High-speed Measurements for Electric and Hybrid Vehicles New Measurement Concepts Enable High Data Rates and Frequent Sampling Times In the development of electric and hybrid vehicles, in particular, the requirements for instrumentation used to measure internal ECU signals are very high. Nonetheless, measurement data rates of up to 30 Mbyte/s and the necessary sampling rates of 100 kHz can be achieved with the latest generations of microcontrollers and an intelligent measuring instrumen- tation solution. The ECU’s CPU is not loaded here. The drives of electric or hybrid vehicles are generally con- pins and the POD is 10 cm. Communication between the trolled by pulse-width modulation (PWM) signals. The ad- measuring instrumentation module and the test PC is over vantage of PWM technology is that it incurs very low power XCP on Ethernet in accordance with the MCD-1 XCP stan- losses at power switches, because they only need to be dard from ASAM. The physical connection is made by a operated in two operating states: fully conducting or fully standard CAT-5 Ethernet cable. Essentially, two different blocking. The frequency of the PMW signals typically lies in measurement methods are distinguished: the “RAM copy the 10 – 20 kHz range, and in exceptional cases up to method” and the “data trace method.” They are presented 100 kHz. Maximum sampling rates of only 1 kHz are achiev- in this article, together with their advantages and disad- able for internal ECU signals when XCP – a widely used vantages, based on current microcontrollers and new standardized measurement and calibration protocol for ve- microcontrollers that will be available soon. The different hicle development – is used together with communication data trace methods refer to two types of 32-bit microcon- over the CAN or FlexRay bus system. PMW signals cannot trollers that are primarily used in powertrain ECUs and be acquired in this method. their successors: Freescale PowerPC (primary market: That is why the debug and data trace interfaces are used USA) and Infineon TriCore (primary market: Europe). for fast access to ECU variables. These interfaces can vary significantly depending on the type of microcontroller that RAM Copy Method is implemented. The measurement hardware is interfaced The RAM copy method is a generic method, and can be to the ECU over a “Plug-On Device” (POD). The maximum used for current and future generations of 32-bit microcon- allowable distance between the microcontroller’s debug trollers from various manufacturers. For the Infineon 1 TriCore or XC2000, access is via the Device Access Port where new changes are saved in a First In, First Out (FIFO) (DAP) interface; for the PowerPC devices from Freescale or buffer in RAM. The measurement is initiated by one of up to V850 E2 processors from Renesas, access is via the Nexus 256 different software triggers, and the contents of the Class 2+ interface. In this method, the ECU software initi- mirrored RAM are “frozen”. Based on the measurement ates a RAM copy function according to the cycle time of the configuration, the signals are read out from the mirrored various ECU tasks. The measurement signals must be RAM in the base module for measurement data and are preconfigured over XCP on Ethernet. The mapping of signal sent to the measurement and calibration tool over XCP on names and RAM addresses is described in an A2L file (ASAM Ethernet (Figure 2). standardized ECU description file for signal-oriented RAM Advantages of the Nexus Class 3 solution: accesses). Once all measurement signals have been copied, > The maximum measurement data rate of 30 Mbyte/s is the signals are transmitted to the base module for mea- a factor of 30 times larger than with Nexus Class 2+ and surement data according to the existing debug interfaces 600 times larger than with XCP on CAN. (Figure 1). This concept is referred to as “Online Data > The CPU is typically not loaded by the measurement. Acquisition” (OLDA). > All PWM drive signals can be measured at the 100 kHz Compared to CAN, the measurement data rate and sam- sampling rate without any problems. pling rate are improved by a factor of 20, i.e. 0.5 to 1 Mbyte/s of measurement data can be acquired with a sampling rate The disadvantage of this solution lies in the fact that signif- of 10 – 20 kHz. The copying operation loads the CPU approx. icant effort is involved in connecting the POD with its 25 4% at 1 Mbyte/s. pins to the microcontroller, and it must process a very large raw data stream of 100 Mbyte/s. Data Trace Concept for Nexus Class 3 – Current Freescale PowerPC Data Trace Concept for Next Generation Microcontrollers Most devices of the current Freescale PowerPC series sup- The main disadvantage of