Waveform Feature Implementation for FRIB LLRF Controllers

TL;DR

This paper discusses implementing waveform feature storage in FRIB LLRF controllers, enabling real-time data buffering, monitoring, and diagnostics for RF signals at high sampling rates.

Contribution

It presents a detailed implementation of waveform data storage and retrieval in LLRF controllers, including memory management and interface design.

Findings

Successful storage of one second of RF data at 1.25 MHz

Enabling real-time data analysis and diagnostics

Implementation of flexible data monitoring modes

Abstract

Waveform feature is one of the requirements for the FRIB LLRF controllers. It is desired that the LLRF con-trollers store the internal data (e.g. the amplitude and phase information of forward/reverse/cavity signals) for at least one second of sampled data at the RF feedback control loop rate (around 1.25 MHz). One use case is to freeze the data buffer when an interlock event happens and read out the fast data to diagnose the problem. An-other use case is to monitor a set of signals at a decimated rate (user settable) while the data buffer is still running, like using an oscilloscope. The detailed implementation will be discussed in the paper, including writing data into the DDR memory through the native interface, reading out the data through the bus interface, etc.