# Ae3 csi trigger mode and auto exposure

**URL:** <https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849>\
**Category:** OpenMV Boards\
**Created:** [August 11, 2026, 11:59am UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849 "2026-08-11T11:59:27Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![chobitsfan](https://avatars.discourse-cdn.com/v4/letter/c/71c47a/32.png) [@chobitsfan](https://forums.openmv.io/u/chobitsfan)\
**Post date:** [August 11, 2026, 11:59am UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849/1 "2026-08-11T11:59:27Z")

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On AE3, when csi.IOCTL\_SET\_TRIGGERED\_MODE set to true, does the auto\_exposure() and auto\_gain() only change exposure time / gain when snapshot() called? And do I need to set framerate() when use trigger mode? Thank you very much

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**Author:** ![kwagyeman](https://yyz1.discourse-cdn.com/flex029/user_avatar/forums.openmv.io/kwagyeman/32/4_2.png) [@kwagyeman](https://forums.openmv.io/u/kwagyeman)\
**Post date:** [August 11, 2026, 8:58pm UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849/2 "2026-08-11T20:58:18Z")

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Yeah, those functions still do what they normally do. The camera just doesn’t do anything until snapshot is called because it’s in triggered mode.

There’s no frame rate in triggered mode; the frame rate is how fast you can trigger. The framerate() option itself does, though, set an upper limit. So, you should raise that, but the camera doesn’t take a picture until snapshot is called.

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**Author:** ![chobitsfan](https://avatars.discourse-cdn.com/v4/letter/c/71c47a/32.png) [@chobitsfan](https://forums.openmv.io/u/chobitsfan)\
**Post date:** [August 12, 2026, 2:55am UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849/3 "2026-08-12T02:55:51Z")

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Hi @kwagyeman Thank you for replying

> Yeah, those functions still do what they normally do. The camera just doesn’t do anything until snapshot is called because it’s in triggered mode.

I am sorry that I may not clearly express my question. In trigger mode, sensor only start pixel integration when snapshot() is called. If snapshot is called at 1hz, does auto\_exposure change exposure time at 1hz?

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**Author:** ![kwagyeman](https://yyz1.discourse-cdn.com/flex029/user_avatar/forums.openmv.io/kwagyeman/32/4_2.png) [@kwagyeman](https://forums.openmv.io/u/kwagyeman)\
**Post date:** [August 12, 2026, 5:15am UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849/4 "2026-08-12T05:15:25Z")

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Yes, exposure happens when the trigger pulses. AEC will update its internal settings based on what is seen in that image unless you force manual control.

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**Author:** ![chobitsfan](https://avatars.discourse-cdn.com/v4/letter/c/71c47a/32.png) [@chobitsfan](https://forums.openmv.io/u/chobitsfan)\
**Post date:** [August 12, 2026, 6:28am UTC](https://forums.openmv.io/t/ae3-csi-trigger-mode-and-auto-exposure/11849/5 "2026-08-12T06:28:24Z")

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Thank you for very helpful info