HAL_UART_DeInit(&UartHandle) != HAL_OK)

-  {

-    /* Initialization Error */

-    Error_Handler();

-  }

-  

-  /* set the Stop bit */

-  switch (LineCoding.format)

-  {

-  case 0:

-    UartHandle.Init.StopBits = UART_STOPBITS_1;

-    break;

-  case 2:

-    UartHandle.Init.StopBits = UART_STOPBITS_2;

-    break;

-  default :

-    UartHandle.Init.StopBits = UART_STOPBITS_1;

-    break;

-  }

-  

-  /* set the parity bit*/

-  switch (LineCoding.paritytype)

-  {

-  case 0:

-    UartHandle.Init.Parity = UART_PARITY_NONE;

-    break;

-  case 1:

-    UartHandle.Init.Parity = UART_PARITY_ODD;

-    break;

-  case 2:

-    UartHandle.Init.Parity = UART_PARITY_EVEN;

-    break;

-  default :

-    UartHandle.Init.Parity = UART_PARITY_NONE;

-    break;

-  }

-  

-  /*set the data type : only 8bits and 9bits is supported */

-  switch (LineCoding.datatype)

-  {

-  case 0x07:

-    /* With this configuration a parity (Even or Odd) must be set */

-    UartHandle.Init.WordLength = UART_WORDLENGTH_8B;

-    break;

-  case 0x08:

-    if(UartHandle.Init.Parity == UART_PARITY_NONE)

-    {

-      UartHandle.Init.WordLength = UART_WORDLENGTH_8B;

-    }

-    else 

-    {

-      UartHandle.Init.WordLength = UART_WORDLENGTH_9B;

-    }

-    

-    break;

-  default :

-    UartHandle.Init.WordLength = UART_WORDLENGTH_8B;

-    break;

-  }

-  

-  UartHandle.Init.BaudRate = LineCoding.bitrate;

-  UartHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;

-  UartHandle.Init.Mode       = UART_MODE_TX_RX;

-  

-  if(HAL_UART_Init(&UartHandle) != HAL_OK)

-  {

-    /* Initialization Error */

-    Error_Handler();

-  }

-

-  /* Start reception: provide the buffer pointer with offset and the buffer size */

-  HAL_UART_Receive_IT(&UartHandle, (uint8_t *)(UserTxBuffer + UserTxBufPtrIn), 1);

-}

-#endif

-

-/**

-  * @brief  TIM_Config: Configure TIMx timer

-  * @param  None.

-  * @retval None.

-  */

-static void TIM_Config(void)

-{  

-  /* Set TIMx instance */

-  USBD_CDC_TimHandle.Instance = USBD_CDC_TIMx;

-  

-  /* Initialize TIM3 peripheral as follow:

-       + Period = 10000 - 1

-       + Prescaler = ((SystemCoreClock/2)/10000) - 1

-       + ClockDivision = 0

-       + Counter direction = Up

-  */

-  USBD_CDC_TimHandle.Init.Period = (USBD_CDC_POLLING_INTERVAL*1000) - 1;

-  USBD_CDC_TimHandle.Init.Prescaler = 84-1;

-  USBD_CDC_TimHandle.Init.ClockDivision = 0;

-  USBD_CDC_TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;

-  if(HAL_TIM_Base_Init(&USBD_CDC_TimHandle) != HAL_OK)

-  {

-    /* Initialization Error */

-    Error_Handler();

-  }

-}

-

-#if 0

-/**

-  * @brief  UART error callbacks

-  * @param  UartHandle: UART handle

-  * @retval None

-  */

-void HAL_UART_ErrorCallback(UART_HandleTypeDef *UartHandle)

-{

-  /* Transfer error occured in reception and/or transmission process */

-  Error_Handler();

-}

-#endif

-

-/**

-  * @brief  This function is executed in case of error occurrence.

-  * @param  None

-  * @retval None

-  */

-static void Error_Handler(void)

