Distributed continuous event - based data acquisition using FlexRIO FPGA

High - speed event driven acquisition is normally performed by ADC boards with a given number of pre and post trigger samples that are recorded upon the occurrence of a hardware trigger. A direct physical connection is therefore required between the source of event (trigger) and the ADC because any other software - based communication method would introduce a delay in triggering that would turn out to be not acceptable in many cases. This paper proposes a solution for the relaxation of the event communication time that can be in this case carried out by software messaging (e.g. via a LAN) provided that the system components are synchronized in time (e.g. using IEEE 1588 synchronization mechanism). The information about the exact event occurrence time is contain ed in the software packet sent to communicate the event and is used by the ADC FPGA to identify the exact sample in the ADC sample queue. The length of the ADC sample queue will depend on the maximum delay in software event message communication time. A pr ototype implementation using a National FlexRIO FPGA board connected with an ADC device is presented as proof of concept.