Speed tuning

A project log for WizYasep

LED screen controller over Ethernet... among others ! It's a Wiznet IP controller with a A3P250 FPGA and I/Os.

Yann Guidon / YGDESYann Guidon / YGDES 09/24/2016 at 13:340 Comments

The WizYasep accomodates varying channel counts with the help of a variable frequency generator. The less channels to drive, the longer the period and the higher the value that is loaded in the digital predivider.

This predivider value (and other paramaters) are stored in a precomputed table, which is hardwired in the FPGA. A change in the channel count will also update the clock frequency accordingly.

There are cases where the frequency must be tuned. For example, when using the WS2811 in slow mode (400kbps) so the predivider value should be updatable. A prediv register should be written from the Flash contents or the network. This is one of the planned updates to the firmware.