RE: AT91 ADC support

["Christophe Coutand" <ccoutand@stmi.com>]

Hi John,

It's pretty easy to add the required definition for the AT91M55800A
targets. The only thing I see now is that this device contains 2 ADCs
which I have not considered before. I guess there are several ways out
of this:

1- Update the actual AT91 ADC driver to make full use of the AT91M55800A
targets. I guess should be done by loading a second ADC instance (one
for each ADC. I have not been through all the thinking here...).

2- or limit the AT91 driver to use only ADC0 of the AT91M55800A target
for the time being.

3- or exclude AT91M55800A targets for the time being.

IMO #1 is best but I cannot give any time frame for completing it.

One additional weakness of the driver is that it is made for up to 8
channels. It is defined nowhere what the targeted CPU can actually
handle, this is left to the user when configuring eCos. I believe this
is pretty fine since the user must anyway know which signal he wants to
sample but you might disagree on that one.

Regards,
Christophe


-----Original Message-----
From: John Dallaway [mailto:john@dallaway.org.uk] 
Sent: 27. mai 2010 16:48
To: Christophe Coutand
Cc: Sergei Gavrikov; ecos-patches@ecos.sourceware.org
Subject: Re: AT91 ADC support

Hi Christophe

Christophe Coutand wrote:

> I originally made it for AT91SAM7S and AT91SAM7X but at the last
minute
> I saw that Atmel was using the same ADC for AT91M55800A, AT91SAM9X
etc..
> so I renamed it to AT91. I thought this would be more future proof.

It's definitely a good idea to keep the package name more generic.

> It remains true that I have not compiled / tested it for anything else
> than AT91SAM7S / AT91SAM7X.
> 
> I can specify which AT91 supports it and update the var_io.h when
> definition are missing.

If it's easy to get the package building for the AT91M55800A targets
(eb55, phycore) then that would be preferable. If not, we can add the
package to the AT91SAM7 targets only (at91sam7sek, at91sam7xek,
sam7ex256) for now.

John Dallaway
eCos maintainer