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USB CDC communication


Hi all,

I am trying to USB CDC communication with my STM32 nucleo board. I want to send consecutive numbers and verify that they are consecutive and calculate the data rate.

I obtain errors, non consecutive numbers (irregularly), when I increase the amount of bytes I send. What can I do to solve this problem?


This is the code that I am using to send consecutive numbers:

uint32_t data[32];

USBD_StatusTypeDef status = 0 ;
while (1)

for (uint16_t i=0; i<32; i++)
status = USBD_FAIL;
while (status != USBD_OK){
status = CDC_Transmit_FS(data, sizeof(data));



Pavel A.
Evangelist III

Do you understand how USB works that  CDC_Transmit_FS needs time to complete? You cannot send a new data until the previous one is sent out. Also, mind the packet size specified for the USB endpoint, are you sending too short packets?