Innovative digital bus architecture reduces audio system costs

Automakers are committed to making their next generation cars safer, smarter and more fuel-efficient than before. For this reason, more ECUs (Electronic Control Units) need to be deployed in cars to realize smart radio connections, active road noise reduction (RNC), personal zone zone (PAZ), in-vehicle communication (ICC) and autonomous driving Such as new features and functions, this will lead to an increase in the number of electronic systems, and more and more complex road noise active noise reduction. As the number of ECUs continues to increase, the weight and cost of cables required to connect various ECUs also increase. The increased weight will in turn reduce the fuel efficiency of the car, which makes car manufacturers very distressed.

Automakers are committed to making their next generation cars safer, smarter and more fuel-efficient than before. For this reason, more ECUs (Electronic Control Units) need to be deployed in cars to realize smart radio connections, active road noise reduction (RNC), personal zone zone (PAZ), in-vehicle communication (ICC) and autonomous driving Such as new features and functions, this will lead to an increase in the number of electronic systems, and more and more complex road noise active noise reduction. As the number of ECUs continues to increase, the weight and cost of cables required to connect various ECUs also increase. The increased weight will in turn reduce the fuel efficiency of the car, which makes car manufacturers very distressed.

Automakers must strike a balance between providing advanced, feature-rich infotainment systems and meeting government-promulgated fuel efficiency standards. Reducing the weight of existing cables can greatly improve fuel efficiency.

status quo

Traditional car audio ECUs are generally connected through a separate analog cable or an existing digital bus architecture, both of which have limitations, low efficiency, and unnecessary costs. Car audio systems that use analog transmission lines require special and expensive shielded cables to transmit multi-channel audio signals. In today’s advanced audio systems that support multi-channel (5.1 or 7.1) Dolby or DTS decoding, the number of cables required is rapidly increasing. Moreover, additional analog-to-digital converters (ADC) and digital-to-analog converters (DAC) will not only increase the total system cost, but may also degrade some audio performance.

Digital bus standards such as MOST® or Ethernet EAVB have been widely adopted in contemporary infotainment systems because these standards can greatly simplify the connection complexity of analog implementations. However, although MOST and Ethernet EAVB can improve performance and flexibility,

But it is necessary to add a high-priced microcontroller to implement the relevant software protocol stack, thereby increasing the system cost. In addition, these digital bus architectures are inherently uncertain about the delay between nodes. For applications that are susceptible to delays such as ANC/RNC and ICC, the fundamental flaws in the existing digital bus architecture are unacceptable.

Introduction to car audio bus

Car Audio Bus™ (or A2B™) is an innovative, application-oriented technology of ADI. Facts have proved that this technology can reduce the overall cable weight by up to 75%, and it can also provide high-fidelity digital audio. Car audio bus (A2B) Optimized for audio applications, it can provide excellent audio quality compared to analog audio buses, and the total system cost is much lower than the existing digital bus standards. In short, A2B is a high-bandwidth (50 Mbps) digital bus, which can be used over a very long distance (the distance between nodes is up to 15 m, and the length of the entire daisy chain exceeds 40 m).2S audio, I2C Control data, clock, and power supply are transmitted together.

Basic characteristics of car audio bus

Product-AD2427W and AD2426W together form the latest enhanced A2B transceiver series, and pin compatible. This latest product supports the use of a single master daisy chain, and up to 10 slave nodes, and the first generation A2Compared with product B, its performance has increased by 20% (see Figure 1). With this daisy chain capability, A2The distance of the B bus can be up to 40 m, and the longest distance between individual nodes can be up to 15 m. Using serial topology instead of ring topology is A2An important element of B technology is vital to the integrity and stability of the overall system. If A2One node of the B daisy chain is affected, and the entire network will not collapse. Only the nodes downstream of the failed node will be affected. And A2The unique built-in diagnostic function of B technology can determine the source and cause of the fault, send out an interrupt signal, and initiate protective measures.

Innovative digital bus architecture reduces audio system costs

Figure 1.A2B functional block diagram of car audio bus.

Compared with the existing digital bus architecture, A2The B master-slave topology itself is more efficient. After starting a simple bus initialization process, the bus can operate normally without more processor intervention. A2An additional advantage brought by B’s unique architecture is that the system delay is deterministic (a delay of 2 clock cycles), and the delay is the same as that of the audio node in A2The position on the B bus is irrelevant. This feature is extremely important for voice and audio applications such as ANC/RNC and ICC, where audio samples from multiple remote sensors must be processed in a consistent manner.

AD2428W, AD2427W and AD2426W A2The B transceiver can transmit audio, control, clock and power signals on an unshielded twisted pair cable. This can reduce the total cost of the system for the following reasons.

u Compared with the traditional implementation, the number of physical cables is reduced.

u The actual cable used can be an unshielded twisted pair with lower cost and lighter weight, rather than a more expensive shielded cable.

u Most importantly, for specific application scenarios, A2B technology can provide low-power power supply and transmit current not more than 300 mA to A2B Audio node on the daisy chain. With this low-power power transmission, there is no need to use local power on the audio ECU, thereby further reducing system costs.

