Honeywell IS4911 Manuale Utente

 

 

16 

The Video Mode allows for streaming video from the CMOS imager.  The main advantage in the mode is that 
the user has fine control over the exposure time.  Fine control over the exposure time makes this mode well 
suitable for high ambient light applications.  The Video Mode is initiated through commands via the I

2

C bus.  

During this mode of operation, the Trigger signal must be held low.  If lighting is required, the Illumination LEDs 
can be controlled via the Illum_On control signal.  

Control of all signals and image dataflow in Video Mode is done in software by the engine device driver and 
CamLib APIs included in the Software Development Kit.  See SDK documentation for more details. 

When not in Video Mode, the image sensor is always ready for Snapshot image acquisition. 

The engine uses a targeting LED to indicate the center of the imaging field.  This LED can be activated at any 
time by asserting the Aimer signal.  The targeting LED is independent of the mode of operation and 
illumination.  However, it is strongly recommended that the targeting LED not be activated during image 
acquisition as the light from the targeting LED will be visible in the image and may result in “hot 
spots”.  Control of the aiming mechanism is done in software by the IS4910 device driver and CamLib APIs 
included in the SDK. 

The IS4910 series engines use an I

2

C compliant interface to communicate with the host system.  The bus 

allows the host to communicate directly with the image sensor and illumination microcontroller.  Both of these 
devices function as auxiliary* devices on the bus.  The illumination Microcontroller is capable of running at 
speeds up to 100 kHz whereas the image sensor can support frequencies up to 400 kHz.  The standard 
configuration of the IS4900 series of imaging engines does not incorporate pull up resistors on the SDA and 
SCL lines in order to allow flexibility for the end user when choosing the resistor values.  These resistors must 
be provided by the host system and sized to meet the I

2

C timing requirements.  Timing provided by the I

2

C bus 

specification must be observed in order to guarantee proper operation of the engine.  

The two I

2

C devices used in the IS4910 Engine use the following addresses: 

•  CMOS Image:  0x10 

•  Illumination Micro:  0x61 and 0x70 

For details regarding programming of the image sensor, please refer to documentation provided with the 
Software Development Kit.  For details regarding the I

2

C protocol, see the Phillips I

2

C specification. 

 

* In the Phillips I

2

C specification, auxiliary is defined as slave.