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Appendix G Data Transfer Protocol
(Version 2.0)
Activate Data Transfer
•
In normal state, the PC weather station is inactive and does not react to V24
signals.
•
To activate it, set the RTS line < -9 V and the DTR line to > 9 V.
•
The PC weather station activates its interface following a High-Low side of a
pulse on the DTR line.
•
After the PC weather station has started and stabilized its main oscillator
(approx. 30 ms), it transfers a "ETX" character to confirm that it is ready to
receive.
•
Data transfer can then begin.
•
The PC weather station is reactivated as soon as the DTR line is reset to
'High' or if no valid start command (SOH) is received for 0.5 s.
•
Data exchange via the V24 has priority over receipt from a sensor. Therefore,
the receipt of data should occur at greater intervals.
•
Datasets are, therefore, only deleted from the PC following an explicit re-
quest. By comparing the block numbers transferred in the data set, the PC
can determine whether the next dataset has actually been selected.
•
Each value stored is assigned a flag which indicates whether the value is new
or represents the previous value received.
•
The PC weather station can either receive either 8 temperature/humidity sen-
sors + 1 indoor sensor with pressure or 15 temperature/humidity sensors + 1
indoor sensor with pressure.
After changing the operating mode, all the stored datasets are deleted from
the radio interface and all the sensors re-identified. During this period of ap-
prox. 6 minutes there must be no communication with the interface.
60
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