Based on our previous work on the development of a Wireless Sensor Network (WSN) simulation platform, we present here its ability to run simulations on heterogeneous nodes. This platform allows system-level simulations with low level accurate models, with graphical inputs and outputs to easily simulate such distributed systems. In the testbed we consider, the well known IEEE 802.15.4 standard is used, and different microcontrollers units (MCU) and radiofrequency transceivers compose the heterogeneous nodes. It is also possible to simulate complex networks or interacting networks; that is a more realistic case, as more and more hardware devices exist and standards permit their interoperability. This simulation platform can be used to explore design space in order to find the hardware devices and IEEE 802.15.4 algorithm that best fit a given application. Packet Delivery Rate (PDR) and packet latency can be evaluated, as other network simulators do. Energy consumption of sensor nodes is detailed with a very fine granularity: partitioning over and into hardware devices that compose the node is studied.