UM-0085-B09
DT80 Range User Manual
Page 193
RG
Figure 76: Determining USB COM port number in Device Manager
Note:
DtUsb must still be installed (but not running) in order to use the USB port in direct serial mode. If it is not installed then the DT80
will not be recognised and a COM port will not be assigned to it.
Sleep Mode
If the DT80 enters low power sleep mode then its USB interface will be reset. To the host computer, it will look like the
USB cable has been unplugged, so the configured COM port will disappear.
When the DT80 wakes, the PC will detect that a USB device has been connected, and re-create the COM port. The
application that was using the COM port will, however, most likely not automatically re-connect. For example,
DeTransfer
and DeLogger will require you to manually re-establish a connection.
For this reason it is recommended that the logger not be allowed to go to sleep while the USB cable is connected. By
default, low power sleep mode is automatically disabled if a USB cable is connected.
RS-232 Communications
Not applicable to DT8xM
Direct RS-232 Connection
For applications where the DT80 is to be directly connected to a nearby computer, USB is normally the preferred
communications medium. However, you may wish to use a direct RS232 connection if:
•
your computer has no available USB ports
•
you have a DT82 model, which does not have a USB port
•
you need the DT80 to go into low power sleep mode between scans, and you want to continue to receive real-
time data returns; or you want to be able to wake the DT80 by sending a character (See
)
•
the required cable length is longer than about 5 metres.
Normally the DT80's
host RS232
port
is used when making a direct RS232 connection to a host computer.
However the
serial sensor
port
can also be used.
To set up a direct RS232 connection you will need a "cross-over", or "null-modem" cable. Suitable cables may be
ordered for this purpose (dataTaker product code IBM-6 for host port connection, or CAB-015 for serial sensor port). See
for wiring information.
It is also possible to use a simpler 3-wire cable (
RxD
,
TxD
and
GND
) although this will mean that hardware flow control
is not possible.
If your computer has no RS232 ports (as is the case for many laptop models) a USB to serial adapter may be used.
Cable Length
Although the RS 232 standard specifies a cable of not more than 4 metres (15 feet), longer cables can be used. It’s
possible to use RS 232 cable runs of 100 metres or more, but to achieve reasonably error-free communication these
generally need to have heavier wires and a slower baud rate may be necessary.
RS-232 Flow Control
Flow control
(or
handshaking
) is the means by which communicating devices (such as the DT80 and a host computer)
control each other’s transmission of characters to avoid data loss. The receiver uses flow control to disable transmissions
by the sender if the receiver’s input buffer is at risk of overflowing and thereby losing data.
The DT80 supports all methods of flow control:
•
Software flow control (also known as XON/XOFF flow control)
•
Hardware flow control (also known as RTS/CTS flow control)
•
No flow control