Far beyond Tesla: Analysis of the next-generation BMW electronic architecture

BMW's new generation of electronic architecture began to be designed in early 2016 and officially went into mass production in September 2018. It makes extensive use of Ethernet and domain controllers , and its design is far more advanced than the Tesla  Model 3, which was designed later.

The above picture shows the electronic architecture of BMW's new generation vehicle. KOMBI: Instrument. DCS: Driver Status Monitoring System. TCB: T-box. RAM: Audio Receiver System. Booster: Premium Sound System. RSE: Rear Seat Entertainment System. TRSVC: 360 Surround View. KAFAS: Front Three-Eye ADAS System. FRS: Front Radar. FRSF: Front Long-Range Radar. SAS: ADAS Domain Controller. SRSNVR: Front Right Radar. SRSNVL: Front Left Radar. HRSNL: Rear Left Radar. HRSNR: Rear Right Radar. PMA: Automatic Parking System. DSC/VIP: Brake Actuator. WCA: Wireless Charging. ZGM: Central Gateway. ACSM: Passive Safety Controller. FLEL: Front Left Lamp. FLER: Front Right Lamp. EGS: Electronic Transmission Control.

Gray represents Ethernet nodes, dark red represents Flexray nodes, and orange represents CAN nodes. The CAN bus is further divided into local CAN, K-CAN, and PT-CAN. K is the abbreviation of Kommunikation, which means communication in German, similar to Communication in English. PT is the abbreviation of PowerTratin. K-CAN5 connects FBD (remote control reception), wireless charging, and NFC. K-CAN4 connects FZD (roof function center, including gesture recognition system based on TOF camera), Headunit, TCB, and RAM. K-CAN2 is mainly for seats and trailer systems. K-CAN6 is for headlight control. Local CAN is mainly connected between millimeter-wave radar and controller. PT-CAN is divided into two routes, one is from instrument to BDC, DME, and engine management system to BDC. The other route is mainly for gearbox and NVE night vision system.

BMW's new generation system has three domain controllers, namely:

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• BDC, body domain controller;

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• Headunit is MGU, cockpit domain controller;

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• SAS (optional equipment), namely ADAS domain controller.

The core of each domain controller is an Ethernet switch and gateway. In the 360-degree view, that is, TRSVC, there is also an Ethernet switch. The Ethernet switch used by BMW is provided by Broadcom, and the model may be BCM89501 (2011) or BCM89531 (second generation, 2015), which specifically supports the 802.1AS protocol, that is, the precise time synchronization protocol, which is also a key part of the TSN network. 

Tesla, on the other hand, uses the EAVB system for in-car entertainment systems (started in 2005, EAVB was cancelled in November 2012 and replaced with TSN), using the EAVB switch 88E6321, without 802.1AS. This is a special EAVB series product for automotive audio and video entertainment applications in the Marvell LINK-STREET series. The Flexray bus used in the BMW chassis system has security backup and time triggering functions, and its security is far superior to the CAN bus (no backup, event triggering, low reliability) used by Tesla.

The above picture shows the new generation of BMW cockpit electronic architecture, namely the fifth generation MGU (Media Graphics Unit), and its Headunit, BMW internal code name HU-H3. Taking the European and American markets as an example, the early BMW central control or Infotainment separated navigation from basic functions. The 1, 2, 3, 4 series and X1, X2, X3, X4 series are still the same, and the entry-level models do not have navigation. The high-end 5, 6, 7 and X5, X6, X7 and 8 series are combined into one. BMW has introduced the operating system idrive, referred to as ID, since 2001.

The fifth-generation MGU has undergone major changes, abandoning the QNX operating system and switching to the LINUX system redeveloped by BMW, namely GENIVI+LINUX. GENIVI is an alliance dedicated to using LINUX and other open source software in automotive cockpit electronics. Major OEM members include BMW, Hyundai, Honda, Daimler, Nissan, PSA and SAIC. Major Tier1s include Alpine, Aptiv, Clarion (Faurecia), Denso, Hyundai Mobis, LG and Bosch. Chip manufacturers include NXP, Renesas, NVIDIA, MediaTek, ADI, ARM and Telechips. Middleware and software manufacturers include Neusoft, Wind River, QT, KPIT and Green Mountain. MGU is also the first time that BMW uses the LINUX system. MGU was first used in the top configuration of the 3 Series in 2019, and then in the entire 7 Series, Z4, X5 and X7 and 8 Series. It will be fully introduced in the future.

MGU abandoned the MOST bus and switched to OABR (OPEN Alliance BroadR-Reach) in-vehicle Ethernet. The alliance was founded in 2011 by BMW, Hyundai, NXP, Freescale, HARMAN, STMicroelectronics, and Broadcom. OPEN is the abbreviation of One Pair Ethernet Network. OABR has been standardized by IEEE and named 100BASE-T1. The name of the traditional 100M Ethernet is 100BASE-TX, and the two are very different in the physical layer. The most significant difference between the two is that 100BASE-T1 uses a pair of twisted pairs in the physical connection to achieve full-duplex information transmission, while 100BASE-TX uses two pairs of twisted pairs to achieve full-duplex, one pair for receiving and the other for sending. 100BASE-T1 uses the so-called echo cancellation technology to achieve full-duplex communication on a pair of twisted pairs.