the Nexus Class 3 solution will be port the data trace method of Nexus Class 3. In this case, the eliminated in next generation microcontrollers, because the developer configures one or two monitoring windows with pin count has been reduced from 25 to 5. However, the a maximum total size of 512 kByte in the ECU RAM. Any measurement data rate and sampling rate will remain at changes within these monitoring windows are transmitted the same unchanged high level. This data trace solution will to the POD via Nexus Class 3 without any additional CPU also be supported by future processors from the Infineon load. Transmission rates for raw data of up to 100 MByte/s and Freescale companies. The raw data stream von are possible over the High Speed Serial Link cable. The ad- 100 Mbyte/s must still be processed. vantage of this concept is that the base module for mea- surement data always contains a consistent mirrored RAM Data Trace Concept for the Current Infineon TriCore of the ECU’s RAM. An ECU software trigger interrupts the A concept comparable to Nexus Class 3 may also be used data flow within the measurement data base module, for DAP. This involves reserving a 256 kByte memory range Figure 1: Data flow concept for measurement signals by the RAM copy method and Nexus Class 2+ interface 2 Figure 2: Data flow concept of measurement signals by the data trace concept and Nexus Class 3 interface of the ED-RAM (Emulation Device RAM) for measurement One advantage lies in its higher raw data transmission data acquisition. In contrast to the 100 MByte/s of the rate, which is now 20 MByte/s in contrast to the previous Nexus Class 3 concept, the trace transmission rate for raw 5 MByte/s. This is attained by the higher frequency of data must be limited to 5 MByte/s; just 4 pins suffice in- 160 MHz at the DAP interface instead of the previous stead of 25 pins. A maximum of four RAM monitoring win- 80 MHz and by a new type of three-line concept, which dows may be configured. They must be configured so that permits parallel transmission on two lines. there is no overrun of the trace data. Generally, this per- The greatest improvement to the DAP2 interface is that it mits monitoring of just 10–20 kByte of memory instead of now lets users set up hardware-based data trace filters 512 kByte and measurement of signals in this memory with extremely fine granularity. This significantly reduces without processor loading. Signals outside of these trace the transmission of unnecessary data trace information monitored memory areas can be measured by the RAM from the microcontroller to the POD. Despite the maxi- copy method. mum measurement data rate of 10 Mbyte/s, it is only nec- Advantages of the Infineon DAP data trace solution: essary to process 15 instead of 100 Mbyte/s of raw data > The maximum measurement data rate of 3 Mbyte/s is a (Figure 3). Due to the considerably reduced requirements factor of 3 larger than in the RAM copy method. for processing the measurement data, cost-optimized > The microcontroller is not loaded by the measurement. measuring instrumentation can be used for DAP2. > All known PWM drive signals can be measured at a 100 kHz sampling rate without any problems. Summary Many aspects of modern drive concepts for vehicles with Data Trace Concept for Future Infineon controllers pure or hybrid electric motors make it necessary to develop In the next generation of microcontrollers, Infineon is also new strategies for measurement data acquisition. Existing offering the latest generation Device Access Port (DAP). measuring instrumentation concepts for internal ECU sig- Figure 3: In the data trace concept, fine grain filters reduce the raw data stream to 15 Mbyte/s over the DAP2 interface. 3 High-speed Measurements for Electric and Hybrid Vehicles nals often reach their limits in terms of data rate or sam- pling rate. The sampling rates of up to 100 kHz that are necessary for electric drive systems can be implemented for existing and future microcontrollers using the VX1000 measurement and calibration hardware from Vector. Over the course of this year, new controller generations will be available from Freescale and Infineon, which can perform their tasks with a data trace that requires significantly fewer connection pins. In combination with the high-speed VX1131 measurement module from Vector – which will be available in the second half of 2012 – they will enable mea- surement data rates of 30 Mbyte/s without CPU loading. In the case of Infineon, DAP2 with finely granulated signal filters in the microcontroller make it possible to reduce the raw data stream from 100 to 15 Mbyte/s, which permits the use of very cost-efficient measurement hardware to achieve high data rates.