Refresh Rate

Refresh rate refers to the maximum speed at which all the pixels can be updated. This is usually quantified in frames per second (FPS), and typically varies from about 20 FPS at the low end up to 100+ FPS at the high end.

What Affects Refresh Rate?

Refresh rate is affected by several factors, all of which contribute to the overall refresh rate. The most significant of these factors are:

  1. Efficiency of the sending software, and what refresh rate this can achieve.
  2. Processing time of the PixLite’s CPU.
  3. The maximum number of pixels connected on an individual output.
  4. The total number of pixels connected to a controller.
  5. Data (or clock) speed of the pixel protocol.

Sending Software Limitations

If your sending software is slow then it probably won’t matter whether you’re using a clocked pixel data rate or not. A simple example would be two PixLite systems operating from the same sending software. One PixLite system is configured to drive 100 x WS2812B (data-only) pixels and the other drives 100 x APA102 (clocked) pixels. If the sending software only transmits at 20 FPS, then it would be the limitation, and so both pixel controllers will achieve the same overall refresh rate, regardless of the difference in data speed between APA102 and WS2812B pixels.

This is why it is important to have sending software that is efficient and configured to operate at a suitable data rate for the lighting patterns you are generating. This ensures that your overall refresh rate is not limited by a slow incoming data rate. Conversely it is important to make sure that the PixLite can output fast enough to keep up with the incoming data rate.

Pixel Limitations

It stands to reason that the more pixels you have on an output, the longer it will take to update them all. The PixLite will send data to all outputs simultaneously and can only send the next frame when all the data has been transmitted on all outputs. This means that the time it takes a frame to be fully transmitted will largely depend on the output with the highest pixel count. If all outputs have an even distribution of pixels, this will help speed up your refresh rate. Using the expanded mode feature can be useful in keeping this number of pixels on an output down, which can increase the overall refresh rate.

If your incoming data rate is high, and your pixels are evenly spread, then the data speed of your pixels can affect refresh rates. Data-only protocols, such as WS2812B, can have a slower maximum refresh rate than a clocked pixel protocol such as APA102, when working with the same number of pixels. If there are no other limitations and your pixel count is fixed, then a clocked pixel type can typically result in data speeds between 1.5 to 3.5 times faster when used with a PixLite controller, resulting in a faster overall refresh rate.

Categories: Technical Notes