-{

-  /* Add your own code here */

-}

-

-/**

-  * @}

-  */ 

-

-/**

-  * @}

-  */ 

-

-/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

-

+/**
+  ******************************************************************************
+  * @file    USB_Device/CDC_Standalone/Src/usbd_cdc_interface.c
+  * @author  MCD Application Team
+  * @version V1.0.1
+  * @date    26-February-2014
+  * @brief   Source file for USBD CDC interface
+  ******************************************************************************
+  * @attention
+  *
+  * <h2><center>&copy; COPYRIGHT(c) 2014 STMicroelectronics</center></h2>
+  *
+  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
+  * You may not use this file except in compliance with the License.
+  * You may obtain a copy of the License at:
+  *
+  *        http://www.st.com/software_license_agreement_liberty_v2
+  *
+  * Unless required by applicable law or agreed to in writing, software 
+  * distributed under the License is distributed on an "AS IS" BASIS, 
+  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  * See the License for the specific language governing permissions and
+  * limitations under the License.
+  *
+  ******************************************************************************
+  */
+
+/* Includes ------------------------------------------------------------------*/
+#include <stdbool.h>
+#include "stm32f4xx_hal.h"
+#include "usbd_cdc.h"
+#include "usbd_cdc_interface.h"
+#include "pendsv.h"
+#include "usb.h"
+
+/* Private typedef -----------------------------------------------------------*/
+/* Private define ------------------------------------------------------------*/
+#define APP_RX_DATA_SIZE  1024 // I think this must be at least CDC_DATA_FS_OUT_PACKET_SIZE (was 2048)
+#define APP_TX_DATA_SIZE  1024 // I think this can be any value (was 2048)
+
+/* Private macro -------------------------------------------------------------*/
+/* Private variables ---------------------------------------------------------*/
+
+static uint8_t UserRxBuffer[APP_RX_DATA_SIZE]; // received data from USB OUT endpoint is stored in this buffer
+static uint16_t UserRxBufCur = 0; // points to next available character in UserRxBuffer
+static uint16_t UserRxBufLen = 0; // counts number of valid characters in UserRxBuffer
+
+static uint8_t UserTxBuffer[APP_TX_DATA_SIZE]; // data for USB IN endpoind is stored in this buffer
+static uint16_t UserTxBufPtrIn = 0; // increment this pointer modulo APP_TX_DATA_SIZE when new data is available
+static uint16_t UserTxBufPtrOut = 0; // increment this pointer modulo APP_TX_DATA_SIZE when data is drained
+
+static int user_interrupt_char = VCP_CHAR_NONE;
+static void *user_interrupt_data = NULL;
+
+/* TIM handler declaration */
+TIM_HandleTypeDef USBD_CDC_TimHandle;
+/* USB handler declaration */
+extern USBD_HandleTypeDef hUSBDDevice;
+
+/* Private function prototypes -----------------------------------------------*/
+static int8_t CDC_Itf_Init     (void);
+static int8_t CDC_Itf_DeInit   (void);
+static int8_t CDC_Itf_Control  (uint8_t cmd, uint8_t* pbuf, uint16_t length);
+static int8_t CDC_Itf_Receive  (uint8_t* pbuf, uint32_t *Len);
+
+static void TIM_Config(void);
+
+const USBD_CDC_ItfTypeDef USBD_CDC_fops = {
+    CDC_Itf_Init,
+    CDC_Itf_DeInit,
+    CDC_Itf_Control,
+    CDC_Itf_Receive
+};
+
+/* Private functions ---------------------------------------------------------*/
+
+/**
+  * @brief  CDC_Itf_Init
+  *         Initializes the CDC media low layer
+  * @param  None
+  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
+  */
+static int8_t CDC_Itf_Init(void)
+{
+#if 0
+  /*##-1- Configure the UART peripheral ######################################*/
+  /* Put the USART peripheral in the Asynchronous mode (UART Mode) */
+  /* USART configured as follow:
+      - Word Length = 8 Bits
+      - Stop Bit    = One Stop bit
+      - Parity      = No parity
+      - BaudRate    = 115200 baud
+      - Hardware flow control disabled (RTS and CTS signals) */
+  UartHandle.Instance        = USARTx;
