STM32F407 VCP Freertos recive data problem

[Muhammed Güler]

I'm trying to make a vcp implementation with STM32f407 and freertos.

I have no problem sending data from STM to my pc.

When I send data from PC to STM, when I send a few tens of bytes of data, the CDC_Receive_FS function is triggered several times and I cannot receive any processable data.

I tried to write a loopback application for testing.

I have edited the following codes in usbd_cdc_if.c file, one of the codes produced by CubeMX.

USBD_CDC_LineCodingTypeDef LineCoding =

{

115200, / * baud rate * /

0x00, / * stop bits-1 * /

0x00, / * parity - none * /

0x08 / * nb. of bits 8 * /

};

.....

static int8_t CDC_Control_FS (uint8_t cmd, uint8_t * pbuf, uint16_t length)

{

/ * USER CODE BEGIN 5 * /

switch (cmd)

{

case CDC_SEND_ENCAPSULATED_COMMAND:

break;

case CDC_GET_ENCAPSULATED_RESPONSE:

break;

case CDC_SET_COMM_FEATURE:

break;

case CDC_GET_COMM_FEATURE:

break;

case CDC_CLEAR_COMM_FEATURE:

break;

/ ************************************************* ****************************** /

/ * Line Coding Structure * /

/ * ------------------------------------------------ ----------------------------- * /

/ * Offset | Field | You | Value | Description * /

/ * 0 | dwDTERate | 4 | Number | Data terminal rate, in bits per second * /

/ * 4 | bCharFormat | 1 | Number | Stop bits * /

/ * 0 - 1 Stop bit * /

/ * 1 - 1.5 Stop bits * /

/ * 2 - 2 Stop bits * /

/ * 5 | bParityType | 1 | Number | Parity * /

/ * 0 - None * /

/ * 1 - Odd * /

/ * 2 - Even * /

/ * 3 - Mark * /

/ * 4 - Space * /

/ * 6 | bDataBits | 1 | Number Data bits (5, 6, 7, 8 or 16). * /

/ ************************************************* ****************************** /

case CDC_SET_LINE_CODING:

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

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

LineCoding.format = pbuf [4];

LineCoding.paritytype = pbuf [5];

LineCoding.datatype = pbuf [6];

/ * Set the new configuration * /

// ComPort_Config ();

break;

case CDC_GET_LINE_CODING:

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;

break;

case CDC_SET_CONTROL_LINE_STATE:

break;

case CDC_SEND_BREAK:

break;

default:

break;

}

return (USBD_OK);

/ * USER CODE END 5 * /

}

static int8_t CDC_Receive_FS (uint8_t * Buf, uint32_t * Len)

{

/ * USER CODE BEGIN 6 * /

USBD_CDC_SetRxBuffer (& hUsbDeviceFS, & Buf [0]);

USBD_CDC_ReceivePacket (& hUsbDeviceFS);

CDC_Transmit_FS (Buf, Len)); //send back incoming data

return (USBD_OK);

/ * USER CODE END 6 * /

}

When I send a File from Serial port to STM something goes back like the following

Copyright (cf ***********) 2020 ST ´Sight (cf *********** Microelectronics.

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* r *********** ght All ri „nics.

* r *********** s reserved. </ cente "Q *********** r> </h2>

 C „/ cente" Q *********** *

 * This softw ™ *********** are compon * softw ™ *********** e € �?compon * softw ™ ******* **** nt icompon * softw ™ *********** s licensed by ST un7 *********** der Ultimate Liberty ******* **** license

 * SLAËVL *********** 00ê [nape

 * SLAËVL *********** 44, the "^ & * SLAËVL *********** License"; ] * SLAËVL *********** You may not use th *********** is file EDGE use th ******** *** xcept in compliance w T ******* ith

 * tb§pliance w T ******* he License. You may obtain a *** copy of the açemay obtain a *** License a6 açemay obtain a *** t:

 * NÛ openemay obtain a *** şàobtain a *** wá şàobtain a *** ww.st.com/SLA0(Û shoobtain a *** 044

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Does anyone know how I can fix this situation

[Pavel A.]

In the CDC_Receive_FS function you cannot just call CDC_Transmit_FS. It cannot be called only if the input pipe is busy.

And it becomes busy until the host turns around and sends IN token.

Add some buffering to your loopback test.

-- pa