‍Affected Applications

‍This discussion affects c-pod users where timing over a period of time must be better than 1%. Examples are:

• Using the pulse table commands to auto-generate markers over minutes or hours.
• On Universal c-pod and c-pod for MindWare, using the c4 command to time-stamp the input, typically over the course of an experiment.

‍The more typical application where you send event markers are not affected. In those situations, pulses produced by c-pod are typically too short for timing to be impacted.

‍Why

‍Cedrus devices are smart products powered by a microprocessor, which requires an oscillator. On our larger products, namely StimTracker, Riponda, RB-x40 response pads, and Lumina, we use a quartz oscillator. This is a very precise electronic component.

‍The initial requirement of c-pod was to provide simple functions within the smallest size possible (e.g. c-pod for actiCHamp). Due to space constraints, a simpler but less accurate RC oscillator was used. As c-pod’s capabilities have grown, the requirement for timing accuracy has also grown.

‍Calibration

‍Cedrus has developed a method for calibrating c-pod so timing remains precise. This method consists of three commands in firmware version 2.3.5 or later and code running on the computer. The code calculates the timing adjustments that are needed and then stores them in flash memory. This would be a one-time operation; you do not need to calibrate before the start of every experiment.

‍The Commands

‍