AVR-Chat

Hi all,

 I've been a little out of touch with AVR's of late, and was surprised to
see the XMEGA part on the web site. Looks like a very capable little chip -
lots of goodies built in that could be very useful. When did it come out?
The datasheet revisions date back to 2008 - I must have been living under a
rock.

The project is a datalogger for automotive use, and the XMEGA part looks
quite attractive, but I'm still undecided on the storage side.

I understand that dataflash is fast, but realistically what sort of speeds
could I expect if I used an SD card for data? SD would offer a much larger
capacity than dataflash, and low cost too, but how well do they go?

Anyone here with experience with both? I have quite a number of 64Mbit
dataflash chips on hand so it would make sense to use them, but I dont want
to compromise the design just because the parts are on the shelf.

Thanks
Dean


[Non-text portions of this message have been removed]

--- In AVR-Chat@yahoogroups.com, Dean Claxton <deanclaxton@...> wrote:
>
> Hi all,
> 
>  I've been a little out of touch with AVR's of late, and was surprised to
> see the XMEGA part on the web site. Looks like a very capable little chip -
> lots of goodies built in that could be very useful. When did it come out?
> The datasheet revisions date back to 2008 - I must have been living under a
> rock.
> 
> The project is a datalogger for automotive use, and the XMEGA part looks
> quite attractive, but I'm still undecided on the storage side.
> 
> I understand that dataflash is fast, but realistically what sort of speeds
> could I expect if I used an SD card for data? SD would offer a much larger
> capacity than dataflash, and low cost too, but how well do they go?
> 
> Anyone here with experience with both? I have quite a number of 64Mbit
> dataflash chips on hand so it would make sense to use them, but I dont want
> to compromise the design just because the parts are on the shelf.
> 
> Thanks
> Dean
> 
> 
> [Non-text portions of this message have been removed]
>


The speed has two timing requirements.

1) actual speed of the part to transfer to its internal buffer
2) write speed.

Dataflash and SD cards are basically the same speed, limited by the SPI port clock.

The biggest problem with SD cards is the assumptions about FAT16/FAT32.

In the Dataflash you can write in a serial fashion with data flowing to the next block.

With FAT files you need to know where to put the next block and to do that you need to read the directory and FAT table.

After each block write it would be best if you re-wrote the FAT table so in case of a power failure, you would know where you left off.

There has been discussion about "pre-formatting" the FAT table and directory so that your code can just use the "next block".

But if someone sticks in a SD card with other data on it, it may be over written by you code.

Google has some interesting test results for SD cards in cameras and SPI testing.

good luck, let us know how you get along.

don

If you're making a product for sale, be sure to read the license terms of
each technology before deploying. It's possible that you may decide that one
tech is better than the other for non-technical reasons. I'm not familiar
with Dataflash, but I can tell you that in order to include a SD card slot
in your product you are required to join the Secure Digital Association,
which costs a couple thousand dollars, and to pay annual license fees per
product, which are thousands more. It's been a while since I looked, but I
believe it was around $5000 for the first year and $2-3k for all future
years if you sell only one product. The price is regardless of whether you
sell one board or millions.

I suspect that you could make a small hobbyist board without having to worry
about the license fees, but it is something that you should be aware of.

On Mon, Feb 1, 2010 at 3:22 AM, Dean Claxton <deanclaxton@gmail.com> wrote:

> Hi all,
>
>  I've been a little out of touch with AVR's of late, and was surprised to
> see the XMEGA part on the web site. Looks like a very capable little chip -
> lots of goodies built in that could be very useful. When did it come out?
> The datasheet revisions date back to 2008 - I must have been living under a
> rock.
>
> The project is a datalogger for automotive use, and the XMEGA part looks
> quite attractive, but I'm still undecided on the storage side.
>
> I understand that dataflash is fast, but realistically what sort of speeds
> could I expect if I used an SD card for data? SD would offer a much larger
> capacity than dataflash, and low cost too, but how well do they go?
>
> Anyone here with experience with both? I have quite a number of 64Mbit
> dataflash chips on hand so it would make sense to use them, but I dont want
> to compromise the design just because the parts are on the shelf.
>
> Thanks
> Dean
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>


[Non-text portions of this message have been removed]

Ouch - thanks for that Mike - that may well tilt me away from SD. Do all the
other card formats have similar licencing?