The general process of echo cancellation technology is as follows: the node as the sender loads the differential voltage to be sent onto the twisted pair, and the node as the receiver subtracts the voltage sent by itself from the total voltage on the twisted pair. The result of the subtraction is the voltage sent by the sending node. BroadR-Reach is a special trademark of Broadcom for its own in-vehicle Ethernet products. Therefore, it can be considered that 100BASE-T1=OABR=BroadR-Reach. However, the disadvantage is that OABR mainly supports point-to-point communication, bidirectional 100MBits, and still uses traditional Ethernet in OBD2. In contrast, Tesla uses the EAVB system for in-vehicle entertainment systems and uses the EAVB switch 88E6321, which is Marvell's LINK-STREET series product for SOHO offices.

The above picture shows the framework of the entire cockpit system

(1 is Central Information Display, CID, 2 is HU-H3, 3 is user interface, 4 is application software, 5 is connection system)

HU-H3 connects to 4 Ethernets, namely the instrument, RAM, BDC and TCB.

There is a USB power supply interface on the side and rear of HU-H3, and there are 8 main interfaces on the rear, as shown in the figure above. 1 is the Bluetooth air interface, 2 is the WLAN air interface, 3 is the USB Type-A interface, 4 is the USB Type-C interface, 5 is the USB interface for external CD, 6 is the APIX display interface, connected to the central control screen (Central Information Display, CID), 7 is the CAN connection, and 8 is the Ethernet interface. In some countries, such as Eastern Europe or Russia, MGU adopts a built-in CD player design (the Chinese have long eliminated CD players, and Europeans, especially Russians, still use CDs more), but there is no navigation function. Because it was designed in early 2016, it still uses a mechanical hard disk as the main storage. The hard disk capacity is 320GB, of which navigation occupies 160GB, entertainment occupies 34GB, and networked music occupies 16GB, and the available space is 34GB.

The above picture shows the third generation of BMW, namely NBT architecture. Currently, Texas Instruments' DRA44X series chips (i.e. J6) are no longer available for public sale. NBT EVO may have switched to the DRA71x series. There is also a missing graphics chip in the picture, which is Nvidia's EMP9. Entry-level products use FPGA to replace Texas Instruments' DRA44X. BMW continues to use this architecture design. Intel's ATOM E660 (NBT uses E660, MGU uses a confidential model J626C159, which is speculated to be Intel A3930, and Tesla uses A3950) is mainly responsible for the operating system and networking services. J6 is responsible for navigation and peripherals.

The above picture shows RAM, 1 is CAN connection, 2 is Ethernet connection, 3 is SDRAS air interface connection, and 4 is AM/FM radio air interface. On the MGU, this dual-processor design is continued, but there are also big differences. BMW puts audio reception and navigation in a separate box from RAM, physically separated. The HU-H3 box is almost unchanged from the NBT, still using Intel's Atom and Renesas' RH850 MCU. This design retains the original design results and increases flexibility. It can be said to be quite advanced, but the hardware cost has increased significantly. The HU-H3 also includes WLAN and Bluetooth, using Broadcom's Bluetooth and WLAN two-in-one module 91UWM255.

10 is HU-H3, 6 is RAM, 8 is Booster, 3 is the driver side microphone, and 5 is the passenger side microphone.

BMW pays special attention to the sound system, which is divided into three versions. The standard version (SA676) has a power of 205 watts, including 3 tweeters, 5 midranges, and 2 bass units. The mid-level version (SA688) is Harman Kardon surround sound, with a power of 464 watts, including 5 tweeters, 5 midranges, and 2 bass units. The advanced version (SA6F1) is Bowers & Wilkins diamond surround sound, with a power of 1200 watts, including 7 tweeters, 7 midranges, and 2 bass units. The navigation board in RAM is complex in design and uses Renesas's R-CAR H3 as the main chip.

The above picture shows the internal framework of R-CAR H3

BMW is using Ethernet crazily at all costs, probably hoping to simplify the wiring harness, reduce costs on the wiring harness, and reduce the weight of the wiring harness. According to the wiring diagram, the R-CAR H3 may use two Ethernet outputs, one of which is audio to Ethernet output to the Booster, which is a bit of a waste of resources, and the audio real-time and bandwidth requirements are not high. The other one is the conversion of video output to Ethernet output. H3 has 4 video outputs, including one analog video, one LVDS and two HDMI. MGU uses three, which are probably CID, instrument and HUD. RAM needs to convert all three channels to Ethernet format. It is easy to convert HDMI to Ethernet, that is, IP format, and LVDS is a little troublesome, and then add a small Ethernet switch.