+  UartHandle.Init.BaudRate   = 115200;
+  UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
+  UartHandle.Init.StopBits   = UART_STOPBITS_1;
+  UartHandle.Init.Parity     = UART_PARITY_NONE;
+  UartHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;
+  UartHandle.Init.Mode       = UART_MODE_TX_RX;
+  
+  if(HAL_UART_Init(&UartHandle) != HAL_OK)
+  {
+    /* Initialization Error */
+    Error_Handler();
+  }
+  
+  /*##-2- Put UART peripheral in IT reception process ########################*/
+  /* Any data received will be stored in "UserTxBuffer" buffer  */
+  if(HAL_UART_Receive_IT(&UartHandle, (uint8_t *)UserTxBuffer, 1) != HAL_OK)
+  {
+    /* Transfer error in reception process */
+    Error_Handler();
+  }
+#endif
+  
+  /*##-3- Configure the TIM Base generation  #################################*/
+  TIM_Config();
+  
+  /*##-4- Start the TIM Base generation in interrupt mode ####################*/
+  /* Start Channel1 */
+  if(HAL_TIM_Base_Start_IT(&USBD_CDC_TimHandle) != HAL_OK)
+  {
+    /* Starting Error */
+  }
+  
+  /*##-5- Set Application Buffers ############################################*/
+  USBD_CDC_SetTxBuffer(&hUSBDDevice, UserTxBuffer, 0);
+  USBD_CDC_SetRxBuffer(&hUSBDDevice, UserRxBuffer);
+
+    UserRxBufCur = 0;
+    UserRxBufLen = 0;
+  
+    user_interrupt_char = VCP_CHAR_NONE;
+    user_interrupt_data = NULL;
+
+  return (USBD_OK);
+}
+
+/**
+  * @brief  CDC_Itf_DeInit
+  *         DeInitializes the CDC media low layer
+  * @param  None
+  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
+  */
+static int8_t CDC_Itf_DeInit(void)
+{
+#if 0
+  /* DeInitialize the UART peripheral */
+  if(HAL_UART_DeInit(&UartHandle) != HAL_OK)
+  {
+    /* Initialization Error */
+  }
+#endif
+  return (USBD_OK);
+}
+
+/**
+  * @brief  CDC_Itf_Control
+  *         Manage the CDC class requests
+  * @param  Cmd: Command code            
+  * @param  Buf: Buffer containing command data (request parameters)
+  * @param  Len: Number of data to be sent (in bytes)
+  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
+  */
+static int8_t CDC_Itf_Control (uint8_t cmd, uint8_t* pbuf, uint16_t length)
+{ 
+  switch (cmd)
+  {
+  case CDC_SEND_ENCAPSULATED_COMMAND:
+    /* Add your code here */
+    break;
+
+  case CDC_GET_ENCAPSULATED_RESPONSE:
+    /* Add your code here */
+    break;
+
+  case CDC_SET_COMM_FEATURE:
+    /* Add your code here */
+    break;
+
+  case CDC_GET_COMM_FEATURE:
+    /* Add your code here */
+    break;
+
+  case CDC_CLEAR_COMM_FEATURE:
+    /* Add your code here */
+    break;
+
+  case CDC_SET_LINE_CODING:
+    #if 0
+    LineCoding.bitrate    = (uint32_t)(pbuf[0] | (pbuf[1] << 8) |\
+                            (pbuf[2] << 16) | (pbuf[3] << 24));
+    LineCoding.format     = pbuf[4];
+    LineCoding.paritytype = pbuf[5];
+    LineCoding.datatype   = pbuf[6];
+    
+    /* Set the new configuration */
+    #endif
+    break;
+
+  case CDC_GET_LINE_CODING:
+    #if 0
+    pbuf[0] = (uint8_t)(LineCoding.bitrate);
+    pbuf[1] = (uint8_t)(LineCoding.bitrate >> 8);
+    pbuf[2] = (uint8_t)(LineCoding.bitrate >> 16);
+    pbuf[3] = (uint8_t)(LineCoding.bitrate >> 24);
+    pbuf[4] = LineCoding.format;
+    pbuf[5] = LineCoding.paritytype;
+    pbuf[6] = LineCoding.datatype;     
+    #endif
+    
+    /* Add your code here */
+    pbuf[0] = (uint8_t)(115200);
+    pbuf[1] = (uint8_t)(115200 >> 8);
+    pbuf[2] = (uint8_t)(115200 >> 16);
+    pbuf[3] = (uint8_t)(115200 >> 24);
+    pbuf[4] = 0; // stop bits (1)
+    pbuf[5] = 0; // parity (none)
+    pbuf[6] = 8; // number of bits (8)
+    break;
+
+  case CDC_SET_CONTROL_LINE_STATE:
+    /* Add your code here */
+    break;
+
+  case CDC_SEND_BREAK:
+     /* Add your code here */
+    break;    
+    
+  default:
+    break;
+  }
+  
+  return (USBD_OK);
+}
+
+/**
+  * @brief  TIM period elapsed callback
+  * @param  htim: TIM handle
+  * @retval None
+  */
+void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
+{
+  uint32_t buffptr;
+  uint32_t buffsize;
+  
+  if(UserTxBufPtrOut != UserTxBufPtrIn)
+  {
