User Guide
80
• set O.31 to “On” in one device and P.00 to “CELL” in
another one within the same RS485 network;
• put a PC monitor within the RS485 network.
Provided the above, any Hanna instrument with RS485 port
can be attached to the network and monitored remotely.
The modem must be configured (only once while setting up
the network) through a PC with an RS232 terminal program
(as HyperTerminal) or Hanna HI 92500 application soft-
ware (“Options” menu : “Configure modem”). That configu-
ration is performed automatically by HI 504 for the GSM
module. The string to be sent to the modem for configuring it
is: “AT&F0V1&D0&C0&S0X3E0&K0&Y0&W0<CR>”, (<CR>
= Carriage Return). In case the above command causes an
error in the modem answer, then it has to be divided into
smaller pieces: “AT&F0<CR>”, “ATV1<CR>”,
“AT&D0<CR>”, “AT&C0<CR>”, “AT&S0<CR>”,
“ATX3<CR>”, “ATE0<CR>”, “AT&K0<CR>”,
“AT&Y0<CR>”, “AT&W0<CR>”. This is needed because if
during processing of AT commands in the same line one of
them leads to an error, the following commands are not pro-
cessed. After slicing the configuration string into pieces, send
them all to the modem one by one till the end, even if one or
more of them give errors. The connection may be established
and work well even if some error occurs during configuration.
When making a call, after the data connection is established,
the “NNPWD...” command (where “NN” is the address of the
device controlling the modem, i.e. the one with O.31 set to
“On”) must be issued by the remote computer within 15 sec-
onds.
When the data connection is up, the RS485 protocol for a
remote connection is all the same as for a local network (see
the previous section). An automatic disconnection takes place
if no character is received in the RS485 network in 3-4 minutes.
When a modem connection is up, the cellular module does
not send any SMS. If an error for which the SMS sending is
enabled is active after closing the modem connection, an
alarm SMS will be sent by the HI 504 after disconnection.