Hi all
So i'm trying to extract some digital audio from a particular car stereo. It's a Sony MEX-BT4100U (current 2013 model). It has input sources: AM/FM tuner, CD transport, USB media, Analogue AUX in and Bluetooth audio.
I've been picking through the service manual (https://docs.sony.com/release/MDSM/989355102_sm.pdf) and it appears that, typically, it's one big analogue switcher with modern digital bits bolted on.
Here's my interpretation of the block architecture for signal path:
So my best hopes for anything pure digital from this unit are USB and/or CD audio. From what I can gather, the CD transport (DAX-25A), outputs a raw signal which the Sony ASE chip handles (it's described as a Head Amp).
It appears they have implemented a 32-bit ARM micro (!) mainly to handle USB comms/filesystem stuff. This seems to send audio digitally to the ASE/DSP chip using the 'BSIF' protocol. I was hoping for I2S but the datasheet for the MCU specifies multi-purpose ports, supporting I2S, SSP (SPI/Microwire) and BSIF.
Unfortunately I know nothing about BSIF and can hardly find anything about it on-line.
My goal is to get a clean digital output from either the CD transport or USB media source. I have a feeling the CD one would be very difficult. The USB option isn't looking particularly wonderful either. My logic analyser supports protocol definition for I2S but not BSIF.
Any thoughts on this folks? 🙂
So i'm trying to extract some digital audio from a particular car stereo. It's a Sony MEX-BT4100U (current 2013 model). It has input sources: AM/FM tuner, CD transport, USB media, Analogue AUX in and Bluetooth audio.
I've been picking through the service manual (https://docs.sony.com/release/MDSM/989355102_sm.pdf) and it appears that, typically, it's one big analogue switcher with modern digital bits bolted on.
Here's my interpretation of the block architecture for signal path:
So my best hopes for anything pure digital from this unit are USB and/or CD audio. From what I can gather, the CD transport (DAX-25A), outputs a raw signal which the Sony ASE chip handles (it's described as a Head Amp).
It appears they have implemented a 32-bit ARM micro (!) mainly to handle USB comms/filesystem stuff. This seems to send audio digitally to the ASE/DSP chip using the 'BSIF' protocol. I was hoping for I2S but the datasheet for the MCU specifies multi-purpose ports, supporting I2S, SSP (SPI/Microwire) and BSIF.
Unfortunately I know nothing about BSIF and can hardly find anything about it on-line.
My goal is to get a clean digital output from either the CD transport or USB media source. I have a feeling the CD one would be very difficult. The USB option isn't looking particularly wonderful either. My logic analyser supports protocol definition for I2S but not BSIF.
Any thoughts on this folks? 🙂
It's difficult to see what would be hackable, but in any digital audio system, you can always pick off the I2S data and clocks and plop that onto your physical DAC & analog stage.
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