+    if(UserTxBufPtrOut > UserTxBufPtrIn) /* rollback */
+    {
+      buffsize = APP_RX_DATA_SIZE - UserTxBufPtrOut;
+    }
+    else 
+    {
+      buffsize = UserTxBufPtrIn - UserTxBufPtrOut;
+    }
+    
+    buffptr = UserTxBufPtrOut;
+    
+    USBD_CDC_SetTxBuffer(&hUSBDDevice, (uint8_t*)&UserTxBuffer[buffptr], buffsize);
+    
+    if(USBD_CDC_TransmitPacket(&hUSBDDevice) == USBD_OK)
+    {
+      UserTxBufPtrOut += buffsize;
+      if (UserTxBufPtrOut == APP_RX_DATA_SIZE)
+      {
+        UserTxBufPtrOut = 0;
+      }
+    }
+  }
+}
+
+/**
+  * @brief  CDC_Itf_DataRx
+  *         Data received over USB OUT endpoint is processed here.
+  * @param  Buf: Buffer of data received
+  * @param  Len: Number of data received (in bytes)
+  * @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
+  * @note   The buffer we are passed here is just UserRxBuffer, so we are
+  *         free to modify it.
+  */
+static int8_t CDC_Itf_Receive(uint8_t* Buf, uint32_t *Len) {
+#if 0
+    // this sends the data over the UART using DMA
+    HAL_UART_Transmit_DMA(&UartHandle, Buf, *Len);
+#endif
+
+    if (user_interrupt_char == VCP_CHAR_NONE) {
+        // no special interrupt character
+        UserRxBufLen = *Len;
+
+    } else {
+        // filter out sepcial interrupt character from the buffer
+        bool char_found = false;
+        uint8_t *dest = Buf;
+        uint8_t *src = Buf;
+        uint8_t *buf_top = Buf + *Len;
+        for (; src < buf_top; src++) {
+            if (*src == user_interrupt_char) {
+                char_found = true;
+            } else {
+                if (char_found) {
+                    *dest = *src;
+                }
+                dest++;
+            }
+        }
+
+        // set length of remaining characters
+        UserRxBufLen = dest - Buf;
+
+        if (char_found) {
+            // raise exception when interrupts are finished
+            user_interrupt_char = VCP_CHAR_NONE;
+            pendsv_nlr_jump(user_interrupt_data);
+        }
+    }
+
+    // there are new characters at the start of the buffer, so point there
+    UserRxBufCur = 0;
+
+    if (UserRxBufLen == 0) {
+        // initiate next USB packet transfer now that UserRxBuffer has been drained
+        USBD_CDC_ReceivePacket(&hUSBDDevice);
+    }
+
+    return (USBD_OK);
+}
+
+void USBD_CDC_SetInterrupt(int chr, void *data) {
+    user_interrupt_char = chr;
+    user_interrupt_data = data;
+}
+
+void USBD_CDC_Tx(const char *str, uint32_t len) {
+    for (int i = 0; i < len; i++) {
+        uint timeout = 200;
+        while (UserTxBufPtrIn + 1 == UserTxBufPtrOut) {
+            if (timeout-- == 0) {
+                break;
+            }
+            HAL_Delay(1);
+        }
+        UserTxBuffer[UserTxBufPtrIn] = str[i];
+        UserTxBufPtrIn = (UserTxBufPtrIn + 1) & (APP_TX_DATA_SIZE - 1);
+    }
+}
+
+int USBD_CDC_RxNum(void) {
+    return UserRxBufLen - UserRxBufCur;
+}
+
+int USBD_CDC_RxGet(void) {
+    // wait for buffer to have at least 1 character in it
+    while (USBD_CDC_RxNum() == 0) {
+        __WFI();
+    }
+
+    // get next character
+    int c = UserRxBuffer[UserRxBufCur++];
+    if (UserRxBufCur >= UserRxBufLen) {
+        // initiate next USB packet transfer now that UserRxBuffer has been drained
+        USBD_CDC_ReceivePacket(&hUSBDDevice);
+    }
+    return c;
+}
+
+/**
+  * @brief  TIM_Config: Configure TIMx timer
+  * @param  None.
+  * @retval None.
+  */
+static void TIM_Config(void)
+{  
+  /* Set TIMx instance */
+  USBD_CDC_TimHandle.Instance = USBD_CDC_TIMx;
+  
+  /* Initialize TIM3 peripheral as follow:
+       + Period = 10000 - 1
+       + Prescaler = ((SystemCoreClock/2)/10000) - 1
+       + ClockDivision = 0
+       + Counter direction = Up
+  */
+  USBD_CDC_TimHandle.Init.Period = (USBD_CDC_POLLING_INTERVAL*1000) - 1;
+  USBD_CDC_TimHandle.Init.Prescaler = 84-1;
+  USBD_CDC_TimHandle.Init.ClockDivision = 0;
+  USBD_CDC_TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
+  if(HAL_TIM_Base_Init(&USBD_CDC_TimHandle) != HAL_OK)
+  {
+    /* Initialization Error */
+  }
+}