Latency Checker

Updated September 23, 2014

Created September 23, 2014

Purpose

Simple Latency Measurement Application for Head Mounted Display. This project handles LED and light sensor to measure the latency from blinking to showing on the display.

Download

1. mbed repository
2. DesignSpark PCB files

How to Use

1. Put LED just in front of the camera and put sensor on the display in HMD.
2. Start a console terminal and connect to mbed.
3. Push mbed restart button to initialize.
4. Copyright appears and starts initialization. Initialization result indicates as follows;
   1. CAUTION ----- Strong back light flickering found. Set back light brightness maximum.
   2. Notice ----- Weak back light flickering found. Set back light brightness maximum.
   3. great! ----- It's ready for measure latency.
5. Latency will appear on the terminal.

Circuit

3.3V --- PT600T --- (sense) --- 10k --- GND

P16 --- [LED] --- GND

Voltage Flickering

Flickering found when LCD back light is dark. The program detect flickering and gives notice if large.

Monitor : EIZO ColorEdge CX270

Vp-p = 1V @ White area in paint brush (100cd/m2)

Vp-p = 0.4V @ black area

Photos

References

• mbed-dsp