Campbell Scientific SC115 CS I/O 2G Flash Memory Drive with USB Interface - Manual (Page 23)

SC115 CS I/O 2G Flash Memory Drive with USB Interface
11. Serial Communications Interface Function
The SC115, when used as a serial interface, uses the Campbell Scientific SDC
protocol to facilitate communications between the datalogger and a PC. The
SDC address can be set to 7, 8, 10, or 11 (See Section 7.1, SC115 Settings).
Consider the following points when using the SC115 as a communications
interface:
• Use the provided extension cables to establish the physical connections
between datalogger, SC115, and PC BEFORE opening LoggerNet.
• When selecting a port in the LoggerNet Network Map for USB to CS I/O
communication, the COM port SC115 (COM#) must be selected. SC115
MSD (COM#) may also appear as a choice, but must not be selected as it
does not support the communications interface mode.
• Always click Disconnect within the datalogger support software Connect
window prior to breaking the physical connection between the PC, SC115
and datalogger. If this rule is not observed, and communication problems
develop, follow the procedure in Section 13.1, Breaking the Physical
Comms Link.
• Do not connect two SC115s to a PC at the same time if both are attached
to powered dataloggers. This can cause confusion of virtual com ports on
the PC (as memory devices, two SC115s may be attached to a PC at the
same time).
12. Troubleshooting Memory Drive
12.1 Preventing Data Corruption
To avoid corruption of SC115 memory, never remove the SC115 from the
datalogger during data transfer. The flashing LED indicates when data are
being written to the SC115. Should the SC115 be removed while the LED is
flashing, the most likely result is that the current data file will be corrupted. In
addition, a FAT sector or the directory link sector may become corrupted. This
condition requires that the SC115 memory be reformatted, which will result in
the loss of all data.
When either the NumRecs/TimeIntoInterval or Interval parameters are set to a
non-zero positive value (resident modes), there is a risk that the datalogger will
begin writing data to the SC115 at the exact moment it is being removed from
the datalogger, resulting in data corruption. To prevent this, set these
parameters to values that allow the time between writing data to be easily
discerned (such as an interval of 10 seconds) by watching the LED. The user
then times the removal of the SC115 to occur when the datalogger is not
writing data. See Section 10.5.2, Resident Interval Mode Example.
Another method is to set the NumRecs parameter in TableFile() to match the
Size parameter in the associated DataTable() instruction. Depending on the
rate at which records are written, this can cause data to be written to the SC115
at long intervals, greatly reducing the chance of removing the SC115 from the
datalogger while transferring data. See Section 10.5.3, Resident Record
Number Mode Examples (second example).
If SC115 data becomes corrupted, first attempt to retrieve all files from the
SC115. Reformat the SC115 per Section 14.2, Formatting Memory.
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