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How Can I Best Monitor Data and Phantom Power on the A2B Bus?
Rena Ayeras

Question from the Customer:

I’m looking at the A2B Bus Monitor - Level 1 Application for an audio system.  I have some questions:

  • How many total channels are available? Our system has multiple channels per board.
  • How is the SigmaStudio® software used within the system?
  • Can we capture data in formats other than .WAV file?
  • Could I monitor the phantom-power values?
Response from Technical Support:

Thanks for your questions!  The A2B Bus Monitor - Level 1 Application is designed for bench top prototyping and in-vehicle field testing. It is a passive monitor that non-intrusively sniffs A2B data, providing real-time access to the data traffic. This access to data supports analysis, troubleshooting, and validation. For more information, please refer to this datasheet.  Please note the A2B Bus Monitor Application runs on the Promira Serial Platform.

A2B is a proprietary protocol developed by Analog Devices.

What the A2B Bus Monitor Supports

The following sections describe what the A2B Bus Monitor provides for your setup.

Number of Channels

The A2B Bus Monitor supports 16 channels upstream and 16 channels downstream concurrently. Here is how the channels are used:

  • The ADI sniffer chip (which is on the A2B adapter board), will use the first two channels (numbers 0 and 1), both upstream and downstream for the Synchronization Control Frames (SCF) and Synchronization Response Frames (SRF).
  • The .wav file will have 14 channels of upstream and 14 channels of downstream audio.
Note: You can export less than the maximum number of channels, but that would not affect the maximum length of the .wav file.

Using SigmaStudio

SigmaStudio is a graphical development tool that is provided by Analog Devices. One of our KB articles, Using Total Phase I2C Tools with the A2B Bus Monitor for Full System Emulation, provides guidelines about using SigmaStudio with Total Phase tools.

For detailed information about using SigmaStudio, please refer to SigmaStudio and SigmaDSP Documentation.


Data Capture Formats

  • Up to 15 seconds of audio data can be exported as a multi-channel WAV file.
  • When using the Data Center Software, captured bus data can be exported as a CSV file.

Monitoring Phantom Power

The A2B Bus Monitor can monitor a phantom powered slave; however, the A2B Bus Monitor cannot trace the specific power values.

About Phantom Power

In automotive technology, phantom power is used to deliver power to remote nodes. The power source is effectively “invisible”; a distinct power supply is not connected to any of the nodes. Instead, power is delivered from the power source up the same wires that are used for delivering audio signals. This saves the cost, labor, and design of adding more wires to the automotive head unit. Because the power is DC (direct current), the signals delivered on the A2B bus are not distorted.

We hope this answers your questions. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.

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