Problem: If enabling partial return when using the driver in blocking mode, a call to UART_read will not return data already available in the ring buffer unless it is the number of bytes requested or any other data is received. If operating in callback mode, a call to UART_read will return already available data without the need to receive additional data. This problem occurs because we inside UART_read take the decision to start and pend for additional data instead if simply returning what data was already available. As a RX timeout will not occur unless data was received, the blocking semaphore will not be released by the driver. Proposed solution: Do a partial return check for blocking mode similar to what we do for callback mode.