Mechanism to synchronize led with the camera sensor exposure

Robotics & Edge Computing Jetson & Embedded Systems Jetson AGX Xavier
1

Hi,

Is there a way to synchronize a led to the camera sensor exposure? For example, can I capture the trigger to indicate the beginning of a frame capture and start a GPIO (like gpio424, gpio393, gpio344) on the NVIDIA Jetson AGX Xavier GPIO Header Pinout? I want to achieve something like the following:

Timing-diagram
Timing-diagram800×494 36.2 KB

3

hello nouuata,

may I know what’s your actual use-case, are you having the use-case like a flash light?

4

Hi @JerryChang

yes, we can classify it as a high frequency flash light synchronized with the beginning of frame capture. In the best scenario, we would like to be able to control the strobe light intensity (PWM) and on/off timing minimizing the volatility of the control communication to a few microseconds. If this is not possible we can use a list of ‘flash patterns’ and less frequent control updates. We already achieved this with Arduino as a led control board, we want to port this on Jetson AGX now.

Thanks!

5

hello nouuata,

would like to confirm you’re not using flash light to compensate the scene luminance for image capture.

you may look into Xavier’s VI driver, it’s vi5_fops.c
there’re two threads for frame captures, it’s a thread to enqueue sensor frame into capture buffer, another thread to dequeue for the user-space.
so, this is one frame become available that you may having implementation for your use-case.
for example,

static int tegra_channel_kthread_capture_dequeue(void *data)
{
        while (1) {
...
                        buf = dequeue_dequeue_buffer(chan);
                        if (!buf)
                                break;

                        vi5_capture_dequeue(chan, buf);
                }
6

I got it. Thanks!