How are stimulator trigger signals handed by BioSemi hard and software ?
 
The most common situation is when triggers from a stimulation PC are being sent to an acquisition PC.
This can be done by using the BioSemi USB Trigger Interface. https://www.biosemi.com/faq/USB%20Trigger%20interface%20cable.htm
The BioSemi Trigger Interface and the BioSemi USB Receiver will not introduce any significant delay or jitter, but the Stimulation PC with its USB output will introduce jitter and delay. If one wants to check the timing accuracy of the sent triggers then one can do this by recording the visual or auditory stimuli direct with a Photocell or Microphone. The Photocell or Microphone is plugged into the Ergo/AUX input of the AD-box (no delay, no jitter)

There are 3 different ways to add input trigger events to the ActiveTwo acquired data:
   
1)

To the Ergo/AUX input of the AD-box.
If your trigger is NOT connected to a mains powered source, then you may connect this trigger to the Ergo/AUX input of the AD-box.
Mains powered equipment, or equipment which is connected to mains powered equipment may NEVER be connected to the isolated parts (AD-box, electrodes, subject)
When you want to connect mains powered sources to the Ergo/AUX input of the AD-box, then this should be done by using the the optional Ergo Optical Cable.
The Ergo Optical Cable makes it possible to connect mains powered sources to the Ergo/AUX input.

You may for example connect a Response Switch to the Ergo/AUX input of the AD-box. The subject will press the button of the Response Switch on a certain task.
With this setup, the maximum delay/jitter of your trigger is limited to 1 sample. At a sample-rate of 16kHz, the maximum delay/jitter would thus be 62uSec.

A maximum of 2 Response Switches can be connected to the Ergo/AUX of the Active2/Active2.5 AD-box. The Active3 system can have 6 Response Switches connected.
ActiView can add the trigger events from the Response switches to Trigger Inputs 9&10 of the BioSemi USB Receiver on 3 different ways.
In the configuration file "Default.cfg" (located in the ActiView directory) 3 different modes can be chosen (standard mode, Ergo mode and Switch mode)
 
"RespSwitch=0 //0: standard, 1: ergo 1 & 2 coupled to trigger 9 & 10, 2: switch input coupled to trigger 9 & 10"

0: STANDARD MODE: Triggers 9&10 (as shown in ActiView) will be equal to the triggers offered at trigger inputs 9&10 (on the BioSemi USB Receiver).
The Ergo signals are not directed to bits 9&10. At this setting, bits 9&10 respond exactly the same as all other trigger bits.
This setting should be chosen if there is no ERGO or SWITCH installed.

1: ERGO MODE: Triggers 9&10 (as shown in ActiView) will be equal to Response Switches 1&2 at the ERGO input.
Use this setting when your AD-box has an ERGO input installed. (red ERGO sticker on the front of AD-box)
With this setting, the analog value of Ergo 1 and Ergo 2 is converted to a 1 bit digital value and directed to Triggers 9&10.
The Response switches connected to the Ergo inputs will now be shown at Trigger bits 9&10.
When nothing is connected to the Ergo inputs, then the high impedance inputs of the Ergo's will be floating, probably resulting in random triggers at Triggers 9&10.
In this mode Response Switches 1&2 will be output to Trigger outputs 1&2 at the USB Receiver.

2: SWITCH MODE: Triggers 9&10 (as shown in ActiView) will be equal to the Response Switches 1&2 connected at the SWITCH input at the front of the AD-box.
Use this setting when your AD-box has a SWITCH input installed. (red Switch sticker on the front of AD-box)
The Response switches connected to the SWITCH inputs will now be shown at Trigger bits 9&10.
In this mode Response Switches 1&2 will be output to Trigger outputs 1&2 at the USB Receiver.

Please note that the ERGO/Switch inputs on the AD-box should never be connected to anything which is mains powered. Connecting mains powered signals to the ERGO/Switch inputs will destroy the isolation of the isolated part of the system (the subject and AD-box).

   
2) Trigger input/output connector on the BioSemi USB Receiver.
These trigger inputs should never be connected to any of the isolated parts of the system (AD-box, electrodes, subject). Doing so will significantly drop the isolate rejection mode, and common rejection mode, which will lead to hum. Please see the below table for the pin layout of the 37 pin Sub-D connector at the USB Receiver.
You may for example connect the trigger cable coming from your stimulation PC to the trigger input/output connector of the BioSemi USB Receiver.
With this setup, the maximum delay/jitter of your trigger is limited to 1 sample. At a sample-rate of 16kHz, the maximum delay/jitter would thus be 62uSec.
   
3) By pressing the Function keys:
Function key F1 is routed to Trigger input 09.
Function key F2 is routed to Trigger input 10
Function key F3 is routed to Trigger input 11
Function key F4 is routed to Trigger input 12
Function key F5 is routed to Trigger input 13
Function key F6 is routed to Trigger input 14
Function key F7 is routed to Trigger input 15
Function key F8 is routed to Trigger input 16		 The keyboard Function Keys F1-F8 are logically 'ored' with the USB Trigger inputs 9-16. Inside the USB receiver there are 'Pull-up' resistors, so without anything connected to the USB trigger input/output port, all 16 trigger inputs will be 'high'.
In order to enable/have the Function Keys work, you will have to connect trigger inputs 9-16 to ground. The 'Presentation' cable delivered by BioSemi has internally shorcircuited Trigger inputs 9-16 to ground, so connecting the BioSemi 'Presentation' cable to the USB receiver will also make the Function Keys visible.




