Camera module Trigger Mode manual

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This AN mainly introduces the trigger mode of global shutter camera module, including hardware trigger and software trigger.

1 Applicable Product models

CS-MIPI-SC132

2 The concept of image synchronization mode

2.1 Free Running

In this mode, the camera module runs on its own.

2.2 Hardware Trigger

In this mode,The Trigger IO pin is used as the trigger signal, and the module begins to expose and output the image after receiving the trigger signal.

Pin definition：CS-MIPI-SC132 DataSheet

Triggger edge, trigger delay and trigger debouncer attribute supported.

triggeredge ：trigger edge

tgdly：trigger delay

tgdebncr：debouncer

2.3 Software Trigger

In this mode，Use the I2C register to trigger an image.

striggerone: trigger an image

Note：The above instructions refer to CS Serial I2C setting .

3 Exposure control and maximum frame rate in Trigger mode

3.1 Configuration of exposure and gain in Trigger mode

In trigger mode, it is recommended that users use manual exposure. Of course, the automatic exposure mode can also be used,

but because the AE algorithm needs to go through some frames to converge, the exposure effect of the first few frames will not be good.

expmode：exposure mode setting

metime：manual exposure time

meagain：manual analog gain

medgain：manual digital gain

You can use the expostate instruction to read out the current exposure time and gain value in automatic mode as a reference.

Note：The above instructions refer to CS Serial I2C setting .

3.2 Exposure time and Transmission time in Trigger mode

T_{tgmin =} T_exp + T_trans

T_tgmin minimum trigger interval

T_exp： exposure time

T_trans：transmission time of one frame

Accordingly, if the minimum trigger interval is known, the maximum allowable exposure time is:

T_{expmax =} T_{tgmin -} T_trans

T_expmax maximum exposure time

If the time interval between the current trigger signal and the previous trigger signal is smaller than the minimum interval time,

the sensor will ignore the current trigger signal.

T_exp exposure time

Users can set it to automatical or manual.

expmode is auto : set max exposure time via aetime.

expmode is manual : set exposure time via metime.

T_trans ： transmission time of one frame

The transmission time of a frame is related to the current resolution mode.

Exposure time table in trigger mode
Video Format	T_trans(ms)	Max Framerate	Maximum exposure time to guarantee maximum framerate（ms）
1280x1080 1080x1280	18.67	45	3.55
1280x720 720x1280	14.94	60	1.73
640x480 480x640	7.65	120	0.68

4 Delay in trigger mode

T_total = tgdly + T_{exp +} T_{trans +}T_isp+T_mipi

T_total ：the total trigger delay is the time from the trigger signal to the complete image output through the MIPI signal.

tgdly: trigger delay time, the following measurements are configured to 0. tgdly is valid only for Hardware trigger mode.

T_exp : exposure time，the following is based on the actual values read by expostate.

T_isp：image signal processing time.

T_mipi: MIPI transmission time.

Trigger delay measurement result
Video Format	T_exp（us）	T_total(ms）
1280x1080	1000	45.80
1080x1280	1000	43.20
1280x720	1000	35.20
720x1280	1000	33.40
640x480	1000	18.00
480x640	1000	17.20