GPIO / Trigger / Strobe Interface

Isolated inputs and outputs by optical transformer.

Optocoupler basics

Open Diagram of basic optocoupler function

An optocoupler is a device using optical path to transfer an electronic signal between two circuits. It basically consists of a photodiode between pin 1 and 2 converting the input signal to light and a phototransistor converting the light again to electronic signal at pin 3 and 4. The optocoupler is useful in situations where one part of the circuit needs to be galvanically isolated from the other part to prevent damage or unwanted interference. It is used to prevent ground loops or to block voltage spikes. For effective use of the optocoupler it is important to control it using an independent power supply. When the external circuit is galvanically connected to the camera (eg. when reusing the camera's power to control the optocoupler), the optocoupler's protective function is eliminated.

Optocoupler parameters summary

Parameter	Input Value	Output Value

Parameter	Input Value	Output Value
Operating voltage	3.3 - 30 V	3.3 - 30 V
Input current	7.5 mA	< 100mA
External resistor requirement	No	Yes, output current must be limited to 100 mA
ON voltage level	> 4.5 V
OFF voltage level	< 1.5 V
OFF to ON delay	< 125 ns	750 ns
OFF to ON rise time (10 to 90%)		1.0-4.0 µs
ON to OFF delay	< 125 ns	2.4 – 25 µs
ON to OFF fall time (90 to 10%)		9.0 – 140 µs
OFF to ON jitter	± 5 ns	± 20 ns
ON to OFF jitter	± 5 ns	± 0.1 µs
	Open

Optocoupler inputs

iam is equipped with four optically isolated input lines. One input optocoupler is fully independent, the other three are connected with a common cathode (Section “I/O connector”) due to limited number of pins on the I/O connector. Each input line is protected by a current limiter circuit.

The optocoupler is guaranteed to be switched on (logical 0 input status) when the voltage applied to the input is in range of 3.3 - 30V (tolerance 10%). It is guaranteed to be switched off (logical 1 input status) when the applied voltage is under 2.0V. The input status is undefined between 2V and 3V, the input voltage must not exceed the 30V limit!

The input lines are using fast optocouplers: The propagation time is under 125 ns, for both rising and falling signal edge (assuming input signal with strongly steep edge). The exact switching speed may vary with temperature and the used input voltage level - the listed specifications are the worst case values.

Trigger input

Any of the available optocoupler inputs can be used for triggering. The input line mapping on the camera connectors is described in section Connector and cable description .

Schematic

Optocoupler outputs

iam is equipped with three optically isolated output lines. One output optocoupler is fully independent, the other two are connected with a common collector (Section “I/O connector”) due to limited number of pins on the I/O connector.

After power up, the optocoupler outputs are in high impedance state and they remain in that state until reconfigured from the software interface. Automatic reconfiguration at start up can be done by means of user sets.

The rising edge (switching to logical 1) propagation time is 750 ns, the falling edge propagation time is under 25 µs. The exact switching speed may vary with temperature and the used input voltage level — the listed specifications are the worst case values.

Strobe output

Any of the available optocoupler output can be used for strobe control. The output line mapping on the camera connectors is described in section Connector and cable description .

Schematic

SynView Transport Layer Features For IO/Strobe/Trigger

The feature and enum entry names mentioned in the diagram below

Block Diagram