Eurotech ZyWAN, Руководство пользователя

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ZyWAN - User Manual
92 110150-1001F
FIELD/OPTION EXPLANATION
Enable Cache? Select Yes to enable caching of GPS data. When caching is
enabled, the ZyWAN stores 100 positions in non-volatile
memory. After this cache is filled, the oldest positions are
discarded. Once the network connection is re-established,
positions in the cache will transmitt in a first-in, first-out order.
This is the only option for ActSoft mode, and the option is not
available to set to No.
When Enable Cache is set to Yes, a UDP acknowledgement is
required from the host computer, which allows the ZyWAN to
verify the data has been received. If the UDP acknowledgement
is not received, the data points begin to be cached.
The Enable Cache option requires that the ZyWAN
network address must be accessible to the host
computer, since the host must initiate a one-way UDP
acknowledgement message to the ZyWAN. If the
acknowledgement is not received (due to network
problems, etc.), the ZyWAN caches the GPS points
based on the Request Interval and Send Threshold
parameters (above) and continues trying to send the
next point every 10 seconds.
When Enable Cache is set to No (Arcom format only), a UDP
acknowledgement is not required. The ZyWAN simply sends
out the GPS points when it can and does not store them locally.
If the host computer does not receive the position message,
those positions are lost.
Arcom Format for GPS Messages (UDP)
When using the Arcom Format for GPS data, the position message is transmitted using the User Datagram
Protocol (UDP). If caching is enabled, the ZyWAN waits a minimum of 10 seconds to receive an
acknowledgement message after transmission of a position message. If a response message is received
that does not contain the characters ACK or no message is received within the timeout period, the position
message is retransmitted. This process continues indefinitely. The ACK must be 3 ASCII characters (0x41
0x43 0x4B).
The position message is defined next. The first 12 bytes are a header, followed by 19-byte portions
containing the timestamp and position information. The number of these 19-byte portions is determined by
the Send Threshold parameter. All data is in binary big-endian format, unless otherwise specified.
Message header:
som(1) snum(10) npos(1)
Position data (repeated):
sval(1) time(4) stat(1) sats(1) lat(4) lon(4) psrc(1) speed(1) head(2)