📝Article Author: Product Engineer Wen Wenqing from Shenzhen Meige Xin Measurement and Control Technology Co., Ltd.
Currently, many cars are equipped with the A2B bus, mainly benefiting from its simple system configuration, low cost, excellent audio quality, and deterministic low latency. The A2B bus connects audio devices in the vehicle, such as microphones (MIC), amplifiers (AMP), multimedia head units, and T-BOX. It transmits audio data (I2S/TDM), control signals (I2C), clock, and power over a low-cost unshielded twisted pair (UTP) cable. The digital interface eliminates the need for external DAC/ADC conversion, providing a simpler and more convenient solution for audio design while reducing power consumption.
Taking the A2B amplifier audio testing process as an example:
1. The host computer software controls the U 923 and the amplifier for A2B communication, sending multiple test signals to the amplifier;
2. The amplifier outputs an analog signal, and the host computer software collects multiple analog signals through the NI DSA module;
3. The host computer analyzes the signals to complete the testing.
Figure 1. In-vehicle multimedia amplifier audio testing link diagram
Compared to competing solutions in the market, the software AudioExpert is developed based on the NI LabVIEW platform, seamlessly compatible with various NI I/O cards, providing comprehensive multi-channel audio performance analysis. Customers can achieve multi-channel closed-loop testing of A2B power amplifiers/A2B MIC modules using the MegaSig U 923 + NI PCIe platform + S series card solution.
The NI Sound and Vibration module is a dynamic signal acquisition (DSA) device that can accurately measure the frequency components of signals with a very high dynamic range. These modules provide software-configurable AC/DC coupling, anti-aliasing filtering, and IEPE conditioning functions to ensure accurate measurements using microphones, accelerometers, and other transducers with high dynamic ranges.
The PXI sound and vibration modules are designed for applications such as audio testing and measurement, noise and vibration diagnostics, machine condition monitoring, automotive testing, noise, vibration, and harshness (NVH) analysis, and laboratory research.
Figure 2. NI PXI dynamic signal acquisition device
MegaSig U 923 is an analytical solution based on the emerging A2B audio bus testing. The determinism of A2B technology makes it suitable for use in long-distance audio scenarios, and combined with software tools, it can efficiently test various A2B components, such as speakers, audio amplifiers, microphone arrays, sensors, and drivers.
Figure 3. U 923 A2B bus analyzer
U 923 product features:
1. Compatible with AD240x, AD241x, and AD242x, 243x series transceivers;
2. Supports adjustable internal TDM interface, strong compatibility, can generate various types of test signals, supports WAV, etc.;
3. Can simulate as a master node or a slave node;
4. Can read the working current of the slave node;
5. Supports 3.5mm analog input/output interface;
6. Supports S/PDIF input/output interface;
7. Outputs adjustable voltage of 5V-8V to the slave node;
8. Quick configuration of the A2B network via AD Sigma Studio;
9. Has upper-level acoustic analysis software, seamlessly supports AudioExpert and SIO lab, allowing for quick analysis of node signals, such as frequency response, amplitude, THD+N, etc.
Figure 4. MegaSig A2B transceiver testing flow chart
In the future, Shenzhen Meige Xin Measurement and Control Technology Co., Ltd. will actively and continuously explore and expand testing application scenarios in the automotive electronics industry together with the NI China Innovation Development Center, helping engineers create better products and providing high-quality localized services for smart automotive companies and research institutions.
If you are interested in the innovative project “A2B Testing for Automotive Audio Bus,” please scan the QR code below to contact the NI China Innovation Development Center.
