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Improving PSI5 silicon validation setup

06 Nov 2015  | Jalaj Jain, Paras Arora, Ramesh Sangolli

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Peripheral Sensor Interface 5 (PSI5) is an interface for automotive sensor applications. It is used to connect peripheral sensors to electronic control units (ECUs) in automotive electronics. The main features of PSI5 are:

 • Two-wire current interface
 • Manchester coded digital data transmission
 • High data transmission speed of 125kbps and 189kbps
 • Wide range of sensor supply current
 • Variable data word length (10 to 28 bit with one bit granularity)
 • Asynchronous and synchronous operation and different bus modes
 • Bidirectional communication

The PSI5 master supplies a pre-regulated voltage to the slave sensor and modulates the supply voltage in the positive direction to provide synchronisation of the sensor data. Data transmissions from the sensor to the master are accomplished via modulation of the current on the power supply line.

Figure 1: Voltage and current modulation in PSI5.

Validation of PSI5 is a complex task as both power supply and data are present on a single line. The master sends the synchronisation pulses on power line (voltage modulation) and slaves respond by sending information using supply current modulation. Both analogue and digital information is present in modulated current waveform.

Presently PSI5 Simulyzers are used to validate PSI5 interface in the industry. These simulyzers consist of a hardware part, which communicates with the ECU or the sensor to be validated, and the GUI to control the hardware part. The simulyzer can be set to operate as an ECU for the validation of a sensor, or as a sensor for the validation of an ECU, or as an analyser to analyse the data and signals.

When validating a sensor, a simulyzer provides supply and sync pulses to the sensor. The response from the sensor can be analysed by viewing the signals in the scope within the GUI or by comparing the recorded data with the expected data. The response format that is expected from the sensor is checked by the simulyzer and the CRC checks are also carried out. Thus, most of the tests can be conducted by using the PSI5 Simulyzer.

There are a few limitations of PSI5 simulyzers due to which 100% test coverage cannot be achieved. These limitations are:

 • Power supply – Some sensors work at as low as 4V but PSI5 simulyzers available in market do not work at 4V
 • Using PSI5 interface and DSI3 interface in parallel – Some sensors support checking functionality of PSI5 mode when in DSI3 mode. This cannot be done using simulyzers these are different for PSI5 and DSI3 modes
 • Timing control – Simulyzers can control the timing parameters but only before starting the communication. Once communication starts, changing the parameters is not possible. Thus, tests which include generation of missing sync pulses and changing sync pulse parameters on the fly are not possible.
 • Supply error scenarios – As parameters cannot be changed while ECU and sensor are communicating, generation of supply under-voltage scenarios is not possible.

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