ARM controller with integrated DAC

Hi everybody,
I am searching for a controller with a fast integrated DAC but haven't
been able to find anything suitable. Google led me to TIs AM3517 but
this is absolute overkill.
I need processing power but not much in terms of interfaces. Something
as simple as an LPC 2103 from NXP (albeit faster) with a DAC would be
perfect.
An ARM controller would be preferred but if necessary we consider
another platform.
I'd be grateful for any hint.
M'

On 16/08/2010 13:35, Michael Keith wrote:
> Hi everybody,
> I am searching for a controller with a fast integrated DAC but haven't
> been able to find anything suitable. Google led me to TIs AM3517 but
> this is absolute overkill.
> I need processing power but not much in terms of interfaces. Something
> as simple as an LPC 2103 from NXP (albeit faster) with a DAC would be
> perfect.
> An ARM controller would be preferred but if necessary we consider
> another platform.
> I'd be grateful for any hint.
> M'

Why do you want an integrated DAC?  There are not many microcontrollers 
with good DACs, while external serial DACs are easily available.  What 
are your requirements for the DAC - channels, resolution, speed, etc.?

"Michael Keith" <mjkeith@gmx.de> wrote in message 
news:er7i661s5pa2pobueaad9jc5rlpktmmghn@4ax.com...
> Hi everybody,
> I am searching for a controller with a fast integrated DAC but haven't
> been able to find anything suitable. Google led me to TIs AM3517 but
> this is absolute overkill.
> I need processing power but not much in terms of interfaces. Something
> as simple as an LPC 2103 from NXP (albeit faster) with a DAC would be
> perfect.
> An ARM controller would be preferred but if necessary we consider
> another platform.
> I'd be grateful for any hint.
> M'

ST offer ARM Cortex parts with integrated DACS - oddly they come on the 
STM32F100 series (the "value" range") and some of the STM32F103 
("performance" range) but not on the STM32f101 RANGE.

The 100 series parts are cheap and simple but may be hard to get for a 
little while because they are new introductions.

Michael Kellett

On Mon, 16 Aug 2010 13:35:44 +0200, Michael Keith wrote:

>
>
>Hi everybody,
>I am searching for a controller with a fast integrated DAC but haven't
>been able to find anything suitable. Google led me to TIs AM3517 but
>this is absolute overkill.
>I need processing power but not much in terms of interfaces. Something
>as simple as an LPC 2103 from NXP (albeit faster) with a DAC would be
>perfect.
>An ARM controller would be preferred but if necessary we consider
>another platform.
>I'd be grateful for any hint.
>M'

You may be able to use a PWM output but it will also drive extra components. 
I cannot remember an arm with PWM outputs but I am sure I have seen many 8051
core processors with a few PWM outputs.  This all depends on the specs you
need to meet for your dac output.

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 �s.
> 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'

Hi Nitro,
>You may be able to use a PWM output but it will also drive extra components. 
>I cannot remember an arm with PWM outputs but I am sure I have seen many 8051
>core processors with a few PWM outputs.  This all depends on the specs you
>need to meet for your dac output.
The first idea was "If the chip has a DAC, we're set."
See my response to David for some technical details.
Thanks for your comments.
M'

Hi Michael,
>ST offer ARM Cortex parts with integrated DACS - oddly they come on the 
>STM32F100 series (the "value" range") and some of the STM32F103 
>("performance" range) but not on the STM32f101 RANGE.
>
>The 100 series parts are cheap and simple but may be hard to get for a 
>little while because they are new introductions.
thanks for this info. Maybe they are faster than the DACs in the
LPC17XX series (which I found in the mean time), but probably not as
fast as needed.
Anyway worth a look.
Thanks again
M'

On 16/08/2010 15:51, Michael Keith 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 �s.
>> 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).
>

You can't easily get a data rate of 10 MHz out of a micro controller. 
You will need to have some sort of FIFO or buffer, probably using DMA 
for efficient transfers.  If you can find an ARM with a programmable 
queued SPI interface and DMA support, then you might get it running well 
enough using that (with a fast SPI DAC, obviously).  Alternatively you 
might be able to use DMA triggered by a timer and writing to an external 
bus with a parallel bus DAC.

You might also want to look into using programmable logic.

What is the data source?  Are you just replaying samples from memory, or 
are you calculating them at this rate?  And are you able to 
pre-calculate and buffer up the samples?


> 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.
>

It doesn't really matter too much how they work internally - it's just a 
matter of getting a DAC with the interface and specs that suit you.  10 
MHz is not really high speed for DACs (look at TI's web site for 
examples), but it is high enough that you need to think carefully about 
how you are going to move the data around.

In comp.arch.embedded,
Michael Keith <mjkeith@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 &#4294967295;s.
>> 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.

If low resolution, low precision and noise are not a problem: Use that R-2R
ladder memory and connect it to 5 outputs. :-)
Update rate is limited only by your I/O speed (which me not be as high as
you would expect on some controllers).

-- 
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

"One Architecture, One OS" also translates as "One Egg, One Basket".

Nitro wrote:
> On Mon, 16 Aug 2010 13:35:44 +0200, Michael Keith wrote:
> 
>>
>> Hi everybody,
>> I am searching for a controller with a fast integrated DAC but haven't
>> been able to find anything suitable. Google led me to TIs AM3517 but
>> this is absolute overkill.
>> I need processing power but not much in terms of interfaces. Something
>> as simple as an LPC 2103 from NXP (albeit faster) with a DAC would be
>> perfect.
>> An ARM controller would be preferred but if necessary we consider
>> another platform.
>> I'd be grateful for any hint.
>> M'
> 
> You may be able to use a PWM output but it will also drive extra components. 
> I cannot remember an arm with PWM outputs but I am sure I have seen many 8051
> core processors with a few PWM outputs.  This all depends on the specs you
> need to meet for your dac output.
> 
> 
elsewhere, OP said 100nS and 5 bits -> 3nS resolution in the PWM. I 
don't know of any parts like that.
Bob