User Manual

USER MANUAL
3-11
2. CONFIGURATION
2.1 Introduction
The RS-232 serial communications interface to the OEM-900 is intended to provide the means of communication
with the radio. Data may be passed through this interface normally or the radio may be configured using a
specialized subset of the industry standard modem AT command set.
2.2 Data Transfers
Data may be sent to or read from the radio link by using this communications interface as one would a regular RS-
232 serial port. A write to the port will cause the data to be sent through the radio link, whereas the arrival of any
data from the radio link will automatically be sent to the host via this port. By default, the radio will power up into
the data transfer mode of operation.
2.3 Commands
The host may modify the configuration of the radio by issuing commands via this communications interface using a
specialized subset of the industry standard modem AT commands.
To enable the radio to respond to these commands, it must first be switched from data to configuration mode. This is
achieved by observing two seconds of silence on the transmitter line, followed by sending the ASCII escape code
sequence: ‘+++’ and then followed by an additional two seconds of silence. Upon completion, the radio will then
accept a stream of configuration data.
Configuration information is sent to the radio in the form of one or more command strings. Each string is sent to the
port prefixed with the ASCII ‘AT’ attention code. The radio will acknowledge each command string received with
the ASCII ‘OK’ string. Those commands requiring the radio to return configuration information to the host will first
be answered with the data followed by the acknowledgement string.
EXAMPLE: Following power up, the host places the radio into configuration mode
Host: <2 seconds silence> +++ <2 seconds silence>
Radio: OK<CR><LF>
EXAMPLE: The host sets the radio’s ID code.
Host: ATS1=25<CR><LF>
Radio: OK<CR><LF>
EXAMPLE: The host reads back the radio’s ID code.
Host: ATS1?<CR><LF>
Radio: 25<CR><LF>OK<CR><LF>
EXAMPLE: After the configuration procedure has been completed, the radio is returned to the data mode.
Host: ATD<CR><LF>
Radio: no response (enters data mode immediately)
The complete command set for the radio is defined in Table 2.3-1.