Analyzing CXPI interfaces for automotive applications

September 29, 2016 // By Graham Prophet
Rohde & Schwarz has expanded the functions on its R&S RTE and R&S RTO digital oscilloscopes to include a triggering and decoding option for the new CXPI protocol. This newly developed automotive bus is a cost-effective alternative to the LIN protocol. CXPI interfaces can now be tested early in the design phase.

The R&S RTx-K76 CXPI serial triggering and decoding option allows users to analyze the clock extension peripheral interface (CXPI) communications bus with R&S RTE and R&S RTO oscilloscopes. Users can decode all protocol details and isolate anomalies by triggering on the corresponding details. This significantly accelerates design verification and implementation of CXPI interfaces.


CXPI was standardized in 2015 under SAE J3076 as a communications bus for diverse automotive applications. The bus uses pulse width modulation to transmit data over a single wire at 20 kbit/sec. The characters used are based on UART.


When debugging CXPI interfaces during development, users can trigger on conditions such as start of frame, frame ID, data values and various error conditions. The instrument's powerful search and navigation functions make it easy to detect relevant events in the CXPI data stream. The oscilloscope displays decoded telegrams as colour-coded bus signals in a waveform diagram or as a table. As a result, developers can verify the quality of their products early during development.


The R&S RTE and R&S RTO let users simultaneously decode up to four serial buses from analogue or logic signals. The oscilloscopes also deliver the fastest eye diagram mask tests using the standard mask test functionality.


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