Campbell Scientific PC208 Datalogger Support Software - Manual (Page 85)

SECTION 5. TELCOM
5-11
station file with the 3 digit ID as its name and
interrogates the datalogger as specified in the
"Data Collection Method".
TELCOM can also answer calls from other
computers or terminals. The caller should send
carriage returns on an interval of approximately
0.25 seconds. TELCOM uses the carriage
returns to determine the baud rate (valid baud
rates are 300, 1200, 2400, and 9600). Once
the baud rate is set, TELCOM will execute
RING.BAT, a batch file which must be created
to set up the desired communication with the
remote caller. Refer to RING.BAT later on in
this section.
Once the modem is allowed to answer the
phone the Ring Indicator becomes inactive.
The Carrier Detect (CD) line from the modem
must then become active within 60 seconds or
the PC201/PC203 will power down the PC.
Once the PC201 sees the CD go active, the
watchdog timer will stop counting down. When
the CD becomes inactive, the timer will resume
counting down. The PC power will be left on
until the timer reaches zero, which should be
within 60 seconds of when the CD becomes
inactive. With no PC201, TELCOM will wait 30
seconds for the CD to go active and will return
to the wait state within 30 seconds of when the
CD becomes inactive.
STATION FILE NAMES FOR CALLS FROM
DATALOGGERS
If dataloggers are going to initiate
telecommunications, station files must exist with
the three digit ID as the station name. These
might be separate station files from those used
for the TELCOM initiated calls, or the station
names used in the script file could be the same
three digit IDs.
When PC initiated calls are the primary means
of retrieving data and datalogger initiated calls
are used to report alarm conditions, a different
station name for PC initiated
telecommunications allows one to use letters for
the name, which may have more meaning to a
human looking at the files. A separate data file
(i.e., "123.DAT") is kept for datalogger initiated
calls. The station file for the datalogger initiated
call can specify a different data collection
method than that used for PC initiated calls.
For example, the data logged since the last call
could be retrieved in PC initiated
telecommunications, maintaining a record of all
data, and the datalogger calls could save only
the 5 most recent arrays. After TELCOM has
collected the data from the .STN file it will look
for a file with the same 3 digit ID with a .BAT
extension. If it exists it will execute the batch
file before it goes back to the wait mode or
powers down.
If datalogger initiated calls are used as the sole
means of retrieving data, create only one station
file for each station and give it the 3 digit ID for
its name.
RING.BAT FOR COMMUNICATION WITH
ANOTHER COMPUTER
RING.BAT contains any commands necessary
to set up the PC for communication with a
remote terminal. The RING.BAT file can be
created using the PC-DOS Line Editor (EDLIN),
COPY CON:, or some other editor program.
Several commercially available
telecommunications software packages (and
public domain software) allow a user to set up a
remote computer to be accessed by a calling
computer. For example, with computers
running KERMIT (public domain software) the
RING.BAT file would contain "Kermit set port 1,
set baud 1200, server". This would allow the
calling computer, also running KERMIT, to send
and/or receive files. In most cases, the calling
and remote computer need to have the same
communication software installed. If the
communication software used ever drops the
DTR line it may be necessary to set switch 1 on
the Hayes Modem (Table A-1) in the down
position to prevent the modem from hanging up.
The RING.BAT can also contain DOS
commands to redirect the input and output to
the serial port. For example, the batch file:
CTTY COM1
COMMAND
redirects keyboard input and screen output to
COM1. This allows a remote terminal,
communicating via a modem to COM1, to
function as the terminal of the computer. The
command "CTTY COM1" redirects I/O to
COM1. The command "COMMAND" loads
another "shell" of DOS. When the user is
finished with the computer, typing 'EXIT' causes
the computer to pop out one "shell" completing
COMMAND and the batch file. TELCOM again