Teensy 4.1 USB Host → BioSemi USB Trigger Interface: Serial data visible in pc termite, but not ActiView

[phb]

I'm developing a Teensy 4.1-based trigger system for ERP experiments using the BioSemi USB Trigger Interface. Codes are successfully transmitted but not appearing in ActiView.

Setup:
- BioSemi Active 2.5 system
- BioSemi USB Trigger Interface (serial-to-parallel converter)
- Teensy 4.1 with USB Host capability

What Works:
- Teensy USB Host → USB-RS232 → RS232-USB → PC/Termite
- Termite shows correct codes: 115200 baud, 8N1, no flow control
- Sending single-byte triggers (1-255, never 0)

What Doesn't Work:
- Teensy USB Host → BioSemi USB Trigger Interface → ActiView
- No triggers appear in ActiView trigger display

Code Characteristics:
- Single bytes sent via USBSerial (USBHost_t36 library)
- 2ms minimum interval between triggers
- Trial markers use two-byte sequence: 'T' (0x54) + trial number
- All codes guaranteed non-zero (1-255 range)

Questions:
1. Does the bioesemi interface require specific baud rate or other settings ?
2. Does the USB Trigger Interface expect any initialization sequence?
3. Has anyone successfully used a microcontroller as USB host with this device?

[Gerben]

I have no experience with microcontrollers running USB host controllers, the usb trigger interface i can help you with.
The setup that you describe sounds like it should work, did you verify if you receive triggers when you send triggers from a pc with termite to Actiview?

1. Does the bioesemi interface require specific baud rate or other settings ?

Yes, the Biosemi USB trigger interface only works with the following settings
Data Rate: 115200
Data Bits: 8
Stop Bits: 1
Parity: none
Flow Control: off
https://www.biosemi.com/faq/USB%20Trigg ... 0cable.htm

2. Does the USB Trigger Interface expect any initialization sequence?

No, only a single byte (0x01 - 0xFF) without trailing "/n, /r or end of string" characters

3. Has anyone successfully used a microcontroller as USB host with this device?

Not that we know of but let me ask a counter question?
why do you not connect the io pins of your microcontroller directly to the trigger connector without using the USB trigger interface?
The USB receiver is 3,3v compatible (5v internal pull-ups but can be limited to 3,3v with external zener diode).
https://www.biosemi.com/faq/trigger_signals.htm