The scan interface (SIF) of the MSP430F42x family of microcontrollers provides an innovative, low-power method to measure rotation that can be used with a variety of sensor types. Many sensor configurations generate a quadrature signalling sequence, but some do not. The SIF can accommodate a variety of input signals – not just quadrature.
This application report describes implementation of a rotation detector that uses a pair of giant magneto-resistive (GMR) sensors, which can detect magnetic fields. The sensors are positioned such that they do not use a quadrature signalling sequence, and this provides an opportunity to discuss how the SIF can be configured for non-quadrature situations. Techniques for debugging SIF applications are discussed, and a tool is provided for designing non-quadrature processing state machines.