My thesis covers the planning and production process of a communication interface board designed for automotive industry-related measurements. The function of this interface does the transformation of information generated by a TTL physical layer into a signal on a physical layer corresponding the PSI5 automotive industry standards.
The PSI5 is a safety-critical, two-way communication standard commonly used by the automotive industry. It has an important task in the communication with sensors. The sensors measure air pressure, acceleration, rotation and temperature which is necessary information for the airbag systems.
The PSI5 standard defines a two-wire bidirectional communication, where during the communication the Electronic Control Unit is responsible to provide the power supply of the sensors.
In synchronous mode, the ECU sends synchronization signals via the power supply superimposed synchronization pulses, or give instructions to the sensor(s). Instruction signals are transmitted either by omitting the synchronization pulses or varying the length of the synchronization pulses.
The sensor can send the data to the ECU by modulating its power consumption via Manchester coding.
For the testing and measuring of these sensors a special device is required. It should generate ECU side signals, such as securing supply voltage, generate synchronizing pulses in synchronous mode, modulate synchronous pulses in the case of bi-directional communication, and interpret the sensors signals.
Although such a tool exists, but there is no device that can produce the current modulated signal on the sensor side, and is capable of detecting the synchronizing pulses, and checking the supply voltage coming from the ECU by this way realizing an arbitrary sensor at communication level.
To solve this problem, a system should be built, that is capable of emulating a sensor. Emulators can normally only communicate on TTL level signals.
My task was to physically map the sensor signals from this asymmetrical bi-directional communication from TTL signals to PSI5 standards.
The circuit I designed converts the ECU generated synchronization pulses to the TTL signal level and sends a signal arriving at the TTL signal as the signal of the PSI5 communication.
My following thesis covers the creation of the basic concept, its simulation, and based on the results the design, tuning and measurement of the circuit.