This logic level serial interface
is based on the FTDI FT232RL
converter and allows direct connection from a PC to an embedded processor
with logic level and polarity
compatibility, i.e. idle state is 1 and active state is 0. This is especially useful when debugging serial communications
directly from the target processor as well as allowing the elimination
of RS232 charge pump and driver circuits where the target serial interface is
only used for
programming etc, but not intended for regular connection to a PC.
- Embedded processor logic polarity compatibility: Idle state is logic high, start bit is logic
low (RS232 PC signal idle state is -12V and active state is +12V).
- The logic voltage level shifting is set by the
voltage at VIO
(Pin-2) and can range from 1.8V to 5.5V. Leave the jumper out when using an externally supplied
interface voltage.
- Internal 3.3V (10mA) and 5.0V (50mA) supplies can
be used externally and are present at VIO (Pin-2) when the jumper is
installed in one of the two positions.
- The FTDI
VCP
(Virtual Com Port) or
D2XX
(Direct Driver) drivers are available from the
FTDI website for
most operating systems. The VCP driver makes the serial interface look like a
standard COM port and is the first choice for most users. When
it enumerates, the USB driver selects the next free port number which
is keyed to the serial number of the FTDI chip and the physical port
it was plugged into, to
change the port setting to a specific one in Windows, go to the
hardware manager and force it to the number desired (Provided the new
number is actually a currently free port!).
- Find the active serial ports with this
utility:
Portlist.
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