Posted on June 08, 2016 at 19:10Folks, I made some progress with CubeF0 and USB CDC class to get printf working. However, no characters appear on the hyper-term. The code roughly looks like:
USBD_HandleTypeDef USBD_Device;
extern UART_HandleTypeDef UartHandle;
void main(void)
{
uint8_t ch = 'a';
HAL_Init();
SystemClock_Config();
/* Init Device Library */
USBD_Init(&USBD_Device, &VCP_Desc, 0);
/* Add Supported Class */
USBD_RegisterClass(&USBD_Device, &USBD_CDC);
/* Add CDC Interface Class */
USBD_CDC_RegisterInterface(&USBD_Device, &USBD_CDC_fops);
/* Start Device Process */
USBD_Start(&USBD_Device);
while (1) {
status = HAL_UART_Transmit(&UartHandle, (uint8_t *)&ch, 1, 10);
}
}
However, nothing comes out on the Hyper-terminal connected on Windows. The HAL_Transmit_UART is going through but I fear that somehow the UART transmit data struct is not connected to the USB CDC class buffer and/or some DMA issue.
I don't want to use DMA but not sure how to just be in polling mode and if the UART (huart->Instance->TDR) in stmf0xx_hal_uart.c is really giving the character to the CDC.
I think that USB CDC class transmits a packet in the USBD_CDC_TransmitPacket() function where it calls
USBD_LL_Transmit(pdev, CDC_IN_EP, hcdc->TxBuffer, hcdc->TxLength);
Do I instead need to use HAL_UART_Transmit_IT() to transmit in interrupt mode for USB to recognize that data is pending? Otherwise I don't see how the HAL_UART_Transmit() connects to USB CDC. The _IT() version seems to connect via the UserTxBuffer[].
Any pointers in making progress will help me. Thanks.
