Novatel OEM7 - Communications with the Receiver; Serial Ports

Chapter 3 OEM7 Receiver Operation
OEM7 Installation and Operation User Manual v1 41
3.1 Communications with the Receiver
Communication is established with the receiver using a data terminal or computer connected to
one of the receiver’s communications ports using a null modem, USB or Ethernet cable.
When connected to the receiver, enter commands directly from the terminal or through terminal
emulation software (such as NovAtel Connect or HyperTerminal) on a computer.
NovAtel Connect version 2.0 or greater is required for OEM7 receivers. Download
the latest NovAtel Connect PC Utilities suite of software and documentation,
including NovAtel Connect from www.novatel.com/support/info/documents/809.
To maximize the application of the receiver’s capabilities, become familiar with the commands
and logs described in the OEM7 Commands and Logs Reference Manual (OM-20000169).
3.1.1 Serial Ports
The receiver can communicate with a computer or terminal via a serial port. For communication
to occur, both the receiver and the operator interface have to be configured properly. The
receiver’s default port settings are as follows:
l
9600 bps
l
no parity
l
8 data bits
l
1 stop bit
l
no handshaking
l
echo off
l
break on
The data transfer rate determines how fast information is transmitted. Take for example a log
whose message byte count is 96. The default port settings allows 10 bits/byte (8 data bits + 1
stop bit + 1 framing bit). It therefore takes 960 bits per message. To get 10 messages per
second then requires 9600 bps. Also remember that even if you set the bps to 9600, the actual
data transfer rate may be lower and depends on the number of satellites being tracked, data fil-
ters in use, and idle time. It is therefore suggested that you leave yourself a margin when choos-
ing a data rate.
The minimum suggested baud rate for most applications is at least 115200 bps for GNSS
only or 230400 bps for GNSS+INS. If the buffer overrun flag is present in the
RXSTATUS log (refer to the OEM7 Commands and Logs Reference Manual (OM-
20000169)), log at a higher baud rate if possible, or change to a medium supporting
higher bandwidth (USB or Ethernet).
Although the receiver can operate at data transfer rates as low as 300 bps, this is not
recommended. For example, if several data logs are active (that is, a significant amount
of information needs to be transmitted every second) but the bit rate is set too low, data