Serial Port Communications
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:
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9600 bps
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no parity
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8 data bits
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1 stop bit
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no handshaking
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echo off
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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 filters in use, and idle time. It is therefore suggested that you leave yourself a margin when choosing a data rate.
The minimum suggested baud rate for most applications is 115200 bps
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 overflows the serial port buffers, causing an error condition in the receiver status that results in lost data.
Refer to Serial Ports for additional default setting details.
The following ports are supported and can be configured using the commands listed.
Change the COM Port Settings
To change the settings on a COM port, use the SERIALCONFIG command. For example:
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To change the data rate of COM2 to 115200, enter:
SERIALCONFIG COM2 115200
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To change the data rate of COM1 to 57600 and enable even parity, enter:
SERIALCONFIG COM1 57600 E
Configure a COM Port to Use RS-232 or RS-422
COM1 of the OEM729 and COM1 and COM2 of the PwrPak7 communicate using RS-232 protocol by default, but can be configured to use RS-422 protocol.
The SERIALPROTOCOL command is used to select RS-232 or RS-422 for the COM port.
Commands are executed after the receiver has completed booting so the communication lines may be configured incorrectly during the time taken to boot and before the command can be processed. For automatic configuration, the SERIALPROTOCOL command can be saved using the SAVECONFIG command.
After switching a COM port from RS-232 to RS-422, send a carriage return (CR) on the newly configured port to flush the buffer prior to sending new commands on the port.
Communicating using a Remote Terminal
One method of communicating with the receiver is through a remote terminal. To communicate with the terminal, the receiver requires only the RX, TX and GND lines be used.
COM ports on OEM7 receivers cards use LVCMOS voltage levels and require an interface circuit to communicate with a remote terminal. The exception is COM1 on the OEM729 that uses RS-232 voltage levels and can interface directly to a remote terminal.
Communicating using a Computer
A computer can emulate a remote terminal as well as provide the added flexibility of supporting multiple command batch files and data logging storage files. Use any standard communications software package that emulates a terminal to establish bidirectional communications with the receiver. Examples include NovAtel Application Suite and PuTTY. All data is sent as raw 8-bit binary or ASCII characters.
Refer to Communicating with the Receiver for details.
COM ports on OEM7 receivers cards use LVCMOS voltage levels and require an interface circuit to communicate with a computer. The exception is COM1 on the OEM729 that uses RS-232 voltage levels and can interface directly to a computer.