Campbell Scientific RF310, RF312, RF313 Narrowband Radios - Manual (Page 28)

Section 3. Radiotelemetry Network Components
3-6
The first step in setting up an RF link, once in the Local Command Mode, is to
create a setup block using the "S" command. The setup string is entered via the
computer as follows:
Sxxx yyy
where:
xxx = ID number of the RF310M which is acting as the repeater in the
link. If no repeater is used then xxx is omitted.
yyy = ID number of the EOL modem.
xxx and yyy are numbers from 1 to 255, inclusive. The user can have up to 12
repeaters in any RF link. Example 3-1 shows the setup block for an RF link
which will communicate through three repeaters to an EOL modem, with
Station ID numbers of 10, 25, 50, and 30, respectively. The Fast Command is
used to speed data transfer.
EXAMPLE 3-1. A Sample Setup Block
S10 25 50 30F
Notice that it is not necessary to include the station ID of the SOL modem.
Press [ENTER] following the setup string of station IDs to transmit the setup
block. When the RF link is established, a verification block is sent from the
EOL modem to the SOL modem. Upon receiving this verification block, the
SOL modem and EOL modem have entered the Transparent Mode of
operation. At this point, the dollar sign prompt "$" will be returned to the
computer screen. The datalogger connected to the EOL modem is now in the
Telecommunications Mode and will respond to the standard datalogger
telecommunications commands. If the verification block does not return
shortly, pressing [ENTER] will cause the SOL modem to return to the Local
Command Mode.
3.1.7.2 Maintaining the RF Link
Data can be transferred once the RF link is established. Data blocks are created
and transmitted by the SOL and EOL modems according to the following two
rules. First, characters received on the Serial I/O port are placed into data
blocks of 238 characters each. The block is then closed and transmitted. Any
remaining or new characters received at this point are placed into a new data
block. Second, if during this loading process a delay of 290 ms occurs between
characters, the data block will be closed and transmitted.
Most of the time, the SOL modem will be sending command strings which will
be answered by the EOL modem and the datalogger. The response from the
datalogger is not instantaneous. If a command is sent before the response from
the previous command has been received, the current command will be sent and
a possible collision of the RF signal may occur. This results in a loss of the
response and the current command. The general rule is that the person sending
characters should wait for the response to come back before issuing further
commands.