DNF Controls ST300-CP - Manual (Page 5)

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Getting Started . . .
2. OVERVIEW
The ST300 will operate as an event driven device, transmitting information to the external device
when a change is detected.
In addition, the external device may poll the ST300-CP for status.
a. KEY PRESS DECODING
The ST300 will detect and decode changes in the Keyboard state. The ST300 will return
a 16-bit Scan Code that describes a key press or a key release. The Scan Code allows 2
key combinations to be detected and decoded.
b. WHEEL MODE
The External Device selects the current wheel mode:
0=
Off
1= Jog
2= Shuttle (with mechanical detents)
When OFF mode is selected, the wheel will not return position information and the
mechanical detents will be de-energized.
When JOG mode is selected, the mechanical detent will be de-energized. The WHEEL
POSITION will return a one-byte, signed value that represents pulses per time period.
Zero pulses in a time period represents that the wheel had no movement (stopped).
Positive value represents Clockwise movement. Negative value represents Counter-
clockwise movement.
When SHUTTLE mode is selected, the current wheel position will become the STILL
position of the wheel. The WHEEL POSITION will return a one-byte, signed value that
represents pulses (rotation) from STILL position. A positive value represents Clockwise
movement from STILL. A negative value represents Counter-clockwise movement from
STILL.
c. T-BAR POSITION
The T-BAR POSITION returns a one-byte value, that indicates the relative position of
the T-BAR from its STILL position.
The T-BAR assembly uses an incremental, not absolute encoder. At power up, the
ST300 prompts the user to move the T-BAR to its STILL position. Any time the T-BAR
is moved to its STILL position, the position value is zeroed, forcing a re-calibration.
d. KEY LEDs
The Key LEDs are controlled by the External Device. A three-byte (3) value sent to the
ST300 by the External Device determines the state of each LED, one bit per LED.
When bit = 1, the LED is on. When bit = 0, the LED is off.