Controller data packet
Sample controller data packet
The ecoding of data from this sample packet is described below.
First two characters: ignorable flags
27100EF14892E44
Data is not represented in these two characters.
3rd through 7th characters : elapsed time since midnight
27100EF14892E44
This string of five characters is the hexidecimal represenation
of the number of seconds elapsed since midnight, as referenced to the
controller's clock. Controller clocks are generally incorrect and drift
over time.
Characters from the 8th position on, not including the final 2 characters:
loop events
27100EF(148)(92E)(...)44
Each block of three characters, starting from the 8th position
and continuing through all but the final two characters of Field 6,
are encoded loop transitions. Each three-character hexidecimal substring,
when converted to its equivalent twelve bits in base 2, describes a
single loop transition. The first six bits count the number of 1/60
second intervals ("ticks") that have elapsed at the time of
the loop transition. The seventh bit indicates the transition type ("on"
or "off"). The final five bits indicate the controller port
from which the transition was observed; the port corresponds to a particular
loop at that station, as indexed in the Controller
configuration files.
Final two characters: checksum
27100EF14892E44
The last two characters in each string are a checksum for
data validation. If the result of checksum applied to the rest
of the string does not match these last two characters, then the entire
controller data string is considered to be corrupt or incomplete.
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