Input Configuration
For GPI configuration, you have two signal modes available: Mode “Differential”, and mode "Single-ended". Mode "Differential" is the default mode.
In mode “Differential”, you can use the GPIs on the Front GPIO for receiving either up to 3 differential signals, or for receiving two differential signals and one single-ended signal.
In mode Single-ended”, you can use the GPIs on the Front GPIO for receiving up to 4 single-ended signals.
You can switch between the modes "Differential" and "Single-ended" using the command line tool as described in Configuring the Physical Properties of Trigger Signals.
Differential Mode (Default Mode)
In default configuration (“Differential” mode), all the six input pins of the Front GPIO are configured to receive differential signals (in pull-up mode):
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-> 1 differential signal (pin 8 +, pin 9 - ) | |
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-> 1 differential signal (pin 11 +, pin 12 -) | |
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-> 1 differential signal (pin 13 +, pin 14 - ) | |
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-> GPI voltage IN (4,5 - 28 V): The GPI voltage IN must be the same voltage as the signal source voltage. | |
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-> GPI GND |
Alternatively, you can (in default configuration) use pin pair 8/9 to receive one single-ended signal:
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-> 1 single-ended signal: You connect the single-ended incoming signal to the physical pin 9; Pin 8 is not connected. | |
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-> 1 differential signal (pin 11 +, pin 12 -) | |
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-> 1 differential signal (pin 13 +, pin 14 - ) | |
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-> GPI voltage IN (4,5 - 28 V): The GPI voltage IN must be the same voltage as the signal source voltage. | |
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-> GPI GND |
Single-Ended Mode
If you need more than 1 single-ended input signal, you can switch the GPIs of your Front GPIO into "Single-ended" mode. In "Single-ended" mode, the six input pins of the Front GPIO are configured to receive 4 single-ended signals:
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-> 1 single-ended signal | |
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-> 1 single-ended signal | |
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-> 1 single-ended signal (pin 12 not used) | |
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-> 1 single-ended signal (pin 14 not used) | |
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-> GPI voltage IN (4,5 - 28 V): The GPI voltage IN must be the same voltage as the signal source voltage. | |
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-> GPI GND |
How to switch between "Single-ended" and "Differential" mode, see Configuring the Physical Properties of Trigger Signals.
Custom Configuration “Pull-Down” |
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Both configurations (Differential and Single-ended) can be used in pull-up and pull-down mode. Default is the pull-up mode. If you want to use the inputs in pull-down mode, you can configure the pins accordingly, see Configuring the Physical Properties of Trigger Signals. |
Schematic Circuit Diagram Front GPIO:
Electrical Characteristics of the Physical Inputs:
Electrical |
Minimum |
Typical |
Maximum |
Unit |
---|---|---|---|---|
Supply voltage | 4.5 | 28 | V | |
Input threshold | 20% Supply Voltage | V | ||
Differential input offset voltage | 10 | mV | ||
Current at GPI pin | 4 | mA | ||
Total current at GPI voltage IN | 50 | mA |
Timing Characteristics of the Physical Inputs:
Timing |
Minimum |
Typical |
Maximum |
Unit |
---|---|---|---|---|
Propagation delay | 40 | 60 | 80 | ns |
Min. pulse width | 200 | ns | ||
Max. frequency | 2.5 | MHz |
Board Protection |
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LightBridge 2 ACL has been designed with a varistor which opens at an input voltage of 30V (on the GPIOs) to let the onboard surge protector get active to protect the board. At a total supply voltage of 36V, the electronic chips would become defective. |