STV0681 Hardware Interfaces
STV0681
4.9
Flashgun hardware interface
STV0681 will revert to flashgun exposure when it detects GPIO2 is high. Ideally the hardware
should combine the two factors of (a) user intention (e.g. user switches on flashgun) and (b) charge
sensing (i.e. flash is charged up and ready to fire).
These two factors (a) and (b) are independent, since there may be a delay of several seconds
between switching on the flashgun charger, and the flashgun being able to fire. To revert to flashgun
exposure before the flashgun is completely charged up would cause very bad pictures to be taken
in low light conditions because there is no “low light” threshold when flashgun exposure is enabled,
since the camera expects a flash to fire. A suggested flashgun hardware interface is given in the
flashgun application note AN1312.
When flashgun exposure is enabled and the shutter button is pressed, a picture is taken and the
flash trigger pin GPIO7 is pulsed low at the correct point in time so that all lines of the CMOS imager
are exposed.
4.10 IR filter
An Infra-Red Blocking Filter is required to achieve correct colour response. The exact specification
for the IR filter characteristics are given in the reference design manual.
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ADCS 7283313C
STMICROELECTRONICS [ ST ]
