Abstract
Power-train architecture using low cost ECUs consists of a master EMS ECU and a few other auxiliary ECUs for auxiliary-add on functions like EGR controller, fan controller, glow-plug controller. Some of the ECUs need to be added to address upcoming market requirements like “start-stop feature” for micro-hybrid applications.
All these “add-on”/slave ECUs need to share sensor information like engine rpm, coolant temperature etc. Needless to say, these low cost vehicle options cannot accommodate costly networking options like CAN. Instead the master EMS provides these signals as Pulse Width Modulated buffered “Fan-outs” which are sensed by the auxiliary ECUs.
This paper describes a novel low cost method for reading such PWM signals using unused serial port of the slave ECUs. Unlike conventional approach of using precious on-chip timer resources (which are normally tied-up in counting and timing application), this method takes use of unused communication resources of the low cost micro-controller used on slave ECUs. It also relieves the CPU from the burden of pulse-width measurement in real time. At the end the paper highlights wider potential of the concept in other automotive applications where timemeasurement needs to be carried out in efficient manner.
KEYWORDS: Power train, Electronic control units (ECU), Pulse width modulation (PWM), Synchronous serial communication, Duty Cycle.