Friday, August 10, 2012

Audio Features

Think I've located some products to start planing the audio section around. I've added an advanced audio settings page based on the features available on the TDA7718N. Basically this is a nice little DSP chip that has an IC2 interface that I'll be able to use the PicMicro to program the settings of.

Tentative Parts List

TDA7718N  (DSP Chip for sound/volume control)

Si4735 FM/AM Radio Receiver Breakout (am/fm tuner board with RDS support and IC2 interface)

Redpark TTL cable for iOS (cable and development SDK to get the iPad and PicMicro connected)

Sample Video of added audio settings

Its a bit difficult to make out what things are present on the advanced page but they are as follows:

Treble with -15dB to + 15dB range
Center Freq. selection of 10kHz, 12.5kHz, 15kHz, 17.5kHz

Mid with -15dB to + 15dB range
Center Freq. selection of 500Hz, 1kHz, 1.5kHz, 2.5kHz
Q setting of .75, 1.0, 1.25

Bass with -15dB to + 15dB range
Center Freq. selection of 60Hz, 80Hz, 100Hz, 200Hz
Q setting of 1, 1.25, 1.5, 2

Subwoofer cut off frequency 55Hz, 85Hz, 120Hz, 160Hz

Main audio settings page will retain balance, fade, subwoofer level and turning internal amps on/off

Looks like I will be able to get most of the audio features found on your typical headunit including controls for a subwoofer output! For this project I plan to use some of my old audio stuff! 

Items to still workout
  • To go only with pre-outs to run to external amps or build/buy Chip amp solution to retain use of factory audio system. (or possibly both)
  • To Sirius/XM or not... looking like it would require buying an add-on tuner for an aftermarket headunit and hacking it up to talk to the PicMicro to be controlled via the iPad interface...
  • Pre-amp to boost up the audio signal from the TDA DSP chip to something around the 4 volt mark... would like to use some Burr Brown chips I have laying around from a past project... they seem to work nice!
  • To get an apple iOS developer account or not... would like to do this without but the more I read the more imposible apple has made it to program in xCode and get it on an iDevice without... 

If anyone has suggestions for DSP chips well suited for car audio or some decent pre-fab preamp circuits to cut down on development time I'd love to know about them! This project scope is expanding rapidly and I'd like to be able to finish before its time to buy a newer car... lol

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