From: john cooper <john.cooper_at_third-harmonic.com>
Date: Fri, 10 Apr 2009 10:11:47 -0400

Jorge Pinto aka Casainho wrote:
> Hello :-)
>
> As I said before, we are working on Lyre project, a Free/Open hardware
> audio player
> (DAP) and recorder, for use with RockBox firmware.
>
> We will probably use an SD Card for hold the audio files and for easy
> the life of users for sharing music (I mean music with Creative Commons
> license and the recorded by users).
>
> My question is: is the USB really need if we have an SD Card? would
> users still miss the USB?

Ok, here is where the issue of 1-bit SPI mode vs. 4-bit SD
mode may become an issue. SPI is fine for pulling data from
the card at compressed audio stream rates. But if you are
using it to transfer bulk data as in the case of
down/uploading from a host PC, it could be unacceptably slow.

And unless you have an SPI controller shuffling data to/from
the card at 25Mb/s is going to be a challenge.

> 2nd question: if we need to use USB, does we need to pay royalties for
> use it?

Again IANAL but have a look here:

     http://www.usb.org/developers/logo_license

The issues are whether you want to use the USB logos
and more importantly getting a VID. I have no idea
what degrees of maneuvering freedom exist around not
paying for a unique VID.

-john

-- 
john.cooper_at_third-harmonic.com

Received on 2009-04-10