Wireless Mini Analyser User Manual
Wireless Mini Analyser User Manual V1_06
1_04
18 of 32
RD096 071112
6.2
Data Transfer
Transfer of the data collected by the Wireless Mini Analyser is achieved via the wireless serial link provided by the
Wireless PC Module and Wireless Analyser Module. The wireless modules provide a transparent 19200-baud serial
link between the host PC and the Mini Analyser. When operating with the Wireless Modules the serial port should
be configured as follows:
Data Rate
:
19200 baud
Data bits
:
8
Parity
:
No
Stop bits
:
1
Flow control
:
None
6.2.1 Command Transmission
Due to the single RF channel link between the host PC and the Wireless Mini Analyser, full-duplex serial
communication is not possible. The terminal interface within the Wireless Mini Analyser has been modified to
suppress the remote echo that is present in the standard firmware. As a result there is no requirement for the
terminal emulator, or other software, to wait for an echo character from the Wireless Mini Analyser.
If the Wireless Mini Analyser is used with a standard terminal program the entered characters will not be visible to
the user unless the terminal program is configured to provide a local echo. If remote echo suppression strategy is
not implemented then command transfers may fail due to clashes between transmitted and echoed characters on
the RF link.
6.2.2
‘last’ Command
The current contents of the set buffer may be
requested from the Mini Analyser at any time by use of the ‘last’
terminal command. In response to this command the Wireless Mini Analyser will transmit a fixed length data block
containing the collected data. As the Wireless Mini Analyser is generally intended for connection to a terminal
program, the data is transferred as ASCII characters.
The transferred data consists of 124 characters of header (2 lines of 62 characters), followed by 244 characters of
data (4 lines of 61 characters), regardless of sensor generation (G2 or G3). Appended to the collected data is a 7-
character line containing a checksum that is used to verify data integrity.
Pos Chan SerialNo Pact Tact RSSI RBL Mode RLRot TimeStamp
(62 chars)
---------------------------------------------------------------------------------------------
(62 chars)
0: -- 1402246943 1000 23 54 236 0x41 0x00 1360360
(61 chars)
1: -- 1402246937 1025 24 54 236 0x41 0x00 1538230
(61 chars)
2: -- 0 10000 -40 0 0 0x00 0x00 0
(61 chars)
3: -- 0 10000 -40 0 0 0x00 0x00 0
(61 chars)
0xf372
(7 chars)
The CRC is generated by the CCITT algorithm G(x) = x
16
+ x
12
+ x
5
+ 1 with a 0x0000 register preload value. The
CRC is calculated over the 244 characters of the data payload.
On receipt of the data block at the host PC the data should be validated by means of the CRC. If the CRC validates
correc
tly, then the host PC should complete the data transfer by sending an ‘ack’ packet back to the Wireless Mini
Analyser. An ‘ack’ packet consists of the characters ‘ack’ followed by a linefeed. If the CRC fails to validate, then the
data may be re-requeste
d via the ‘last’ command.
The complete sequence for the ‘last’ command is shown as follows:
At the USER1> prompt, the host PC sends the ‘last’ command
On receipt of the ‘last’ command the Wireless Mini Analyser responds with the data and CRC block, followed by a
USER1> prompt
The data block received by the PC is validated by a CRC check
If the check is successful the PC responds with an ‘ack’ message at the USER1> prompt
