Motor Control; Exposure & Gain Control - Motorola Symbol SE4400 Integration Manual

SE4400 Integration Guide

Motor Control

The SE4400's lens system can be dynamically set to near or far focus positions:
• The near focus allows the SE4400 to focus on objects that are about five inches
away.
• The far focus allows the SE4400 to focus on objects that are about nine inches
away. This improves distance picture taking capability.
• Toggle mode uses the superset of the two focus positions, allowing the SE4400 to
achieve excellent working range across a variety of bar code densities.
Table 5-4 describes the focus position control.
FOCUS_CTRL1 FOCUS_CTRL2
0 0
0 1
1 0
1 1
Once instructed, the motor moves and settles within 20 ms, meaning that for each frame in
which the focus was changed the exposure time cannot exceed a frame time minus 20 ms.
If a focus position is forced to near or far, the exposure time can be as large as a frame time
as long as the motor is given 20 ms to settle from the time the focus position is forced to
the time the first image exposure begins. Even if toggle mode is not used, any change to
the focus position should occur at the beginning of the frame to allow the motor to settle
before the next exposure.
Exposure & Gain Control
In Mode 3, the exposure time is the period that EXSFT is held low. In Mode 1, the exposure
time is set in line times to I
results in an exposure time of 157 x 764T = 10 ms. Once set, the exposure value occurs
during the next frame, which is read out during the frame after that. The SE4400 starts in
5-16
Table 5-4. Focus Control Definitions
Operation
Motor completely OFF
Far Focus Position Selected
Near Focus Position Selected Motor forced into near position.
Toggle Mode
2
C register 151d. For example, in
Comments
Motor not held in either
position.
Motor forced into far position.
Motor toggles between near
and far positions on each rising
edge of EXSFT.
Figure 5-5, a value of 157