> looks like an ARM is a good fit then.


 Yes, if you can live with whatever speed results.
ie if DMA works ok for Size/Data rate.

 5 Bits is ok from processor ports, tho you could add a Logic buffer
device, if you want less Vcc noise.

 A second step would be a 2nd chip, for the DAC-handling.

 That could be either a separate processor, or you could use a small
CPLD, to push your 5bit port rate to a 16bit port Mux'd 3 ways, and
treble your workable DAC speed.

-jg

Hi Hamilton,
>> On Aug 18, 8:18 am, Michael Keith<mjke...@gmx.de>  wrote:
>>>
>>> we didn't consider an FPGA. Our intention was to use an ARM (or a
>>> similar processor).
>>> Reason 1: familiarity
>>> Reason 2: price tag $1 - $2
>
>
>The OPs goals are not possible.
with a small ARM things look quite promising.
M'

>You can get a small CPLD (need milk^H^H^Hemory) for $1, couple with an
>external sram (free).  You can pull sram chip out of any old
>motherboard (or module).  Add an op-amp for 50 cents and you can build
>the whole thing below $2.
Hi,
looks like an ARM is a good fit then.
Thanks
M'

>> Hi Leon,>If you need a really fast DAC, simply interface one to an XMOS chip:
>>
>> >http://www.xmos.com
>>
>> >Development will be much easier than if you used an FPGA. You could
>>
>> we didn't consider an FPGA. Our intention was to use an ARM (or a
>> similar processor).
>> Reason 1: familiarity
>> Reason 2: price tag $1 - $2
>> While we could waive reason 1 it would only make sense if it offers a
>> significant advantage for reason 2: arrive at a price tag below $2 at
>> 1k units. I would be surprised if there are any chips (FPGAs or XMOS
>> or ???) which meet this requirement, but then this domain is a foreign
>> one for me.
>>
>> Anybody knows if there are chips in this price range? Our requirements
>> wrt gate count are probably rather low, given what is possible in
>> modern hardware. (I know that 'rather low' is vague, but as I said we
>> originally didn't consider it and it is foreign territory.)
>>
>> Thanks for your feedback
>> M'
>
>The cheapest XMOS chip is $4.92 for 5000+. You might not be able to
>find anything that will do what you want for the price you quoted.
Well, looks like there is no reason to not use an ARM.
Thanks
M'

On Aug 18, 9:43=A0am, hamilton <hamil...@nothere.com> wrote:
> > On Aug 18, 8:18 am, Michael Keith<mjke...@gmx.de> =A0wrote:
>
> >> we didn't consider an FPGA. Our intention was to use an ARM (or a
> >> similar processor).
> >> Reason 1: familiarity
> >> Reason 2: price tag $1 - $2
>
> The OPs goals are not possible.

Part only for CPLD is reasonable, FPGA is not.

> On Aug 18, 8:18 am, Michael Keith<mjke...@gmx.de>  wrote:
>>
>> we didn't consider an FPGA. Our intention was to use an ARM (or a
>> similar processor).
>> Reason 1: familiarity
>> Reason 2: price tag $1 - $2


The OPs goals are not possible.

As a professed software guy, he does not understand the hardware 
requirements to do the task.

Or he has wishful thinking as most software people do.

My $.02

hamilton

On Aug 18, 8:18=A0am, Michael Keith <mjke...@gmx.de> wrote:
> Hi Leon,>If you need a really fast DAC, simply interface one to an XMOS c=
hip:
>
> >http://www.xmos.com
>
> >Development will be much easier than if you used an FPGA. You could
>
> we didn't consider an FPGA. Our intention was to use an ARM (or a
> similar processor).
> Reason 1: familiarity
> Reason 2: price tag $1 - $2
> While we could waive reason 1 it would only make sense if it offers a
> significant advantage for reason 2: arrive at a price tag below $2 at
> 1k units. I would be surprised if there are any chips (FPGAs or XMOS
> or ???) which meet this requirement, but then this domain is a foreign
> one for me.
>
> Anybody knows if there are chips in this price range? Our requirements
> wrt gate count are probably rather low, given what is possible in
> modern hardware. (I know that 'rather low' is vague, but as I said we
> originally didn't consider it and it is foreign territory.)

