Metrologic IS4910 Series, Руководство программиста

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IS4910 D
EVICE
D
RIVER
Power Management
The driver supports the standard power management interface PMCLASS_GENERIC_DEVICE used by
the Power Manager under Windows CE to query the power capabilities of the device and to control its
state. The supported power states are as follows:
• D0 – device is fully powered
•
D2 – device is in low power state
•
D3 – device is in standby state
•
D4 – device is in power down state
An application can control or query the power state of the device by using the WinAPI functions
SetDevicePower(), GetDevicePower(), SetPowerRequirement(), and ReleasePowerRequirement().
In order to take pictures or to start, pause or stop the video mode, the camera must be in full power state
(D0).
In order to change camera’s properties, the camera must be in full power state (D0) or in low power state
(D2).
When turned to standby state (D3), the camera is not operational, but the power should still be applied to
it. While the camera is in this power state, other devices in the host system can still use
I
2
C bus.
The camera must be turned to power down state (D4) if and before the host system completely unplugs
the power from it. The failure to turn the IS4910 camera to power down state (D4) prior to unplugging the
power from it may result in rendering the camera inoperative and may require reinstallation of the IS4910
software. While the camera is in this power state, other devices in the host system may or may not use
I
2
C bus. It depends on the value of I2C_PowerOff setting in the IS4910 Driver initialization file
VuQuest2D.ini. If the I2C_PowerOff setting is 1, then the IS4910 device driver disables I
2
C controller and
drives I
2
C lines low as required by the IS4910 specification (see IS4910 Series Area Imaging Engine
Integration Guide for details), making I
2
C bus unusable for other devices. If the I2C_PowerOff setting is
0, then the driver does not change the status of I
2
C controller, making I
2
C bus available for other devices
in the host system. In the latter case, however, the host system is responsible for setting the IS4910’s I
2
C
lines to proper states in accordance with the requirements of the IS4910 hardware. The default value of
I2C_PowerOff setting is 0. In order to wake up the camera from the D4 power state, the host system
must apply the power to it prior to requesting the change of its power state from D4 to any other
supported power state.