There are only three wires that need to be connected as illustrated in
Figure 5.7. The ground signals of the discovery board and uart bridge need
to be connected (these are labeled gnd) – there are multiple ground pins on
the discovery board all of which are electrically connected by the PCB. Thus,
only a single wire (black is traditional) is needed to tie the ground signals
together. You will need to connect the rx (tx) pin of USART1 to the tx (rx)
pin of the USB/uart