Appendix 7. Communication Protocol
This communication protocol is valid for USB or bre. The main difference
between the two is the port settings.
Ports
USB: it emulates a serial port service with CDC, automatically negotiated rate,
8 bits, no parity,1 bit stop. The Vendor ID and Product 0x1FC9 ID 0x807B of the
USB may be used to nd the port number opened by the driver.
Fibre: 230400 bps, 8 bits, no parity, 1 bit stop. The 0x0403 Vendor ID and
Product ID 0x6001 may be used to nd the number of communication port
opened by the FTDI driver.
Format of commands and responses
Communication is done through the exchange of strings with the XML format.
The SMP2 checks the frames received and rejects them if not well formed.
The XML format accepted by the SMP2 parser is as follows:
Command:
PC SMP2
General format of commands
<?xml version=”1.0” encoding=”ISO-8859-1”?>
<cmd>
<instruction>[String to identify the command]</instruction>
<params>
[Settings needed by the command]
</params>
<timeout_msec>[optional; max time to run the command]</timeout_msec>
<md5>
[MD5 of string from “<?xml” to the character previous to tag “<md5>”, in ASCII hex]
</md5>
</cmd>
User’s Manual Electromagnetic Field Meter SMP2 P. 83
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