EVT2-matlab

MATLAB MEX interface for communicating with the EVT-2 HID device using HIDAPI.

This repository contains a Matlab binding to communicate with the EVT-2 (+derivatives) USB-device, developed by the Research Support group of the faculty of Behavioral and Social Science from the University of Groningen. The EVT-2 is a TTL event marking/TTL triggering device intended for computer-based psychology experiments.

Features

• Platform Independent: Works on Windows and Linux.
• Simple API: Direct commands for open, close, write, clear, set, pulse and read.
• Can open multiple EVT devices at once: use unique device handles to address the right device.

Prerequisites

Windows

1. Install the MATLAB add-on: MinGW-w64 compiler.
2. Run mex -setup in MATLAB and select the MinGW64 compiler.
3. Download and unzip the HIDAPI drivers https://github.com/libusb/hidapi/releases/tag/hidapi-0.15.0.
4. Copy hidapi.dll from inside x64 to the main directory. The file structure now should look like:

EVT2-matlab/
│
├── .git
├── include
├── x64
├── x86
├── build_evt2.m
├── evt2.c
├── evt2.h
├── evt_pulse.m
├── evt_test.m
├── .gitignore
├── hidapi.dll
├── LICENSE
├── listDevs.m
├── README.md
└── rsp_test.m

Linux (Ubuntu/Debian)

1. Install the HIDAPI development library:

   sudo apt-get install libhidapi-dev

2. Permissions: You typically need a udev rule to access HID devices without root. Create /etc/udev/rules.d/99-evt2.rules:

   SUBSYSTEM=="hidraw", ATTRS{idVendor}=="0808", ATTRS{idProduct}=="0001", GROUP="plugdev", MODE="0660"
   

   • reload rules: sudo udevadm control --reload-rules && sudo udevadm trigger

   • become member of the plugdev group sudo usermod -aG plugdev $USER

   • plugin the device

   • ls -l /dev/hidraw0 must give: r+w access to group crw-rw---- 1 root plugdev 241, 0 mei 4 14:33 /dev/hidraw0

EVT2-matlab/
│
├── .git
├── build_evt2.m
├── evt2.c
├── evt2.h
├── evt_pulse.m
├── evt_test.m
├── .gitignore
├── LICENSE
├── listDevs.m
├── README.md
└── rsp_test.m

Building the MEX file

A unified build script is provided. In the MATLAB Command Window, simply run:

build_evt2

The script will automatically detect your OS, locate the necessary headers/libraries, and produce the evt2 MEX file.

Usage Examples

% List all connected HID devices
devs = evt2('list');
listDevs(devs);

x = input('Enter a number: ');

% Open a device by its index from the list (returns a handle h)
h = evt2('open', x);

% Write a value to the device
evt2('write', h, 170); 

% Pulse a value (handle, value, duration_ms)
evt2('pulse', h, 255, 500);

% Read data with an optional timeout in ms (max 10,000ms)
% data = evt2('read', h, timeout_ms);
data = evt2('read', h, 1000);

% Flush the read buffer
evt2('flush', h);

% Close the device
evt2('close', h);

Example scripts

m-file	description
evt_pulse.m	shows how to use the pulse function
evt_test.m	example on how to address individual outputs
resp_test.m	waits for input from an EVT response box (RSP)