Low delay 50mbps communication! Analog Devices' new serial bus A2B

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Macnica Engineer

Low delay 50mbps communication! Analog Devices' new serial bus A2B

 "A2B" simplifies communication and lowers costs

This article introduces Analog Devices' new "A2B" transceivers.

A2B is an abbreviation for "Automotive Audio Bus." As the name suggests, it is a new technology developed with the aim of reducing the weight (fuel efficiency) and cost of audio harnesses used in in - vehicle infotainment systems, which are becoming increasingly popular. In addition to Ford Motor Co. of the United States, several other manufacturers in Japan, the United States, and Europe are planning to this bus in mass - produced vehicles, and it is expected to become a standard communication bus for the car audio industry in the near future.

This time, we will introduce the three major features of "A2B" and the expected benefits in electronic and industrial equipment.

1. 50 Mbps communication, I2C/I2S signal is transmitted with low delay of 50 μ sec.
2. Up to 40 UTP for up to 40m data
3. Simple design system.

50Mbps communication, I2C/I2S signal is transmitted with low delay of 50μ sec

A2B is possible to communicate at a data rate of 50Mbps using a simple cable, and since it does not require the intervention of the software stack on the slave side, there is only a 50μ sec delay between nodes even connected in a daisy chain.

Among the various existing communication standards, I2C is in the position shown below, but the use of A2B extends the usability of I2C and plays a complementary role to Ethernet.

Comparison of communication speed / distance and A2B for each communication standard

Up to 40 UTP for up to 40 meters of data

A2B functional block diagram

Only a pair of unshielded twisted pair (UTP) cables are required for communication. Since no special cables are required, wiring between boards can be reduced, and system simplification and cost reduction can be expected.
                                                 
Communication distance is up to 15m between nodes, and by connecting nodes, communication of up to 40m in the system is possible. The devices are separated by master / slave and have a maximum of 10 channels.

Function Comparison Table by A2B Type
A2B Part No.
 		 Master
AD2428		 Slave
AD2427		 End dedicated slave
AD2426		 Low cost master
AD2429    		 End dedicated low cost slave
AD2420
TRX functional block A + B  A + B A B A
I2S/TDM support Yes No Yes Yes No
PDM Microphone Input Count 4 4 4 4 2
Maximum number of slave connections 10 - - 2 -

Maximum cable length between nodes

 15m 15m 15m 5m 5m

Simple design system

A2B does not require a software stack or storage memory on each node and does not impose any processing load on the connected processors, enabling I2C and I2S communication to scale with maximum design simplicity.

The physical layer is a low - amplitude differential signal (LVDS) that is resistant to noise. In addition to the signal, it can supply a clock and a DC voltage of + 5V/300mA, so that it can supply bus power for sensors and microphones.

You can also configure devices visually using the SigmaStudio® Graphical Software Tool.

Simplify systems with A2B
Simple expansion of I2C and I2S

 

Performance and EMC evaluation boards available

Analog Devices has multiple evaluation boards to help speed up performance evaluation. There are four basic types of A2B evaluation boards:

Order Number EVAL-AD2428WD1BZ EVAL-AD2428WB1BZ EVAL-AD2428WC1BZ EVAL-AD2428WG1BZ
Master/Slave Master Slave only Slave only Slave only
Power supply Local powered PPS: Phantom Powered Slave PPS: Phantom Powered Slave LPS: Phantom Powered Slave
Audio in/out 3.5mm mini jack and Optical-SPDIF 3.5mm mini jack None 3.5mm mini jack
PDM mic 2-ch 2-ch 4-ch None
Board image

Main Functions of A2B Master Device "AD2428"

A2B bus function

  • Line topology
    • single master, multiple slaves
    • Up to 15 nodes, 40m maximum cable length
  • Telecommunications
    • Synchronous data
    • Multichannel I2S/TDM - I2S/TDM
      • Clock synchronization, phase alignment on all nodes
      • Communication between low delay slaves
    • Control and status information I2C - I2C
    • Far GPIO
  • Bus power or local power slave node
  • Configurable using SigmaStudio ® graphical software tools

A2B Transceiver Function

  • Can be set as A2B bus master (supports up to 10 slaves) or slave
  • I2C interface
  • 8 - bit to 32 - bit multi - channel I2S/TDM interface
    • programmable I2S/TDM data rate
    • Up to 32 Upstream and 32 Downstream Channels
  • PDM interface
    • Four high dynamic range microphone inputs
    • programmable sampling rate
    • Performs 24 - bit PCM demodulation
  • Supports receiving I2S data on nodes using up to four PDM microphones
  • Unique ID register for each transceiver
  • Crossover or straight - line cable support
  • Programmable settings that optimize EMC performance

Application Example

  • Conference system
  • Call center
  • Large equipment

 

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