STV-DCASLASHVGA-E01 datasheet(12/60 Pages) STMICROELECTRONICS

12 / 60 page

PRELIMINARY

Digital Camera Chipset; Customer Datasheet, Rev 3.0, March 2000

STV0680A + VV6444/6410/6500

CDSTV0680F-C

Commercial in confidence

STV0680F_contents.fm

2. Camera has been ‘gone to sleep’ i.e. moved into standby mode. Pictures are retained in memory.

3. Picture has been successfully taken after the user presses the capture button.

4. Picture has NOT been taken after the user presses the capture button. This indicates to the user that there is insufficient

light, or that the exposure control was not ready due to a rapid change of lighting in the scene.

5. Picture has NOT been taken after the user presses the capture button, due to picture counter having reached the maximum

number of images. The user has the chance to zero the counter if desired.

6. End of continuous capture in un-tethered ‘Continuous’ mode, due to memory full.

7. Self-timer activated and counting down.

2.3

Battery Level Detect and USB auto-switch

An on-chip battery level detector on STV0680A detects when the battery voltage falls below a threshold. This threshold is

determined by the designer, dependant on the perception of what remains as ‘acceptable’ image quality as the battery voltage

falls. The chosen threshold level is determined by a resistor value, as shown in Section 9. Where no USB has been detected, the

LCD display flashes, which indicates that the battery is low. Where a USB connection has been detected, the camera sources

power from USB, if certain additional hardware is fitted.

Note: It may be a requirement of certain USB compliance tests that such additional hardware is included in the camera design, in

order to enable the camera to switch to supply from USB and hence report back to the PC while connected to the USB bus

without a battery.

2.4

PC interface options and software support

Either USB Interface (full speed 12Mbit/sec max.) or RS232 interface (115.2Kbaud) is supported by the chipset, with driver

software available from ST for both. The interface type is auto-detected by the chipset. PC software can be one of the following

(exact compatibility is clarified in Table 3):

1. Simple image upload demonstration software supplied by ST, allowing uploading of stills or ‘continuous’ images. This soft-

ware should not be supplied as an end-user product.

2. TWAIN driver to suit all TWAIN compatible imaging applications

3. Video for Windows driver for tethered video mode (USB only)

4. Custom end-user software developed by OEM using SDK (for SDK availability, contact ST). The SDK is supplied by ST as a

32-bit DLL format, running on Windows 98, and accessed through a documented software interface. This provides the basis

for developing a custom software application for uploading stills and/or video. See Section 5. for further details.

2.4.1

USB

Complete images (displayed as either thumbnails or in full resolution), or the entire SDRAM contents (e.g. for uploading

continuously captured image sequences, recorded using ‘Continuous Capture’ mode) can be downloaded through USB, and

USB connection also allows for tethered video mode to be activated by the USB driver.

Thumbnail image download is extremely fast for the entire memory contents in the camera. Once a picture is selected for

download, full image download takes approximately 0.15 seconds per image for a CIF image (0.6 seconds for a VGA image),

plus post processing time per image.

For USB interface details, see Section 4.4.

Note: Actual USB download and post processing time also depends on PC performance and USB bus loading

2.4.2

RS232 (not available on STV0680-001)

Thumbnails of images, complete stored images, or the entire SDRAM contents can be downloaded through RS232, but tethered

video is not supported.

Once a picture is selected for download, full image download takes approximately 10 seconds per image for a CIF image (around

30 seconds for a VGA image), plus post processing time per image (of the order of 1 second approximately).

For RS232 interface details, see Section 4.5.

Note: Actual post processing time after RS232 download also depends on PC performance

2.5

Anti-flicker exposure and gain control

The chipset operates automatic exposure and gain control for either 50Hz or 60Hz mains-driven indoor lighting, using the same

12MHz crystal. This improves picture quality by selecting a set of exposure values which minimise ‘flicker’ effects. Detection of

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