ERE S n.c. DC485USB: Instruction Manual Revision: 1.0
Page 3 of 7
PWR line
: Operation
Active High
Equals to the
DTR
criteria of a RS-232 port
PWR line
: Voltages
0 – 5 Vdc
(2)
No load condition on PWR line
PWR line
: Currents
≤
± 8 mA
- incoming,
+
outgoing.
PWR line
: Impedances
440
Ω
Impedance of the protection circuitry.
Connecting cable
A type
plug
–
µ
USB B type
plug Standard cable, max. length 3 m (3.28 yd).
Temperature operating range
- 20 + 55 °C (-22°F
→
+158°F)
Mechanical dimensions
53
x
31
x
21.50 mm
2.086 x 1.22 x 0.846 inches
Overall dimensions with rubber feet.
Weight
18 g
0.635 oz. av.
Max weight with rubber feet.
NOTES:
(1)
After the
Start Bit
. Practically all format with
10
or
11 bits/word
are accepted.
(2)
Equals to the supply voltage outgoing from the USB Port. Normally it is
5 Vdc
.
All stated specifications are subjected to change without notice or obligation
1.2 CE
Conformity
.
The
DC485USB Converter
is
CE compliant
under the following directives and related modifications:
2006/95/CE “Low Voltage” Directive
2004/108/CE “ Electromagnetic Compatibility” Directive
2.0
Circuit description
.
The
DC485USB Converter
utilise the
FT232R
integrated circuit produced by FTDI. This integrated circuit allows the
implementation of a
VCP (Virtual COM Port)
in a device equipped with only the USB Port, such as a Personal Com-
puter. To install this VCP, the personal computer requires the
installation of a suitable Driver
that may be selected, as
function of the installed OS in the PC, into the Drivers Page of the FTDI website
www.ftdichip.com
The TTL input/output from the FT232 are connected to the RS-485 Interface chip, characterised by a low power
consumption and protected against overvoltages, followed by the overvoltages protection circuitry utilising the
transient voltage suppressors
.
The USB converter furnishes a
DTR criteria
that may be used as
ON/OFF switch
for the external device. As the serial
port lines, also this signal is protected against overvoltages.
A
Supply supervisor circuit
controls the
reset line
of the converter chip to avoid any malfunction due to supply
problems.
The whole device show a
current consumption lower than 100 mA
, therefore it
can be connected to any type of
USB
port, and it is
completely disabled
when the USB port enters in
Suspend Mode
, keeping the
Fail Safe
bias on
the RS- 485 lines and
reducing
the current consumption under
500
µ
A
.
3.0
Selection and Installation of the VCP Driver
.
Converter parameters
.
3.0.1 Selection and Installation of the VCP Driver
.
To operate correctly, the
DC485USB Converter
needs an appropriate driver that must be installed into the Personal
Computer. This driver can be downloaded from the FTDI website and installed into own PC. The FTDI allows the
selection of the more adequate driver as function of the used Operative System and the computer architecture. In all
cases we recommend the installation of the
stable version
of the driver, if a choice between it and a
Beta version
is
available, because the second could be
not fully compatible
with the own computer.
From the Home Page of th FTDI website select Drivers and, successively, VCP Drivers to enter in the related page. Into
the driver list select the one compatible with own computer and start the download to install it into the pc. Normally the
drivers are available in a
zipped file
with
.zip
extension.
For example with a Windows XP operative system the correct procedure is the following:
-
Download the selected driver and save it in a directory.
-
Unzip this file with an
unzip program
, such as Winzip or Winrar, and extract the files into a suitable directory,
such as
C:\FTDI Driver
, so that may be easy to find them when requested.
-
Connect the converter to an USB port and, as happens with any new hardware found, a dialogue box will be opened
by Windows to complete the installation procedure. The procedure asks the search of the related and, between the