This protocol covers the application layer in the OSI model of computer networking. KWP also covers the session layer in the OSI model, in terms of starting, maintaining and terminating a communications session. One underlying physical layer used for KWP is identical to ISO , with bidirectional serial communication on a single line called the K-line. In addition, there is an optional L-line for wakeup. The data rate is between 1.
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The demand for a more accurate, standard and efficient fault detection in vehicle diagnostics, has led to breakthrough innovations and developments.
Earlier, there were flash codes wherein technicians had to look for flashes and convert them to codes or sometimes the technician had to physically remove vehicle components, disconnect wires for fault detection.
The increasing complexity of vehicle systems over the time mandated the need for diagnostics standards to efficiently track their scope and relevance. To cater to this need of the hour, various vehicle diagnostic protocols were conceptualized and developed. ISO and SAE Society of Automotive Engineers introduced various diagnostic protocols and standards, designed to cater to the different types of automotive ECU systems and diagnostics specifications from the vehicle manufacturers.
Image credit: nextews. Let us have a look at two protocols in detail:. The KWP protocol uses a physical layer, identical to ISO , for bidirectional serial communication over K-line with the controller.
The average data rate of KWP is between 1. The maximum size of message supported within UDS is up to 8 bytes. UDS as a diagnostic protocol was developed to unify all the diagnostics standards that existed previously and to come up with a single valid set of diagnostic services for the automotive ECUs. This has ensured that integration of the UDS protocol stack reduces the additional costs for the development of diagnostic communication applications.
While, UDS protocol can be seen as a superset of the KWP , since it is derived from the latter, a comparison of both as the diagnostic protocols gives out some interesting facts:. KWP is highly preferred where the vehicles are based on legacy systems such as K-line. Otherwise, these days UDS protocol is the go to standard for vehicle diagnostics. Transfer of Key Measurement Values : Both the diagnostic protocol facilitate exchange of request and command messages from the test equipment to the automotive ECU; and key measurement values data in response from the vehicle ECU.
But, there is a key difference between the two protocols in the way these measurement values are exchanged between the tester and ECU:.
This means increased efficiency of data exchange. Diagnostic Communication between Test equipment and vehicle ECU : The exchange of messages between testing device and the vehicle ECU forms the basis of the diagnostic system. The natures of request and response messages and data transfer interval between them form an important factor in vehicle diagnostics.
KWP favors symmetrical communication sequence where the number of request and response messages between the testing device and server are symmetrical. On the other hand, UDS is based on an event driven and periodic communication sequence. This means, the number of request and response messages can be different.
Moreover, in a periodic communication sequence based on UDS standard, the test equipment sends periodic requests for updated information from automotive ECUs.
This helps in closely monitoring vehicle condition in regular intervals. The vehicle ECU may respond to the periodic request with one or several data record values. Thus UDS offers more detailed information related to the fault through periodic update.
KWP uses following services for error memory management:. With the help of the additional sub functions, UDS enables the tester to collect more diagnostic information. This is useful in the modern automotive industry where the complexity of design and number of components in the vehicle are increasing. Protocol Dependency KWP functionalities for measurement value transfer and error memory management were improved for UDS standards.
Is based on event-driven and periodic services. Hence number of requests and response between the tester and the ECU can vary. It is independent of the vehicle bus systems. KWP and UDS are both used in modern automobiles for efficient and accurate diagnosis of vehicle health and faults. Over the time, UDS protocol owing to its robustness and a broader service spectrum is expected to be the future of automobile diagnostics.
UDS protocol is defined by redundancy of functionalities whereby various UDS services can be used to execute a certain diagnostic function.
Thus, UDS as a diagnostic protocol paves way for added services and functionalities. But it also calls for additional requirement for ECU memory along with extra development costs. Thus it is important to ponder over certain questions, before deciding on the implementation of UDS services for your application, listed as:.
If you take these questions into account, you will be able to successfully implement UDS within your automotive application without any unnecessary development costs or efforts.
Talk to our Automotive experts to know how you can seamlessly implement and integrate UDS software stack according to your automotive use-case. Enjoy the experience, without worrying about your data! Great, thanks! Skip to content Skip to primary sidebar.
Work with us People at Embitel Life at Embitel. Evolution of Vehicle Diagnostics: Earlier, there were flash codes wherein technicians had to look for flashes and convert them to codes or sometimes the technician had to physically remove vehicle components, disconnect wires for fault detection. Thus it is important to ponder over certain questions, before deciding on the implementation of UDS services for your application, listed as: What services are necessary for you?
What sub functions and parameters are important to be considered for UDS implementations? What data identifier and parameters should be focused on? Contact Us. All Rights Reserved. KWP functionalities for measurement value transfer and error memory management were improved for UDS standards.
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