Project:Digital Audio

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Digital Audio Stereo
NexusQ hooked to custom speaker
NexusQ hooked to custom speaker
Started
Date 1/14/2014
signature

The NexusQ is an abandoned media streaming device by Google. The device is unique that it includes a "stereo-grade" amplifier for outputting audio directly to analog speakers. The device uses a TAS5713 25 watt class-D amplifier and an integrated 35W switching power supply. This project is to rescue the amp by hooking it to a small computer (targeting the BBB).

The current phase is discovering the pin-outs and learning how to "activate" the 35W switching power supply.

Goals/Problems

Control the amp from a computer and then incorporate into a nice active stereo system.

Materials

  • NexusQ parts
  • Single board computer, beagle bone black
  • Full range speakers

Nexus Q TAS5713 Pin-out

Nexus Q Amp Bus.png Nexus Q tas5713 bus data pins.png

Here is what we know (thanks to someone special).

  1. GND (correct)
  2.  ??? (should be CHASSIS_GND)
  3. GND (correct)
  4. N/C (correct, there is no pin or pad here)
  5. 3.3V (should be 3.8V)
  6. 3.3V (should be 3.8V)
  7. 3.3V (should be 3.8V)
  8. 3.3V (should be 3.8V)
  9. AVDD (should be DVDD and 3.3v, but bridged to AVDD via R6 on the audio board)
  10.  ??? (should be N/C. This pin was used for a circuit which is no longer present on the production boards)
  11. GND
  12. GND
  13. SCL
  14. SDA
  15. GND
  16. GND
  17. DVSSO (should be SCLK)
  18. LRCLK
  19. SDIN
  20. MCLK
  21.  ??? (should be RST_N)
  22. PD_N
  23. GND
  24. GND

Some clarifications.

  • CHASSIS_GND is just what it sounds like. It is separated from the main GND with an RC circuit on the audio board and should remain that way.
  • The main 3.8V power signal comes from the power supply board, through the audio board and goes to the digital main board. The various regulators for the main board produce the 3.3V which is sent back to the audio board and supply (non-amplifier) power to the TAS5713. If you are removing the digitial main, but using the Q's power supply, you will need to provide 3.3v somehow. If you have no plans to use the Q power supply, you should be able to provided 3.3v to the 3.8v rail and just tie pin 9 to pins 5-8.
  • The digital interface to the amplifier is 3.3v. If you are using a uC running with 1.8v digital pins, you will need a set of level converters. Level converters (particularly the bi-directional LCs needed for I2C) can be tricky. Use caution in your design.
  • The power stage of the amplifier itself needs a solid 24v rail.
  • The 24v section of the Q's PS interfaces to the audio board via a 5 pin header. 2 GND signals, 1 digital IO power rail (should be 3.8v, although older schematics had it marked as 5v), 1 24V amp rail and a shutdown signal for the 24v rail. The shutdown signal is produced on the audio board as a combination of the RESET and POWERDOWN signal from the digital main and will shut down the 24v section of the power supply to save power when the amplifier is idle.

BBB Pin-out for I2S

  • bit clock on 31, L/R on 29, data on 28
  • P9_25 SCK or master clock

Links

TAS5713 Driver

Participants

JarrettV (talk) 13:58, 15 January 2014 (CST)Jarrett Vance

Progress/Updates/Workshops

1/14/2014

We identified 4 out of 5 pins on the power supply. We identified the ground and power pins on the amplifier.

Pictures

NexusQ Opened.jpg
NexusQ TAS5713.jpg