Problem with USB CDC settings and libraries for STM32F4

Question

I'm working in an embedded aplication for STM32F401RBT6 and I'm trying to establish a connection with the PC (Windows 10) but the device is not recognized by the system. The code that I generated by STMCubeMX and debugged by Atollic not works. I saw and try reproduce several examples, but anything works. In the code, I have all libraries that i think necessary.

I'm have this archives generated by STMCubeMX for the CDC comunication, but I'm newbie and I don't know what I have to modify on the code for the USB be recognized by the system. Someone can help me?

Answer 1

Inside USBD_CDC_Init(..) function there is a malloc function which allocates about 540 Bytes memory on the Heap.

This was not taken into account from CubeMX when code generated.

So, at least you must define the Heap size taking into account theese extra Bytes, to have the USB CDC port working.

Answer 2

Beside the point from Soup ( the failing malloc caused by a heap that is only 0x200 by default) some Windows version have a problem with the line coding in the example.

In the usbd_cdc_if.c you should add:

/* USER CODE BEGIN PRIVATE_VARIABLES */
USBD_CDC_LineCodingTypeDef LineCoding =
    {
    115200, /* baud rate*/
    0x00,   /* stop bits-1*/
    0x00,   /* parity - none*/
    0x08    /* nb. of bits 8*/
    };

And a little bit below

static int8_t CDC_Control_FS(uint8_t cmd, uint8_t* pbuf, uint16_t length)
.
.
.
case CDC_SET_LINE_CODING:
    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];

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;

So the host won't get undefined data if he tries to set the line coding.