Research Concepts RC2500 - Manual (Page 91)

84 RC2500 Antenna Controller Appendix E RC2500 Comm Protocol
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horizontal (if 'H' is specified) or vertical (if 'V' is specified) polarization specified for the satellite. If the field
contains a blank the polarization is not changed. For example, this command with 'H' in the polarization
field and 'SBS 6 ' in the sat_name/position field will specify an auto move to SBS 6 and the polarization
will be adjusted to horizontal for the SBS 6 satellite.
Form 2. If the sat_name/position field contains a valid pair of azimuth and elevation sensor position
counts the antenna will move to the position specified. The first 5 characters of the sat_name/position
field specify the azimuth position (azimuth sub-field) and the last five characters specify the elevation
position (elevation sub-field). Within each of the sub-fields the position must be right justified and left
padded with zeroes. For example, a sat_name/position field value of '0152500750' specifies an azimuth
position of 1525 counts and an elevation position of 750. For this form of the auto move command, only
the blank character is accepted in the polarization field. Note that the position must be specified in
position counts and not in an angle format. See the discussion below on the Mapping of Sensor Position
Counts to Displayed Angle.
Form 3. If the polarization field contains the 'P' character, the command is interpreted as a
go_to_polarization command. For this form of the command, the first 5 characters of the
sat_name/position field specify the target polarization position in the controller's internal polarization
position representation (polarization sub-field). The polarization position in the polarization sub-field must
be right justified and left padded with zeroes. The second 5 characters of the sat_name/position field
must contain '00000'. For example, if the sat_name/position field contains '0050000000' the polarization
control device is commanded to adjust the polarization to a position of 500. See the next paragraph for
more information on the relationship between sensor position and displayed angle.
Mapping of Sensor Position Counts to Displayed Angle
The RC2500 is designed to interface with antennas equipped with resolver type position sensors. The
resolver is excited by an AC voltage. The angle of the resolver shaft modulates the amplitude of a pair of
quadrature output signals. A resolver to digital converter (rdc) takes as its input the quadrature outputs of
the resolver as well as the excitation voltage and produces a binary output which is read by the RC2500’s
micro-controller The RC2500 is equipped with a 16 bit resolver to digital converter. A 16 bit rdc produces
65536 (or 2 16 ) unique binary output values, which are represented internally in the controller as numbers
in the range of 0 through 65535. It is these position counts which are passed to the controller in Form 2
and Form 3 of the Auto Move command. To convert from position counts to shaft angle use the following
formula ..
Resolver_Shaft_Angle = (Position_Count * 360.0) / 65536
Note that the resolver output wraps (or rolls over) from 360.0 to 0.0 degrees if the shaft is rotated 360
degrees. The resolver must be mechanically attached to the antenna so that this wrapping does not
occur within the antenna’s normal range of movement (to enable the controller to calculate which
direction to move to reach a target position). For this reason (and to facilitate calibration of the resolvers)
an offset angle is added to the calculated resolver angle. The sum of the resolver shaft angle and the
offset angle may be adjusted by adding or subtracting 360 degrees so that the resulting angle lies in a
desired range of values. It is this adjusted value which is displayed. Each axis has it’s own unique offset
angle. These angles are specified via the Azim Display Offset, Elev Display Offset, and Pol Display
Offset CONFIG mode items. The range of the ‘Display Offset CONFIG mode items are -179.99 to
180.00. Each axis will considered separately.
For the azimuth axis, the display angle will be the sum of the azimuth resolver shaft angle and the Azim
Display Offset CONFIG mode item adjusted by either adding or subtracting 360.0 degrees so that the
resulting angle lies in the range of 0.00 to 360.00 degrees.
For the elevation axis, the display angle will be the sum of the elevation resolver shaft angle and the Elev
Display Offset CONFIG mode item adjusted by either adding or subtracting 360.0 degrees so that the
resulting angle lies in the range of -99.99 to 260.00.
For the polarization axis, the display angle will be the sum of the polarization resolver shaft angle and the
Pol Display Offset CONFIG mode item adjusted by either adding or subtracting 360.0 degrees so that the
resulting angle lies in the range of -99.9 to 260.0.
Azimuth/Elevation/Polarization Jog Command
This command jogs the antenna in azimuth, elevation, or polarization. The command contains 11 bytes.
Here is the format of the command;