Serial Data Format

RCP8 is controlled by a two–way, asynchronous RS-232 data line that is typically run at speed of 19.2 K baud.

A host computer controls the servo and the antenna while receiving feedback status.

Information is transferred in packets of 2 or more bytes. Each packet begins with a SYNC byte and ends with an END byte of FF(Hex). All SYNC bytes have the MSB set and the value indicates the type of packet to follow. The available packets are 80(hex) for antenna, C0(hex) for BITE, and B0(hex) for time. Each packet–type has a specific direction of travel, such as to or from RCP8. Packets can arrive in any order in the serial stream.

The time stamp is a 14-bit counter incremented by RCP8 once per millisecond. RCP8 should latch all the data for a packet at the same time. This counter allows the host computer to accurately judge the time between samples without the serial line latencies and fluctuations due to the time sharing operating system.

Supported Serial Data Formats
Format Purpose

RCV01

XMT01

 For older systems

RCV02

XMT02

 For newer systems.
RCV03

For systems on moving platforms, such as ships or airplanes.

These correct the radar's measured radial velocity for the motion of the platform. To make this correction, the three–dimensional velocity and orientation of the platform must be recorded. Typically, the information comes from an inertial navigation system (INU).

For shipboard systems, an update rate of approximately 20 reports per second can satisfy the velocity correction requirements at 19 200 baud.
Angle Values in Serial Data Formats
Angle Value Description Transmit Value
Angular speed

In the XMT01 format, the angular speed is a signed number in units of 0.55º/s.

In other formats, the angular rates are in signed 14–bit binary angles per second. The largest possible value is 180º/s (30 rpm) and the step is 0.022º/s. All velocities are in signed cm/sec with the altitude in signed meters. If some of the information is unavailable at the full resolution of the data format, the low bits are filled with zeros.

 N/A
Azimuth and elevation

The azimuth and the elevation angles are corrected angles relative to the north and are the angles that the antenna is pointed relative to the deck of the platform. These calculations are derivable from the other angles but are also reported to assist in data analysis, especially if one of the sensors or the stabilization fails.

 14–bit binary angles
Heading

The direction the platform is pointed. This is not the same as direction of motion.

The platform could be pointed one way and drifting backwards.

 14–bit binary angles
Latitude and longitude

The position of the platform is reported by the latitude, the longitude, and the altitude.

On ships, since the altitude may not be implemented for systems on ships, the setting is 0.

 21-bit binary angles
Pitch

The pitch is the angle between the fore–and–aft axis of the platform and the horizontal is measured in the vertical plane. The pitch is positive when the bow is down.

The pitch is measured in the plane perpendicular to the fore–and–aft axis, which is generally not the vertical plane, and

note The pitch can be directly measured by a level on the fore-and-aft axis but the roll cannot be directly measured by a one–axis tilt meter.
 14–bit binary angles
Roll The roll is the rotation angle about the fore-and-aft axis in its pitched position. The roll is positive when the deck is down on the port side. 14–bit binary angles