Subject: Re: [linux-audio-dev] Echo Darla/Gina/Layla/... on Linux
From: Lamar Owen (lamar.owen_AT_wgcr.org)
Date: Mon Mar 24 2003 - 19:27:23 EET
On Monday 24 March 2003 08:35, David Olofson wrote:
> On Friday 21 March 2003 21.47, Paul Davis wrote:
> > agreed. its a rather tricky design however, because on a lot of
> > hardware, you have to defer most of the driver initialization until
> > the firmware load is complete. the h/w won't even talk to you
> Just to make things more fun, it seems that Echo put some programmable
> logic in the external part of Layla. (Only the DSP is on the PCI
> card.) Problem is that the external box has it's own power supply,
> and a switch on the front panel, and may well be powered off when you
> start up the computer. If that happens, the driver must delay the
> initialization until the external box is powered on.
It's an FPGA, IIRC. All the codecs and such are in the external box, and the
FPGA does all the signal routing and may do some DSP work (for output monitor
matrix and volume). The Layla's output monitoring capabilities are quite
powerful, with any input available for monitoring to any output, with
multiple inputs to multiple outputs allowed. So the FPGA must do some mixing
for all 12 possible outputs, where each output may have anywhere from zero to
eight inputs assigned. Since the S/PDIF I/O is included in the matrix
possibilities (both as an input and an output), but has no level control on
either inputs or outputs, I would hazard a guess that the input and output
level controls are implemented as digitally controlled volume control chips,
and the FPGA probably only does minimal mixing in the S/PDIF domain.
I can open my Layla to make sure; just not today.
The few times I've tried the 'switch the external box off with PC up' routine
have all caused problems at some point.
-- Lamar Owen WGCR Internet Radio 1 Peter 4:11
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