Fault injection simulation on embedded software is typically captured using a high-level fault model that expresses fault behavior in terms of programmer-observable quantities. These fault models hide the true sensitivity of the underlying processor hardware to fault injection, and they are unable to correctly capture fault effects in the programmer-invisible part of the processor microarchitecture. We present SimpliFI, a simulation methodology to test fault attacks on embedded software using a hardware simulation of the processor running the software. We explain the purpose and advantage of SimpliFI, describe automation of the simulation framework, and apply SimpliFI on a BRISC-V embedded processor running an AES application.