WMA-5 Operation Manual V. 1.01
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Digital Communication Protocols and Software
Once a connection is made to the WMA-5 as described in the previous section, communication software
is needed to read, display and record data. This section describes three software programs and
protocols for utilizing WMA-5 data: WMA-5 Command Set for direct communication using WMA-5 ASCII
character strings, GAS Software for a Windows based graphical user interface with graphing and logging,
and Web Pages which are available only with the WiFi Option.
WMA-5 Command Set
When a computer is connected to the WMA-5 using either the USB cable or the RS232 port, a
communication protocol and command set comprised of ASCII characters and strings allows receipt of
WMA-5 data and setting of WMA-5 parameters. A terminal emulation program (
i.e.
Hyperterminal,
TeraTerm or PuTTY) is generally used for this, but other custom user software can be made to observe
and interact with the WMA-5 through these commands also.
Measured data is continuously output by the WMA-5 through the currently active port (USB or RS232).
The time interval can be modified using the Host Measure Interval setting (default is every 1 second). The
data format is dependent on the Host Measure Format setting selected. See Host Measure Settings
section to modify these parameters.
Sending a command
To initiate a command, the Host (
i.e.
Hyperterminal) sends an ASCII string in CSV format to the WMA-5.
The command can be sent with or without a CRC-8. If a CRC-8 is sent, a ‘C’ follows the CRC-8 value.
For example,
Host sends command without CRC-8: S,1,25<CR>
Host sends command with CRC-8: S,1,25,080C<CR>
The CRC calculation includes everything but the CRC itself and the ‘C’ character. In the example above,
the CRC was calculated from the string “S,1,25,”.
The command sent is processed by the WMA-5 after the command string terminator <CR> is received.
The command is successful if the string is under 90 characters. If a CRC-8 is present, the CRC-8 also
needs to be correct for the string to be successful.
On successfully receiving the command string, WMA-5 sends an acknowledgement by sending to the
Host a ‘+’ followed by a <CR>.
On a failure, a ‘-‘ is sent back to the Host with a <CR>.
A failure can be caused by a string longer than 90 characters or an incorrect CRC.
Receiving a response
Depending on the value of the CRC parameter (See Get/Set Parameter Values Table below), a CRC
will/will not be appended to the command received from the WMA-5. If the CRC parameter value is ‘0’
(CRC Off), no CRCs will be appended to any of the commands received from the WMA-5. If the CRC
parameter value is ‘1’ (CRC On), CRCs will be appended (including the ‘C’) to all commands received
from the WMA-5. See Get/Set Parameter Values Table for more details on turning off/on the CRC.