Re: USB host chips
From: Ulf Samuelsson (ulf_at_atmel.nospam.com)
Date: 11/11/04
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Date: Thu, 11 Nov 2004 20:44:20 +0100
> > I'm currently looking at USB host chips from Atmel and Cypress. Has
> > anyone had experience writing host side software using chips from
> > either of these companies, and what were your experiences? Thanks.
>
> I was involved in a project to access mass-storage devices (only) from a
> legacy embedded system. Quite nightmarish. I'd say that the software
> effort involved is going to be roughly the same for any of these
> devices; i.e. very large, and you'd be happier using an OS that already
> has driver support for the chip in question (Linux for instance has
> support for the Cypress low-end part).
>
> The bigger problem is that USB devices are frequently - I might say,
> USUALLY - not fully standards-compliant. So, your device won't be
> "universal" unless you become aware of and implement workarounds for a
> bunch of undocumented incompatibilities, and this process is ongoing for
> as long as you intend to support the appliance :(
>
> Atmel does have a chip that does everything for you in on-chip firmware,
> but it's expensive and (more important for my application), could not be
> accessed over an 8-bit bus.
Hi Lewin, this was the AT43USB370.
There is a new chip now, the AT43USB380 which allows
8, 16 and 32 bit interface and also has OTG functionality.
(You need an extra small chip if OTG is required, and this is not available
yet)
Have now plenty of people working on the ATmega128 and the AT43USB380.
For Mass Storage you need about 63 kB of code, so the m128 will
allow some applications to be added as well.
You may need some external SRAM as well, so some people plan to use the
ATmega2561 which has 8 kB of SRAM and is pin compatible.
If you just need a device which allow you to connect to the USB standard
mass storage adapter,
then the driver is about 20 kB less, but then it is, as you indicate, pretty
useless.
-- Best Regards, Ulf Samuelsson ulf@a-t-m-e-l.com This is a personal view which may or may not be share by my Employer Atmel Nordic AB
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