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[FAQ] PurePath Console Motherboard

PurePath Console Motherboard

Wiki entries for PurePath Console Motherboard (aka PPCMB)

http://www.ti.com/tool/purepath-cmbevm

How to configure PPCMB for external audio interfaces

The PurePath Console motherboard can be configured to accept audio from multiple interfaces. This wiki page explains how to change between the default configuration (USB Audio) and external audio (PSIA).

The IO expander included in the controller board is used to select which I2S source is streamed to the daughter board; The control of the expander is done via software. 

Considerations should be taken according to the revision of the PurePath Console motherboard:

  • If PurePath Console motherboard Rev. D. is used, the installation of a 0-ohm resistor at R312 is required to allow control of the audio interface muxes. 
  • There is no HW requirement if using PurePath Console motherboard Rev. F. or later. 

Load the desired script below by using the command-line interface of PurePath Console GUI.


For External (PSIA) Audio Interface

##########################################################
# PSIA as MCLK/I2S source
##########################################################

# Change to GPIO mode
i gpio
# Set bank 0
w 99 04 01
# Clear bits (command 01) with mask 20 - clears P1.5 of Bank 0
w 99 01 20

# Go back to I2C mode
i i2cfast
# Set pins 21-24 as outputs
w 44 0E 0F
# Set pin 23 high (MCLK-MUX = PSIA)
w 44 06 7F


For USB Audio / Optical / Coax Interface

##########################################################
# AIC3262 as MCLK/I2S source
##########################################################

# Change to GPIO mode
i gpio
# Set bank 0
w 99 04 01
# Set bits (command 00) with mask 20 - sets P1.5 of Bank 0
w 99 00 20

# Go back to I2C mode
i i2cfast
# Set pins 21-24 as outputs
w 44 0E 0F
# Set pin 23 low (MCLK-MUX = AIC3262)
w 44 06 3F

PPCMB Analog input setting for PurePath Console 1 and 2

    When using the analog input of the PurePath Console motherboard, a roll-off phenomenon will appear when usign PurePath Console software (PPC1 and PPC2). This issue is related to the configuration of the ADC that converts the analog input to the digital data that is sent to the device under test.

To fix this, a single line command should be written via Direct I²C tab in PPC1 and PPC2:

PurePath Console 1:

    • On Direct I²C Access tab, set Device I²C address to 0x88
    • On Command Buffer Interface, write the following code, then, click on Execute.  

X53 3F

    •  Set the Device I²C address as default. 

 PurePath Console 2:

    • On Direct I²C Read/Write tab,  write the following code, then, click on Execute.  

 W 88 53 3F

 

PPCMB RevD analog inputs are distorted

Applies to:

PurePath Console Motherboard Rev A to Rev D


These PPCMB revisions exhibit an issue when using analog inputs AIN1 and AIN2. There are two causes for this distortion: instability of the OA1-OA2 amplifiers and clipping.

The instability issue can be easily fixed by removing C206 and C213 as shown below.

The clipping issue is caused by the MUX2 analog switch. The input op-amps bias the signal to 2.5V, but the analog switch operates at 3.3V. This means that only ~0.8Vp signal swing is available. For RevD, the workaround is to keep the AIN1 and AIN2 input signal at or below 500 mVrms.

These and other issues will be fixed for the Rev E version of the board.

Purepath Studio FAQ

 

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