STM32 Open Bootloader USB I/Fbug

[WallaceOwenPB]

In attempting to figure out how to stay in the bootloader loop while exchanging packets with the USB DFU tool I came across as what looks like an unintentionally undeleted line of code.

Here is the code:

static void OPENBL_USART_Go(void)
{
  uint32_t address;
  uint32_t mem_area;

  /* Check memory protection then send adequate response */
  if (OPENBL_MEM_GetReadOutProtectionStatus() != RESET)
  {
    OPENBL_USART_SendByte(NACK_BYTE);
  }
  else
  {
    OPENBL_USART_SendByte(ACK_BYTE);

    /* Get memory address */
    if (OPENBL_USART_GetAddress(&address) == NACK_BYTE)
    {
      OPENBL_USART_SendByte(NACK_BYTE);
    }
    else
    {
      /* Check if received address is valid or not */
      mem_area = OPENBL_MEM_GetAddressArea(address);

      if ((mem_area != FLASH_AREA) && (mem_area != RAM_AREA))
      {
        OPENBL_USART_SendByte(NACK_BYTE);
      }
      else
      {
        /* If the jump address is valid then send ACK */
        OPENBL_USART_SendByte(ACK_BYTE);

        OPENBL_MEM_JumpToAddress(address);
      }
    }
  }
}

It looks like the statement on line 13 should be deleted.  If we don't it's going to send both an ack and either an ack or a nak, for one received message.  This is in the OpenBootloader repo, in the ST-Micro supplied file Source/OpenBootloader/Middlewares/ST/OpenBootloader/Modules/USART/openbl_usart_cmd.c

[TDK]

That particular ACK acknowledges protection is not active and the host can send the address. It's not a bug. It's in the UART protocol document here:

Multiple ACKs can be and often are within the same command.

cd00264342-usart-protocol-used-in-the-stm32-bootloader-stmicroelectronics.pdf