Camera module Trigger Mode manual

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Camera Trigger Mode User Manual

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

Applicable Product models

The concept of image synchronization mode

Free Running

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

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 Data Sheet.

If using Xavier/TX2 , multiple cameras could be triggered by one signal.Pin definition:ADP_N1 Datasheet.

Triggger edge, trigger delay and trigger debouncer attribute supported.

triggeredge:trigger edge

tgdly:trigger delay

tgdebncr:debouncer

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 .

Exposure control and maximum frame rate in Trigger mode

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 .

Exposure time and Transmission time in Trigger mode

Ttgmin = Texp + Ttrans

Ttgmin:minimum trigger interval

Texp:exposure time

Ttrans:transmission time of one frame(from sensor to isp chip)

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

Texpmax = Ttgmin - Ttrans

Texpmax: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.

  • Texp: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.

  • Ttrans:transmission time of one frame(from sensor to isp chip)

In trigger mode, the time it takes for an image to be output from sensor, and the next trigger is accepted after the image output is completed.

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

Exposure time table in trigger mode
Video Format Ttrans(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

Delay in trigger mode

Ttotal = tgdly + Texp + Ttrans +Tisp+Tmipi

Ttotal :the total trigger delay is the time from the trigger signal to the complete image output through the MIPI signal. The following table is obtained by hardware measurement.

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

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

Tisp:image signal processing time.

Tmipi:MIPI transmission time.

Trigger delay measurement result
Video Format Texp(us) Ttotal(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