External Triggers

Some of Prophesee products and sensors support external triggering (input or output signals) allowing to control the sensor and synchronize data between several devices.

Supported Trigger Functions

Prophesee cameras allow to capture external Trigger In transitions along with the sensor native data stream.

Prophesee cameras can also provide an external Trigger Out signal with a programmable period and pulse.

Trigger In Principle

The following diagram depicts Trigger In signal detection and the corresponding sensor data flow insertion.

Trigger In principle diagram

A block circuitry is implemented to detect Trigger In signal transition on the sensor module.

When a complete transition cycle is occurring, a specific rising-edge event is generated first (shown as the orange/yellow box) followed by a specific falling edge event (shown as the red box).

The 2 events are occurring while the sensor is streaming its data (shown by blue boxes). The 2 data flows are merged together and provided to the sensor output transmission interface.

Trigger In circuitry is able to detect up to 1 MHz clock transition. The minimum requirement for pulse width/period is 500/1000 ns. There is no limitation on pulse width duration and frequency.

This Trigger In function can be enabled/disabled at the camera interface level using Metavision::I_TriggerIn::enable() method in Metavision HAL Metavision::I_TriggerIn facility.

Trigger Out Principle

Prophesee cameras have an ability to provide an external Trigger Out signal for which the period and the pulse width is programmable.

Trigger Out principle diagram

Trigger Out functionality uses an internal time reference with 1us resolution, so that the maximum signal frequency is 0.5 MHz.

Both signal frequency and duty cycle can be adjusted by user using functions in Metavision HAL Metavision::I_TriggerOut class:

Trigger Out pulse width value shall be at least one time unit less than the pulse period; otherwise, no trigger out pulse will be generated.

This function can be enabled/disabled at the camera interface level.

Prophesee Evaluation Kit (EVK) Trigger Interface

The external connection interface for Prophesee Evaluation Kit is represented below:

../../_images/EVK_triggers_cropped.jpg

Pin #

Function

0

TRIGGER_OUT/EXT_SYNC_CLK_OUT (1.8V)

1

GND

2

EXT_SYNC_CLK_IN (1.8V)

3

GND

4

TRIGGER_IN_P - opto-coupled

5

TRIGGER_IN_N - opto-coupled (usually connected to GND)

Electrical Specification

Trigger In

On this system, the TRIGGER_IN is an opto-coupled 5V compatible input (typical drive strength required for driving circuit is of at least 7mA).

Note

To use the TRIGGER_IN signal to the camera, the pin #4 (TRIGGER_IN_P) and the pin #5 (TRIGGER_IN_N) must be connected.

Electrical Feature

Min

Typ

Max

Logic Low voltage

0.0V

0.0V

1.0V

Logic High voltage

3.6V

5.0V

5.0V

Required Input Strength

7mA

15mA

Trigger Out

The TRIGGER_OUT output is 1.8V (LVCMOS). Beware that the maximum output drive strength is limited to 4mA.

Output Voltage

Max Output Drive

1.8 V

4 mA

Note

The EVK pin used for Trigger Out is pin #0. The associated GND pin is the pin #1 (next to the Trigger Out pin).

The TRIGGER_OUT pin does not have any internal pull-up resistor on the line. The voltage for TRIGGER_OUT is fixed to 1.8V, and the associated maximum drive strength is of 4mA.

The two remaining pins (6,7) are related to the IMU of the EVK. The device can also act as an I2C master for additional sensors. The SDA (pin 6) and SCL (pin 7) signals required are brought to a pad on the top of the board.

Reference Mating Connector

The trigger mating connector is compatible with 0.1” jumper wires.

Supplier reference: http://technologicalarts.ca/breakout-cables