This article presents an approach to simulating hybrid systems. We show how a discrete controller that controls a continuous environment can be co-simulated with the environment (plant) using C-code generated automatically from mathematical models. This approach uses Signal with Simulink to model complex hybrid systems. The choices are motivated by the fact that Signal is a powerful tool for modelling complex discrete behaviours and Simulink is well-suited to deal with continuous dynamics. In particular, progress in formal analysis of Signal programs and the common availability of the Simulink tool makes these an interesting choice for combination. We present various alternatives for implementing communication between the underlying sub-models. Finally, we present interesting scenarios in the co-simulation of a discrete controller with its environment: a non-linear siphon pump originally designed by the Swedish engineer Christofer Polhem in 1697.