CXPI automotive serial bus analysis.

CXPI serial bus analysis has been added to the range of options available on Yokogawa’s DLM2000 and DLM4000 Series mixed signal oscilloscopes.

CXPI – Clock Extension Peripheral Interface – is a new automotive serial bus interface that is designed to provide an optimised solution in applications previously served by the established CAN and LIN bus systems, which until now have been the main interfaces used for in-vehicle communications. In particular, as more sensors and human-machine interfaces are used in vehicles and controls become ever more sophisticated, the new bus helps to minimise system power consumption through electronic control as well as reducing vehicle weight by using lighter components, especially in wiring harnesses.

With LIN, it is difficult to achieve sufficient reliability and communication response when multiplexing in HMI applications. CAN is better for reliability and communication response, but the cost is higher than LIN.

The CXPI protocol, on the other hand, is a low-speed low-cost communication protocol that is capable of reducing wire counts to simple devices like switches and sensors.
CXPI was standardised 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/s. The characters used are based on UART.

CXPI has the CSMA/CR system (event initiate system) built into the polling system of LIN, which provides higher response time and scalability, and significantly reduces HMI and development costs. It has reduced the number of the parts needed for the clock side of the design because a data and a clock signal can transmit at the same time via PWM.

When equipped with the CXPI option, the DLM Series oscilloscopes will decode and display CXPI frames in real time, produce a list display of the decode results, and allow highlighting of points on the list for display in a zoom window. After the acquisition, dedicated parts of the display can be searched for a number of specified conditions.
An auto setup feature can be used to analyse the input signals, set the time and voltage axes automatically along with various trigger settings such as threshold levels, bit rates and trigger type, and then display the decoded result.

Yokogawa’s DLM2000 and DLM4000 mixed-signal oscilloscopes combine a fast update rate with exceptionally long memory plus a combination of flexible analogue and digital outputs that make them ideally suited to a range of measurement and analysis tasks in the electronics, automotive and mechatronics sectors.

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