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# ZED Link Duo GPIO Triggering

The ZED Link Duo [GMSL2](/docs/products/embedded/zed-link-capture-card/gmsl2#what-is-gmsl2) capture card allows you to synchronize external sensors by using triggering signals on the 10-pin 2mm pitch GPIO connector **J13**.

![](/_fern-img/5570179edf29c25535d37c78b4c522b5140593fec8f4f2bfa45a4dc32cc32f79.webp)![](/_fern-img/d324cc55e457b6956bcb4dafb381b88cc4261421f154397caaf5ecbdeabb4873.webp)

## Master mode - Trigger out

The ZED Link Duo capture card is configured to operate in **master mode** by default.

In any case, if you change mode, you can set the card back to master mode by setting `sync_mode=0` in the file `/etc/systemd/system/zed_x_daemon.service` and restarting the ZED X daemon service:

```bash
sudo sed -i 's/^sync_mode=./sync_mode=0/' /etc/systemd/system/zed_x_daemon.service # Set master mode
sudo systemctl daemon-reload # Reload systemd configuration
sudo systemctl restart zed_x_daemon.service # Restart ZED X daemon service
```

The default content of the file `/etc/systemd/system/zed_x_daemon.service` is as follows:

```bash
[Unit]
Description=ZED-X Daemon service
After=nvargus-daemon.service driver_zed_loader.service 
Requires=driver_zed_loader.service
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=1
User=root
StandardOutput=syslog
ExecStart=/usr/sbin/ZEDX_Daemon

# 0 = no sync(Default), 1 = master/slave mode, 2 = slave mode only
sync_mode=0 

[Install]
WantedBy=multi-user.target
```

The output synchronization signal is available on **pin #5** of the GPIO connector **J13** as soon as the Jetson™ device boots and the ZED Link [GMSL2](/docs/products/embedded/zed-link-capture-card/gmsl2#what-is-gmsl2) driver is installed.

* Connect the ground signal (Yellow - **GND**) to pin #9.
* Connect the trigger out signal (Green - **MFP0**) to pin #5.

![](/_fern-img/ee0640a75b2d19e58783ae35568a28df1f8e38db91f8cae0217df6235fcbfb86.webp)

### Triggering signal

The output trigger signal is a square wave, with its rising edge synchronized with the end of the exposure phase of the CMOS sensor.

The signal has a fixed **Amplitude** of 3.75V +/- 12%, while **Width** and **Frequency** change according to the frame rate setting of the camera.

#### Frame rate: 120 FPS - ZED X / ZED X Mini / ZED X Nano / ZED X One GS / ZED X One S

* Amplitude: 3.75V +/- 12%
* Width: 2.08 msec
* Frequency: 120 Hz
* Period: 8.33 msec

![](/_fern-files/stereolabs.docs.buildwithfern.com/99f1b9ebac6168656be9252341386194e5056bf0bb6607999d183018dc344db7/docs/products/embedded/zed-link-capture-card/images/zed-link-mono-OSC-120.png)

#### Frame rate: 60 FPS - ZED X / ZED X Mini / ZED X Nano / ZED X One GS / ZED X One S / ZED X One 4K

* Amplitude: 3.75V +/- 12%
* Width: 4.17 msec
* Frequency: 60 Hz
* Period: 16.67 msec

![](/_fern-files/stereolabs.docs.buildwithfern.com/0f9c565fbada2e728dc69f7e6b8f27ba300094d07c2ea37c528b7d015018b640/docs/products/embedded/zed-link-capture-card/images/zed-link-mono-OSC-60.png)

#### Frame rate: 30 FPS - ZED X / ZED X Mini / ZED X Nano / ZED X One GS / ZED X One S / ZED X One 4K

* Amplitude: 3.75V +/- 12%
* Width: 8.33 msec
* Frequency: 30 Hz
* Period: 33.33 msec

![](/_fern-files/stereolabs.docs.buildwithfern.com/31f4440ac4b04854bc6bde78a4f9fa8b2b642fa1bb098cd7d53193c8fe58f5e3/docs/products/embedded/zed-link-capture-card/images/zed-link-mono-OSC-30.png)

#### Frame rate: 15 FPS - ZED X / ZED X Mini / ZED X Nano / ZED X One GS / ZED X One S / ZED X One 4K

* Amplitude: 3.75V +/- 12%
* Width: 16.67 msec
* Frequency: 15 Hz
* Period: 66.67 msec

![](/_fern-files/stereolabs.docs.buildwithfern.com/59404121aaa2d27d2b9b5efd99126208e1df4b081b09e92f3a465c569763d417/docs/products/embedded/zed-link-capture-card/images/zed-link-mono-OSC-15.png)

## Slave mode - Trigger in

The ZED Link Duo capture card requires specific commands to switch to **slave mode**.

1. Set `sync_mode=2` in the file `/etc/systemd/system/zed_x_daemon.service` to enable the external trigger input.

   ```bash
   sudo sed -i 's/^sync_mode=./sync_mode=2/' /etc/systemd/system/zed_x_daemon.service
   ```

2. Reload the systemd configuration:

   ```bash
   sudo systemctl daemon-reload
   ```

3. Connect PIN #9 (`GND`) to the ground signal of the trigger source.

4. Connect PIN #5 (`DESER - MFP10`) to the trigger input signal, i.e., a 3.3V square wave signal.

5. Restart the driver by restarting the ZED X daemon service:

   ```bash
   sudo systemctl restart zed_x_daemon.service
   ```

To verify that the Slave configuration is active, run the command:

```bash
sudo dmesg | grep Sync
```

The output should be similar to:

```bash
[   XX.XXXXXX] sl_max96712 <bus>-<address>: Sync mode configured
```

You must use an external trigger signal with the following characteristics:

* Square wave
* Amplitude: 3.3V +/- 10%
* Frequency: Match the camera grab frame rate setting used with the ZED SDK - 15Hz, 30Hz, 60Hz, or 120Hz

![](/_fern-img/419179dcf35ad06e1d2d256cb8dae1a2cc9b230dd9b20106b0f48474ea2ba64b.webp)

## Master/Slave mode - Multiple ZED Link Duo cards synchronization

When using multiple ZED Link Duo capture cards on the same NVIDIA® Jetson platform, it's possible to synchronize them together by using the trigger out signal of one card as the trigger in signal for the other card.

The first [GMSL2](/docs/products/embedded/zed-link-capture-card/gmsl2#what-is-gmsl2) deserializer will automatically be configured as **master**, while the second one will operate in **slave** mode.

1. Set `sync_mode=1` in the file `/etc/systemd/system/zed_x_daemon.service` to enable the master/slave mode.

   ```bash
   sudo sed -i 's/^sync_mode=./sync_mode=1/' /etc/systemd/system/zed_x_daemon.service
   ```

2. Reload the systemd configuration:

   ```bash
   sudo systemctl daemon-reload
   ```

3. Connect together the PIN #9 (`GND`) of both ZED Link Duo cards.

4. Connect the PIN #5 (`DESER - MFP10`) of the first card to the trigger input signal PIN #5 (`DESER - MFP10`) of the second card.

5. Restart the driver by restarting the ZED X daemon service:

   ```bash
   sudo systemctl restart zed_x_daemon.service
   ```