   

The ActiveTwo USB receiver has 16 independent trigger inputs and 16 independent trigger outputs (TTL level, 37-pole sub-d connector on the front panel of the receiver).
The inputs all have a 'Pull-up' resistor of 10 Kohm to 3.3 Volt. So if the trigger inputs are left unconnected they will be high.
The input triggers are mixed with the digital data coming from the AD-box. The input triggers are saved in an extra channel (the status channel), with the same sample rate as the electrode channels. So, the timing of the trigger inputs is accurate to the time period of a sample.
The trigger outputs can be controlled by software. ActiView Light (developer software) has a LabVIEW routine integrated which is able to control the trigger outputs.
Because the trigger inputs are located at the receiver, the trigger inputs and connected trigger equipment remains completely galvanically isolated from the front-end and the subject, this ensures that the trigger equipment can not cause any additional interference and provides optimal subject safety.
Because our acquisition software saves the electrode signals and trigger signals in .BDF (BioSemi Data Format), off-line ERP analysis can be performed with one of the many available third-party software package that are compatible with the .BDF format. Manufacturers who support the .BDF format automatically read our digital trigger format. No old fashioned setting of analog trigger levels etc is needed.

ActiView always automatically saves all 16 Triggers in an extra channel. It is not possible to NOT save the triggers. (to prevent any user mistake)

In ActiView, the incomming 16 trigger lines can be displayed on several ways.
At the configuration tab-page you can select for example to display the triggers on an Analog way or on a Decimal way.
When the 16 trigger input lines are display on an Analog way, each of the individual 16 trigger inputs will be displayed as a separate bit.
You can use the "Analog" mode to inspect unexpected trigger behavior.
In "Digital" display mode, the triggers will be displayed as 2 groups on 8-bit numbers (lines 1-8 and lines 9-16), each trigger group will have a value between 0 and 255.

In the tables below you can find the connections of the trigger input and a description of the Status channel.

All the Trigger inputs have internal 10 kOhm pull-ups, thus the triggers are normally "on".
 

 

 

 

 

 

 

 

 

 

37 pin female sub-D (USB interface)
Status channel information
Pin01
Trigger input 1

Trigger inputs 1-8 can also be used to control starting and stopping of saving data to disk. The button "Pause save" is controlled by 2 reserved trigger codes. These (8-bit) codes are defined in the CFG file. Trigger edges unlock or lock the "pause save" button, manual control of the pause button overrides the trigger pulses. Example of .cfg text:
PauseOff="254 //-1 is disabled, 0-255 is enabled"
PauseOn="255 //-1 is disabled, 0-255 is enabled"

Note that when the trigger inputs are not connected, they will be digital "1", so with the above .cfg, toggling trigger 1 and leaving the other pins unconnected, the pause button will switch on/off.
Pin02
Trigger input 2
Pin03
Trigger input 3
Pin04
Trigger input 4
Pin05
Trigger input 5
Pin06
Trigger input 6
Pin07
Trigger input 7
Pin08
Trigger input 8
Pin09
Trigger input 9
 Different settings of "RespSwitch" (Standard mode, Ergo mode, Switch mode) will change the behavior of Trigger input 9&10.(also in the BDF file)
Pin10 Trigger input 10
Pin11 Trigger input 11  
Pin12 Trigger input 12  
Pin13 Trigger input 13  
Pin14 Trigger input 14  
Pin15 Trigger input 15  
Pin16 Trigger input 16  
Pin17 Trigger output 1 When setting "RespSwitch" at "Ergo mode" (as described above), then Response Switches Trigger info is also placed at Trigger output 1&2. 
Pin18 Trigger output 2
Pin19 Trigger output 3  
Pin20 Trigger output 4  
Pin21 Trigger output 5  
Pin22 Trigger output 6  
Pin23 Trigger output 7  
Pin24 Trigger output 8  
Pin25 Trigger output 9  
Pin26 Trigger output 10  
Pin27 Trigger output 11  
Pin28 Trigger output 12  
Pin29 Trigger output 13  
Pin30 Trigger output 14  
Pin31 Trigger output 15  
Pin32 Sample-rate clock  
Pin33    
Pin34    
Pin35    
Pin36 5 Volt Can deliver maximum 100 mA.
Pin37 Ground  
Bit 00 (LSB)
Trigger Input 1 (High = trigger on)
Bit 01
Trigger Input 2 (High = trigger on)
Bit 02
Trigger Input 3 (High = trigger on)
Bit 03
Trigger Input 4 (High = trigger on)
Bit 04
Trigger Input 5 (High = trigger on)
Bit 05
Trigger Input 6 (High = trigger on)
Bit 06
Trigger Input 7 (High = trigger on)
Bit 07
Trigger Input 8 (High = trigger on)
Bit 08
 Trigger Input 9 (High = trigger on)
Bit 09
 Trigger Input 10 (High = trigger on)
Bit 10
 Trigger Input 11 (High = trigger on)
Bit 11
Trigger Input 12 (High = trigger on)
Bit 12
Trigger Input 13 (High = trigger on)
Bit 13
 Trigger Input 14 (High = trigger on)
Bit 14
Trigger Input 15 (High = trigger on)
Bit 15
 Trigger Input 16 (High = trigger on)
Bit 16
High when new Epoch is started
Bit 17
Speed bit 0
Bit 18
Speed bit 1
Bit 19
Speed bit 2
Bit 20
High when CMS is within range
Bit 21
Speed bit 3
Bit 22
High when battery is low
Bit 23 (MSB)
High if ActiveTwo MK2