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9.3 Serial Port Command and Control
The Bravo MRI II serial port sends and receives strings of ASCII characters. These
strings usually contain several pieces of information. Each piece of information has a letter
prefix to identify the information that immediately follows. This information is usually a
number in ASCII format. Decimal points are not sent, the decimal position is inferred by the
prefix letter. The end of a piece of information (such as a number) is denoted by the prefix
letter of the next piece of information. At the end of the command (or response) string, an
End Of String (EOS) marker is appended. This EOS marker pushes the last piece of
information through the software routines. Some commands do not require the EOS marker.
The Bravo MRI II unit sends an EOS marker in response to a command. If the Bravo MRI II
doesn’t understand the command, no EOS response occurs. The ASCII char ‘*’ (ASCII 0x2a)
is used as the EOS marker. The Bravo MRI II unit appends the EOS character to the end of
any response.
The commands to the Bravo MRI II unit fall into two major categories;
1. Data request
2. Unit setup
These commands and the unit’s responses can be controlled or read via the Director
software or by any terminal program running on a PC. The controller unit that communicates
with the Bravo MRI II unit will be referred to as the Terminal throughout this document.
9.3.1 Data Requests
The data requests are short commands that receive a fairly large block of data from the unit. This
data can be one of several formats, as selected in the unit setup. These formats are:
Impedance magnitude and angle.
Resistance and reactance
SWR and return loss
Reflection coefficient magnitude and angle
For fastest throughput, set the unit into R-X mode (D101) and perform calculations to other
formats in the Terminal software.
The contents of save memory locations can be loaded into the terminal. All save memory
locations contain the instrument settings of the Bravo MRI II unit, while only some of the locations
contain saved data.
Also the entire unit setup data can be extracted in a fixed format block.
9.3.1.1 Data Request Commands
9.3.1.1.1 R
Send a block of measured data (data dump). The response is dependent upon the type
of data being sent out of the unit. The type of data may be set by one of the setup
commands (S100) or is determined by the left plot on the unit. This command requires no
EOS marker, but one may be sent if desired.
9.3.1.1.2 Q
Send the Q calculation result. The number send must be divided by 10 to get the correct
result. This command only operates in the SWR mode. . No EOS marker is required if, but
one may be sent if desired.