A PC BASED, INTELLIGENT AND DUAL PURPOSE TEST RIG, FOR THE FUNCTIONAL EVALUATION OF AN EMBEDDED SYSTEM

摘要

A PC based Test Rig, to functionally qualify the Electronic Control Unit (ECU), a microcontroller based embedded system, is designed and developed. The Test Rig consists of a PC with a DAC Card, a DIO Card, a host software on the PC, a qualifying software in the ECU and an interface hardware, with level translators, relays, resistor loads and signal paths. The functions of the ECU are to control, monitor and coordinate the activities related to the selection of the appropriate source of breathing gas, for the pilot, to overcome the physiological problems, which arise due to hypoxia, at high altitudes. The Test Rig, in turn, checks the ECU for its (i) efficacy and the accuracy of the timing, in driving the solenoids and a heater coil, simulated by the resistor loads, especially in driving the solenoids of the Molecular Sieve Oxygen Concentrator System (MSGCS), which generates enriched oxygen, to meet the physiological requirements of the pilot at different altitudes, (ii) accuracy of the signal conditioning, in response to the analog inputs from the sensors, simulated by the output signals from the DAC Card, (iii) efficacy, (a) in determining the failure conditions of the loads and the sensors, through feed back circuits, with the failures being simulated by opening the loads/DAC cable and (b) to communicate through two channels of RS422 based communication, simulated by level translators, as per a predetermined protocol and (iv) Response to some special switches, simulated by discrete inputs. The Test Rig software, issues appropriate commands, either to (i) the DAC Card, to send analog signals to the ECU or (ii) the DIO Card, to send/receive discrete signals to/from the ECU or (iii) the RS232 port to communicate with the ECU The response of the ECU is either captured as discrete input signals, or received as message packets over the communication channels, by the Test Rig and the same is used in ascertaining the functionality of the ECU hardware. This makes the Test Rig, 'intelligent' in nature. The same setup has also been used to carry out the black box tests of the application software, which has been developed for the ECU This makes the Test Rig, 'dual purpose', in nature. The issues related to such a hardware and software design, are discussed, in this paper.