You can get a small CPLD (need milk^H^H^Hemory) for $1, couple with an
external sram (free).  You can pull sram chip out of any old
motherboard (or module).  Add an op-amp for 50 cents and you can build
the whole thing below $2.

On 18 Aug, 16:18, Michael Keith <mjke...@gmx.de> wrote:
> Hi Leon,>If you need a really fast DAC, simply interface one to an XMOS chip:
>
> >http://www.xmos.com
>
> >Development will be much easier than if you used an FPGA. You could
>
> we didn't consider an FPGA. Our intention was to use an ARM (or a
> similar processor).
> Reason 1: familiarity
> Reason 2: price tag $1 - $2
> While we could waive reason 1 it would only make sense if it offers a
> significant advantage for reason 2: arrive at a price tag below $2 at
> 1k units. I would be surprised if there are any chips (FPGAs or XMOS
> or ???) which meet this requirement, but then this domain is a foreign
> one for me.
>
> Anybody knows if there are chips in this price range? Our requirements
> wrt gate count are probably rather low, given what is possible in
> modern hardware. (I know that 'rather low' is vague, but as I said we
> originally didn't consider it and it is foreign territory.)
>
> Thanks for your feedback
> M'

The cheapest XMOS chip is $4.92 for 5000+. You might not be able to
find anything that will do what you want for the price you quoted.

Hi Leon,
>If you need a really fast DAC, simply interface one to an XMOS chip:
>
>http://www.xmos.com
>
>Development will be much easier than if you used an FPGA. You could
we didn't consider an FPGA. Our intention was to use an ARM (or a
similar processor).
Reason 1: familiarity
Reason 2: price tag $1 - $2
While we could waive reason 1 it would only make sense if it offers a
significant advantage for reason 2: arrive at a price tag below $2 at
1k units. I would be surprised if there are any chips (FPGAs or XMOS
or ???) which meet this requirement, but then this domain is a foreign
one for me.

Anybody knows if there are chips in this price range? Our requirements
wrt gate count are probably rather low, given what is possible in
modern hardware. (I know that 'rather low' is vague, but as I said we
originally didn't consider it and it is foreign territory.)

Thanks for your feedback
M'

On 16 Aug, 14:51, Michael Keith <mjke...@gmx.de> wrote:
> Hi David,
> thanks for your comments.>Why do you want an integrated DAC?
>
> well, as a first idea it seemed like a nice feature.
> Meanwhile I found that the (rather new) LPC1765/66/68 come with a DAC.
>
> Don't laugh - I am a software guy, not an EE and was just tasked to
> evaluate a new idea of my boss. Turns out the DAC in the ARM is too
> slow: It has a maximal conversion rate of 1 =B5s.> What
> >are your requirements for the DAC - channels, resolution, speed, etc.?
>
> Bad news: We will produce data at the rate of 200 ns (and maybe even
> down to 100 ns).
> (Hopefully) good news: We only need a very low resolution, 5 bit will
> be sufficient (and we need only one channel).
>
> My knowledge of analog conversion is limited to
> - DACs exist and
> - (from very long ago) a faint memory of R-2R-networks.
> Any link to information on how to perform D/A conversion at the rate
> mentioned above would be welcome. I could hand it over to an EE
> colleage to understand the technical details.
>
> Thanks
> M'

If you need a really fast DAC, simply interface one to an XMOS chip:

http://www.xmos.com

Development will be much easier than if you used an FPGA. You could
buy one of these Sparkfun boards and XTAG2 for $100 and add a DAC to
it:

http://www.sparkfun.com/commerce/product_info.php?products_id=3D9428