CubeMX USB CDC VCP - Transmission problem

hello,

i am trying to send data to pc over the otg used as a virtual com port. The data is received with a terminal program (HTerm). In order to send data i am using the function CDC_Transmit_FS. For a basic test the string 'start' is sent to the pc. Therefor i use the following code. The code is implemented in the while loop of the int main function:

while(1)

{

if(((USBD_CDC_HandleTypeDef*)(hUsbDeviceFS.pClassData))->TxState==0)

{

while(CDC_Transmit_FS(((uint8_t*)&'start'),sizeof('start')) != USBD_OK);

}

}

This works and i can receive the data on the terminal program on my pc.

What doesn't work: If i try to send 'stop' after the 'start' string.

while(1)

{

if(((USBD_CDC_HandleTypeDef*)(hUsbDeviceFS.pClassData))->TxState==0)

{

while(CDC_Transmit_FS(((uint8_t*)&'start'),sizeof('start')) != USBD_OK);

}

if(((USBD_CDC_HandleTypeDef*)(hUsbDeviceFS.pClassData))->TxState==0)

{

while(CDC_Transmit_FS(((uint8_t*)&'stop'),sizeof('stop')) != USBD_OK);

}

}

what i hoped to receive is: start stop start stop start stop.... in an alternating order

but what i get is somehow confusing because now there is no order of the received data. I get start start stop start stop stop ...   start and stop are in different orders

Thank you for your help!