STM CircleOS forum / Possible crazy project (bit-banging a proprietary RJ45 based bus)

Kybertech · 2010-10-03 23:52:22

Its about the so called A-Net, Audio over Ethernet bus. These devices are used in big studios and they are dirt cheap on ebay. (In comparison to a consumer level Firewire or USB multichannel interface)
The physical Layer is identical with Ethernet, so the possible best way to do this is a high end FPGA prototyping board. But I don't have an extra 2k bucks to spare and if I did I would just buy a decent recording interface.

So I thought there might be another way:
Obviously the STM32 wouldn't be able to keep up but (and here comes the big if)
It might be possible to use a CPLD in-between the extension port and the RJ45 bus. If the protocol would be based on a 100mbit Ethernet variant the CPLD should be fast enough to stuff the extension port using whatever widest bus which could be implemented.

In theory possible but there are problems:
⚫ The protocol uses a 24bit sample-rate and full duplex mode.
⚫ The STM32 wouldn't be able to keep up with the full clock speed (obviously).
⚫ Because of the above some asynchronous bus would have to be implemented.
⚫ There might be no way to reverse engineer the protocol without a high-speed data-logger on the pc and forensic software. (But I might be able to get access to a lab, but fuck that's a bad one )

The rest should be challenging but certainty possible:
⚫ Depending on the Protocol I would need a low latency code to assemble the samples.
⚫ Writing a USB audio driver has not been done here. or has it?

I would appreciate any insights on anything. Thank you.

wincent · 2010-10-05 19:13:13

Hello,

if I am not mistaken, STM did an example implementation of an USB Audio device in it's STM32 USB library.

Sincerely yours,

wincent

Kybertech · 2010-10-06 04:58:18

Thanks,

I didn't know that, however I decided against buying such a device, I've seen some complaint about the usb bandwidth practically available on the primer2, the input channels alone would have 18mbit.

Instead I will try my luck with my minidisc 4track, I don't know yet where exactly to intercept the data but there are more possibilities to play with and I won't need a CPLD
The most interesting thing might be a point between the md-data drive and the AD/DA heh

# 1 2010-10-03 23:52:22 Possible crazy project (bit-banging a proprietary RJ45 based bus)

Possible crazy project (bit-banging a proprietary RJ45 based bus)

# 2 2010-10-05 19:13:13 Possible crazy project (bit-banging a proprietary RJ45 based bus)

Re: Possible crazy project (bit-banging a proprietary RJ45 based bus)

# 3 2010-10-06 04:58:18 Possible crazy project (bit-banging a proprietary RJ45 based bus)

Re: Possible crazy project (bit-banging a proprietary RJ45 based bus)

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