Developing Distributed Hard-Real Time Software Systems Using FPGAs and Soft Cores

Hard real-time systems guarantee by design that no deadline is ever missed. In a distributed environment such as particle accelerators, there is often the extra requirement of having diverse real-time systems synchronize to each other. Implementations on top of general-purpose multi-tasking operating systems such as Linux generally suffer from lack of full control of the platform. On the other hand, solutions based on logic inside FPGAs can result in long development cycles. A mid-way approach is presented which allows fast software development yet guarantees full control of the timing of the execution. The solution involves using soft cores inside FPGAs, running single tasks without interrupts and without an operating system underneath. Two CERN developments are presented, both based on a unique free and open source HDL core comprising a parameterizable number of CPUs, logic to synchronize them and message queues to communicate with the local host and with remote systems. This development environment is being offered as a service to fill the gap between Linux-based solutions and full-hardware implementations.