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IXUS175/ELPH180 Notes 
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CHDK is a hack, use at your own risk!

This is an ALPHA port. Some CHDK features are not implemented and
many have not been fully tested.

Porting thread https://chdk.setepontos.com/index.php?topic=13063.0

Original code from tsamma in https://chdk.setepontos.com/index.php?topic=13063.msg133207#msg133207
Additional code from blackhole in https://chdk.setepontos.com/index.php?topic=13063.msg133875#msg133875

General camera and CHDK port information
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Default alt button is PLAY. ERASE and VIDEO may also be used, but will
conflict with some CHDK shortcuts

Raw shortcut key is VIDEO

Has ND filter, does NOT have adjustable aperture

~3MB of RAM is available to CHDK

Neither VER.REQ nore VERS.REQ work to obtain the Canon firmware. Use
a tool such as ACID to obtain the correct firmware version

Runs with battery door open, no override required.

Analog AV detect and battery temperature A/D are supported as alternate remote inputs.

Enabling analog video out in rec mode is supported. AF Point Zoom must be disabled.

TESTED
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llibtst.lua
Extra long exposures (>64 sec), tested up to 300 sec.
 NOTE: exp_drv not implemented, < 1024s probably works without
Basic PTP: file transfer, play/rec, live view
script shooting hooks
Script zoom control
zebra - Thresholds must be ~1-2
Firmware update boot
raw/DNG - In P and AUTO, some special scene modes may be broken
jpeg quality override - Note this camera does not allow setting quality in 
 Canon UI. Default appears to be "fine"
script LED control - 0 = green power LED, 1 = AF lamp
SD override - Works in AF, MF and AFL
vidtest.lua
PTP remote shoot - Works in cont mode, does not crash when switchinbg to play
chdkptp camtests
Motion detection - 50-80ms response, average 61
Quick press - Overrides applied, raw saved when shooting without waiting for focus
ND override

KNOWN BUGS
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* Crashes on half shoot if AF Point Zoom is enabled with AV out in rec.

NOT IMPLEMENTED
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video controls (movie_rec task)

OTHER ISSUES
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DNG color matrix is copied from another cam, but usable