Description

Frame2TTL v3 is a device that measures the instant a computer monitor has completed drawing a new frame using an optical sensor (Renesas Electronics ISL76671). It outputs a 3.3V TTL pulse to indicate frame updates to other instruments. To drive the device, experimenters configure the patch of pixels under the sensor to alternate between minimum and maximum intensity with each frame (e.g. as implemented automatically in the PsychToolboxVideoPlayer plugin for Bpod). The output signal is used in Neuroscience to precisely align the frames of a visual stimulus with concurrently acquired physiology, functional microscopy and behavioral data.

Specifications

Processor

• ARM Cortex M7: NXP i.MX RT1060 Crossover as part of the Teensy 4.0 embedded computing platform
• 600MHz Clock Speed
• 1MB RAM
• Programmable in the Arduino language

Sensor

• Renesas Electronics ISL76671
• ISL76671 is a light to voltage converter IC. The chip consists of a photodiode array coupled to a pair of amplifiers that condition the signal to be directly digitized. The ISL76671 has spectral sensitivity similar to the human eye, and can be used in assays that also employ infrared illumination. The sensor has an excellent response latency of 250-350µs.

Sensor Mount

• The mount is 3D-printable. It is comprised of a circuit board holder, two arms and a pivoting foot.
• The mount clamps the sensor to the monitor face, blocking ambient light.
• Opposing silicone pads on the sensor and foot provide sufficient grip to keep the sensor in place.
• A light-attenuating film beneath the sensor's silicone pad ensures that the light signal will fall in the sensor's dynamic range.
• The mount is compatible with IPS monitors up to 25mm thick, with a bezel up to 1mm above the screen surface.

Output channels

• BNC connector 1: 3.3V TTL Logic indicates video frame changes
• BNC connector 2: Analog (0-4V) indicates the current sensor light level

Latency

• Frame2TTL signals intensity changes in < 0.5ms (typical).

Power supply

• Derived from a USB A to B-micro cable (included)

MATLAB Software

• A MATLAB interface class allows configuration of light intensity thresholds for frame detection.
• A simple command streams the light sensor's output to the screen, to help identify application-specific light levels and to aid with setting frame detection thresholds.

Bpod PsychToolboxVideoServer plugin

• The PsychToolboxVideoPlayer plugin for Bpod presents video stimuli to the test subject on a second monitor, while displaying a small "sync" patch on the screen edge to drive Frame2TTL.
• The sync patch alternates between 0 intensity and maximum intensity with each frame change during playback, causing a corresponding TTL level change on Frame2TTL's BNC output channel.

Material safety

• All parts are RoHS Compliant in our professional builds

Dimensions

• L: 6.0cm
• W: 5.0cm
• H: 2.0cm