Dean

On Tue, Feb 2, 2010 at 4:58 AM, Mike Payson <mike@kludgineering.com> wrote:

> If you're making a product for sale, be sure to read the license terms of
> each technology before deploying. It's possible that you may decide that
> one
> tech is better than the other for non-technical reasons. I'm not familiar
> with Dataflash, but I can tell you that in order to include a SD card slot
> in your product you are required to join the Secure Digital Association,
> which costs a couple thousand dollars, and to pay annual license fees per
> product, which are thousands more. It's been a while since I looked, but I
> believe it was around $5000 for the first year and $2-3k for all future
> years if you sell only one product. The price is regardless of whether you
> sell one board or millions.
>
> I suspect that you could make a small hobbyist board without having to
> worry
> about the license fees, but it is something that you should be aware of.
>
> On Mon, Feb 1, 2010 at 3:22 AM, Dean Claxton <deanclaxton@gmail.com>
> wrote:
>
> > Hi all,
> >
> >  I've been a little out of touch with AVR's of late, and was surprised to
> > see the XMEGA part on the web site. Looks like a very capable little chip
> -
> > lots of goodies built in that could be very useful. When did it come out?
> > The datasheet revisions date back to 2008 - I must have been living under
> a
> > rock.
> >
> > The project is a datalogger for automotive use, and the XMEGA part looks
> > quite attractive, but I'm still undecided on the storage side.
> >
> > I understand that dataflash is fast, but realistically what sort of
> speeds
> > could I expect if I used an SD card for data? SD would offer a much
> larger
> > capacity than dataflash, and low cost too, but how well do they go?
> >
> > Anyone here with experience with both? I have quite a number of 64Mbit
> > dataflash chips on hand so it would make sense to use them, but I dont
> want
> > to compromise the design just because the parts are on the shelf.
> >
> > Thanks
> > Dean
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>
>
>
>  ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>


-- 
Kind Regards
Dean Claxton


[Non-text portions of this message have been removed]

--- In AVR-Chat@yahoogroups.com, Dean Claxton <deanclaxton@...> wrote:
>
> Ouch - thanks for that Mike - that may well tilt me away from SD. Do all the
> other card formats have similar licencing?

Licensing is for use of the logos.

You can have an SD card in your product.

Just don't use the SD logo on your packaging.

don

Hi Mike,

 

Interesting. I never knew about the SD licensing. I guess I need to do more
research next time.

 

The cost is actually $1000 per year which is not a lot if you sell loads of
products but those companies like myself who sell only a few per year or one
off bespoke designs, this could be a nail in the coffin so to speak. As
Kenny asked, I might have to consider looking for something that is non SD
based. 

 

I am going to see about signing the NDA and getting a copy of the
specification to see exactly what is licensed as I am unsure if you use a
non SD format storage method, that it will be outside the licensing
requirements. I am looking at using an SD card for internal storage. The
user has no access to it from the outside. It is simply installed to give
data storage and download is over Ethernet, USB Flash etc.

 

Thanks for the heads up.

 

Dave.

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Mike Payson
Sent: 02 February 2010 01:58
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Looking at doing a datalogger using an XMEGA part -
not sure which storage technology to use

 

  

If you're making a product for sale, be sure to read the license terms of
each technology before deploying. It's possible that you may decide that one
tech is better than the other for non-technical reasons. I'm not familiar
with Dataflash, but I can tell you that in order to include a SD card slot
in your product you are required to join the Secure Digital Association,
which costs a couple thousand dollars, and to pay annual license fees per
product, which are thousands more. It's been a while since I looked, but I
believe it was around $5000 for the first year and $2-3k for all future
years if you sell only one product. The price is regardless of whether you
sell one board or millions.

I suspect that you could make a small hobbyist board without having to worry
about the license fees, but it is something that you should be aware of.





[Non-text portions of this message have been removed]