Issue Synchronizing 4x OAK-FFC AR0234 M12 Cameras via External Trigger

jjfink

I’m working with four OAK-FFC AR0234 M12 cameras connected to a single OAK-FFC-4P board, and I’m trying to synchronize them precisely—similar to how synchronization is typically handled with OV9782 sensors.

Since the AR0234 sensors cannot generate their own trigger signals, I’m using a Raspberry Pi GPIO with a voltage divider to provide the external trigger. This setup works reliably with my IMX477 boards.

Because the AR0234 boards don’t have an XVS pad, I’m feeding the trigger signal through the PSBRS cable, as shown in the image below. The pulse length is 1 ms, and I’ve verified the signal using an oscilloscope—it’s clean and consistent.

Despite this, the cameras do not seem to be synchronizing properly, and I’m not seeing synchronized image output.

Has anyone successfully synchronized AR0234 sensors using this method? Is there anything I might be missing in terms of wiring, signal configuration, or firmware?

Im using the current dark modules not the old green ones. Are these ones also using 1,8V IO Voltage or a higher one I can see a 2,6V testpoint on the modules.

jakaskerl

jjfink
Let me check today, I'll get back to you.

Thanks,
Jaka

jakaskerl

jjfink
Which board revision and which sockets?

Thanks,
Jaka

jjfink

Its an OAK-FFC-4P DD2090 R3M1E3. I also noticed that it works if I trigger the Board with this Onboard Script

## Script Node to trigger the Sensors

## No Pi Need to be connected

FPS = frame_rate

script.setScript("""

import time

import GPIO

# Script static arguments

fps = %f

calib = Device.readCalibration2().getEepromData()

prodName = calib.productName

boardName = calib.boardName

boardRev = calib.boardRev

node.warn(f'Product name : {prodName}')

node.warn(f'Board name : {boardName}')

node.warn(f'Board revision: {boardRev}')

node.warn(f'Camera FPS : {fps}')

revision = -1

# Very basic parsing here, TODO improve

if len(boardRev) >= 2 and boardRev[0] == 'R':

revision = int(boardRev[1])

node.warn(f'Parsed revision number: {revision}')

# Defaults for OAK-FFC-4P older revisions (<= R5)

GPIO_FSIN_2LANE = 41 # COM_AUX_IO2

GPIO_FSIN_4LANE = 40

GPIO_FSIN_MODE_SELECT = 6 # Drive 1 to tie together FSIN_2LANE and FSIN_4LANE

if revision >= 6:

GPIO_FSIN_2LANE = 41 # still COM_AUX_IO2, not PWM capable

GPIO_FSIN_4LANE = 42 # also not PWM capable

GPIO_FSIN_MODE_SELECT = 38 # Drive 1 to tie together FSIN_2LANE and FSIN_4LANE

# Note: on R7 GPIO_FSIN_MODE_SELECT is pulled up, driving high isn't necessary (but fine to do)

# GPIO initialization

GPIO.setup(GPIO_FSIN_2LANE, GPIO.OUT)

GPIO.write(GPIO_FSIN_2LANE, 0)

GPIO.setup(GPIO_FSIN_4LANE, GPIO.IN)

GPIO.setup(GPIO_FSIN_MODE_SELECT, GPIO.OUT)

GPIO.write(GPIO_FSIN_MODE_SELECT, 1)

time.sleep(1)

period = 1 / fps

active = 0.001

node.warn(f'FPS: {fps} Period: {period}')

withInterrupts = False

if withInterrupts:

node.critical(f'[TODO] FSYNC with timer interrupts (more precise) not implemented')

else:

overhead = 0.003 # Empirical, TODO add thread priority option!

while True:

GPIO.write(GPIO_FSIN_2LANE, 1)

time.sleep(active)

GPIO.write(GPIO_FSIN_2LANE, 0)

time.sleep(period - active - overhead)

"""% (FPS))

jakaskerl

jjfink

GPIO6 should be the line to connect the 4L fsin to 2L fsin, but since you are already triggering on both (COM_AUX_IO2 and FSIN_4LANE) this is not needed. Not sure what your script is setting and where you got it from - the numbers seems incorrect.

You need to make sure that GPIO40 is disabled - and all sensors are set to INPUT mode (FrameSyncMode).

Thanks,
Jaka

jjfink

With my last post, I meant that it works when I trigger the sensors using a pulse generated by the OAK FFC-04 itself, as shown in Erik’s post without the pico pi.

https://discuss.luxonis.com/d/3504-hardware-timer-on-oak-ffc-3p-for-ar0234-stereo-pair/7

However, it does not work with my external Raspberry Pi solution, which is important since I want to use an external sync source.

jakaskerl

jjfink

#!/usr/bin/env python3

from calendar import c
import cv2
import depthai as dai

# Create pipeline
pipeline = dai.Pipeline()

# Define source and output
camRgb = pipeline.create(dai.node.ColorCamera)
xoutVideo = pipeline.create(dai.node.XLinkOut)
xoutVideo.setStreamName("video")

# Properties
camRgb.setBoardSocket(dai.CameraBoardSocket.CAM_A)
camRgb.setResolution(dai.ColorCameraProperties.SensorResolution.THE_1200_P)
#fps 30
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.initialControl.setExternalTrigger(1,0)

xoutVideo.input.setBlocking(False)
xoutVideo.input.setQueueSize(1)

# Linking
camRgb.video.link(xoutVideo.input)

# Connect to device and start pipeline
with dai.Device(pipeline) as device:

    video = device.getOutputQueue(name="video", maxSize=1, blocking=False)

    while True:
        videoIn = video.get()

        # Get BGR frame from NV12 encoded video frame to show with opencv
        # Visualizing the frame on slower hosts might have overhead
        cv2.imshow("video", videoIn.getCvFrame())

        if cv2.waitKey(1) == ord('q'):
            break

I then used a signal generator (1.8V, 100us pulse, 10Hz). Works on the AR0234 , - but caveat: If you remove the generator, the camera continues streaming at the FPS set inside the pipeline. I wasn't able to figure out a way to make it stop streaming altogether (while OV9282 works as expected). Nevertheless, both the CAM_A FSIN1 pad as well as the PSRBS worked.

Tested Erik's script as well, it uses a different functionality and it works if all 4 lines are connected together (gpio6).

Thanks,
Jaka