the exact “yyyy-MM-dd HH:mm:ss” 24-hour format, occur on the first line, and end with a newline
character. Figure 12 provides an example time.txt file that will initialize the RTC to 2:26:30 pm June
16, 2014.
The time file method of setting the RTC does not require special communication drivers so it can be
implemented using a simple text editor. Direct initialization of the RTC is possible but requires
specific device drivers and software from Gulf Coast Data Concepts.
The RTC maintains ±50ppm accuracy (-40°C to +85°C), which means that the accuracy may drift
about 4 seconds every day. The RTC is powered by the battery at all times, even when the logger is
“off”.
Gulf Coast Data Concepts
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X16-1D, Rev B
Initializing the RTC ensures that the start time and individual time stamps can be
correlated to an absolute time – the year, month, day, hour, minute, second, and fractional
second. An uninitialized RTC or reset of the RTC will lead to indeterminate start time
recorded in the data file header.
After unplugging the logger from the USB port, the logger will load the config.txt file and
time.txt file, if present. Therefore, there is a delay between when the time.txt was created
and when the logger actually loads the time information. For most applications, this simple
method of initializing the clock results in sufficient accuracy.
Figure 12: Example Time Entry in time.txt File
Initialization of the RTC is limited to +/-1 second. The RTC register that handles the
fractional seconds counter is not accessible so the initialization process can not reset the
seconds to an even value.
