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Old 19th October 2012, 11:58 PM   #11
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24-bit audio PIC32-based developments boards

Could be useful for a low cost two way dsp active crossover


Part Number: DM320014

The PIC32 USB Digital Audio Accessory Board showcases a 16/24-bit quality digital stereo audio development platform using the PIC32 microcontroller (MCU). It can be used for 16/24-bit stereo audio playback and recording with a sample rate of up to 48 kHz. This accessory board is powered by the USB Host and can be used with any personal computer (PC), tablet, gaming station, or mobile device that supports the USB Audio Device Class. The digital audio stream is transferred over USB isochronous transfers. The PIC32 USB Digital Audio Accessory Board features the PIC32 MCU, which has a USB module with Host and Device capability, SPI module with Audio Mode that supports I2S, LJ, RJ, DSP/PCM modes, and a flexible audio reference clock output generation module that can be used as time base for the external codec or Digital-to-Analog Converter (DAC).

Key Features:

PIC32MX250F128B MCU: 40 MHz, 128 KB of program memory and 32 KB of RAM
PIC32 I2S support (LJ, RJ, DSP/PCM modes supported) Ė all modes can be 16/24-bit
PIC32 reference clock output for codec master clock
Audio codec (AK4645A) with up to 48 kHz sampling rate and 16/24-bit resolution
Supported codec-based audio processing features:

o 5-band equalizer

o Analog output mixing

o Stereo separation emphasis and wind-noise filtering

o Auto-level control
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Old 11th February 2013, 02:09 PM   #12
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Originally Posted by mixtricks View Post
Is there a way I can calculate coŽfficiŽnts for a LPF @ 500Hz and somehow "merge" them with the coŽfficiŽnts for the HPF at 2K8? Can sets of coŽfficiŽnts be combined somehow?
Hello Igor, "merging" is combining the two filters (500 Hz lowpass and 2K8 lowpass) for feeding one of the two midbass drivers. It should work painless if both lowpass filters are phase-linear and time-aligned.

You'll need to add a global shelving equalizer at the signal input for restoring global amplitude linearity.

However, dealing with a 500 Hz lowpass and a 500 Hz shelving eq with Fs 96 kHz, I'm not sure that 121 taps are sufficient.

Try doing the 500 Hz job in analog using a 1st order passive lowpass, just like Philips DSS930 did.
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Old 11th February 2013, 02:21 PM   #13
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Originally Posted by Trevor White View Post
Microchip DM320014 24-bit audio PIC32MX2-based developments board
At $69.99, this is indeed a nice opportunity. Source code is going to be interesting, especially the USB-audio function (really working like any USB-audio soundcard?) and the I2S codec interfacing. Have you got the opportunity to try it? How many MIPS consumed by the USB-audio process? How many MIPS remaining for audio DSP?
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File Type: jpg Microchip DM320014.jpg (32.7 KB, 163 views)

Last edited by steph_tsf; 11th February 2013 at 02:27 PM.
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Old 13th February 2013, 01:14 AM   #14
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Today I went looking the Microchip DM320014 USB Digital Audio Accessory Board.
I've downloaded and looked the demo sources files available from Microchip website. Audio comes from USB (isochronous), and gets played by the AK4645a audio codec. They call this a "High-Quality Audio Application", however they continuously adjust the master clock sent to the AK4645a codec for software-emulating the fractional divider that's required from the USB clock, for avoiding buffer underrun errors.
I guess most people will get frightened by the complexity of the source code.
Can you believe, seeing this I'm regretting my old DSP56002 EVM coupled to the Domain Technologies debugger running under Windows 3.11. This is more than 15 years ago. The audio codec was a CS4215. Happy memories. A few pictures attached.
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File Type: jpg DSP56K assembly.jpg (165.1 KB, 146 views)
File Type: jpg Medical Office.jpg (86.2 KB, 142 views)
File Type: jpeg DSP56002 EVM.jpeg (73.9 KB, 146 views)
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Old 13th February 2013, 01:00 PM   #15
qusp is offline qusp  Australia
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seems simpler to just use a larger buffer....
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Old 5th November 2013, 10:59 PM   #16
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For the sake of clarity, re-uploading the FIR crossover arrangement that appears to perform best.
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File Type: png 2000 Hz 3rd-order.png (70.6 KB, 107 views)
File Type: png 200 Hz 3rd-order.png (63.3 KB, 35 views)
Attached Files
File Type: zip iDFT XO (218.5 KB, 17 views)
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