A2The 50 Mbps bus bandwidth provided by B technology can support up to 32 upstream and downstream audio channels using standard audio sampling rates (44.1 kHz, 48 kHZ) and bit widths (12-bit, 16-bit, and 24-bit). This provides considerable flexibility and connectivity for a variety of audio I/O devices. Maintaining an all-digital audio signal chain between audio ECUs can guarantee the highest quality audio quality without any degradation in audio performance due to ADC/DAC conversion.

As mentioned earlier, the system-level diagnostic function is A2An important element of B technology. In all A2On node B, various fault conditions can be judged, including open circuit, wire short circuit, wire reverse connection, wire short circuit to power or ground. From the perspective of system integrity, this function is very important, because in the event of a fault such as an open circuit, a short circuit of a wire, or a reverse connection of the wire, the A at the upstream of the fault point2Node B can still work normally. The diagnostic function also provides the ability to efficiently isolate system-level faults, which is critical from the perspective of the car dealer/installer.

Using the SigmaStudio™ graphical development environment (the same development tools that support ADI’s SigmaDSP® and SHARC® processor series) can greatly simplify the adoption of A2B’s system design process. SigmaStudio initializes A through the industry-leading tool chain2B network, and configure all registers. The SigmaStudio environment also contains A2B bus bandwidth calculator and bit error rate tester (BERT). ADI also provides a large number of full-featured evaluation kits, which can quickly complete the actual A2Prototype design of B network, thus speeding up the early verification and testing, verification and debugging process of the system scheme.

Target market and application

Many mature and emerging market applications will be affected by A2B technology and benefit. Target applications include:

u Audio ECU (car audio host, advanced audio power amplifier) ​​connection

u Microphone array for hands-free calling/voice recognition/in-car communication

u Active noise reduction, road noise active noise reduction

u Personal sound area partition/active speaker

u eCall and telematics system, automatic driving system, automatic parking system

u Vital signs monitoring

u Smart radio connection

Audio ECU connection is a mature and attractive application area. A has been deployed in many mass-produced cars2B. In the simple example where the head unit is connected to an advanced audio amplifier (see Figure 2), A2B There is no need to use multiple cables to connect multi-channel audio, navigation, mobile phones and prompt sounds. A2B can replace all related cables with low-cost unshielded twisted pairs, which pass A2The connection method carried out by B has been tested and verified and meets the most stringent automotive EMC and EMI compatibility requirements.

Innovative digital bus architecture reduces audio system costs

Figure 2. A in the car2B car audio bus example.

Efficient and economical microphone connection is a design priority, leading to a variety of use cases and applications. Bluetooth® connectivity and hands-free/voice recognition systems have become standard features, and emergency call eCall systems have become mandatory requirements in some areas. From the perspective of car manufacturers, the trend is towards the development of multi-microphone (2 to 4) systems that are assembled individually or in units of modules. In any case, use A2The total system cost of B technology is much lower than the cost of analog connections, especially in multi-microphone arrays. All A2B transceivers support up to four PDM microphones to access, so that in the four microphone arrays, three microphone lines in the traditional connection method are saved.

Active noise reduction of road noise is a derivative product of a wider range of ANC applications, and many automakers are evaluating this application. In wideband ANC, it can cancel the sound related to the reference input harmonics, as well as some non-harmonic related or random sounds. These reference inputs are generally provided by acceleration sensors physically distributed around the car body, most commonly in the four suspensions. The other input of the broadband ANC system can come from the error microphone-also distributed inside the car, such as placing one at each passenger location that needs to create a quiet zone. From the connection of each accelerometer/microphone to the broadband ANC processing unit, the traditional implementation uses an analog connection. Obviously, the wiring cost and complexity are too high, and the connector area on the processing unit also needs to be large. And these questions can pass A2Solution B is solved.

For emerging applications that require cost-effective sensor connections, A2B can also be regarded as a technology with a driving effect. Applications such as autonomous driving, vital signs monitoring, and automatic parking systems are expected to begin mass production in 2020, all from A2Benefit from the features, functions, convenience, and fast time to market provided by the B technology.

Summarize

A2B is a digital bus architecture that can provide a series of optimizations for centralized audio and control applications, as well as improve system performance and reduce system costs.

u A2B provides much higher audio quality than analog connections, while also providing a low-cost, scalable digital bus architecture.

u A2B can provide low-risk solutions in various automotive applications.

u Since 2016, based on A2B’s system has entered the deployment stage, and the number of systems currently delivered has exceeded 2 million sets.

u AD2428W and the functionally streamlined and low-cost derivative products AD2427W and AD2426W represent the enhanced function A2The latest development of the B transceiver is dedicated to achieving higher integration and performance in accordance with the established development plan.

The Links:   AA084SB01-T2 FLC48SXC8V-12F

Related Posts

Leave a Reply

Your email address will not be published. Required fields are marked *