Re: Simple multi-channel serial ADC (8-ch)?
- From: "linnix" <me@xxxxxxxxxxxxxxxxxx>
- Date: 15 Feb 2007 11:26:24 -0800
On Feb 15, 10:16 am, Joerg <notthisjoerg...@xxxxxxxxxxxxxxxxxxxxx>
wrote:
linnix wrote:
On Feb 15, 8:52 am, Joerg <notthisjoerg...@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Rene Tschaggelar wrote:
Joerg wrote:
Hello Folks,
As an analog guy I get goose pimples when I see converters like the
TLV1508. Impressive performance but, boy, do they need a complicated
liturgy to get data out of them. Many of them must be told via SPI
that I want to read this, that and the other value. Then you must
patiently wait x clock cycles, wasting away bus time. The guy who
designs the host processing will throw his coffee mug at me because
there'll be a dozen of these.
Here is what I am looking for: 10 bits or so, 8 channels, bone-simple
readout, can very very slow, low kHz range. All I need is to read DC
values and it doesn't matter when the exact sampling time was. SPI,
I2C, anything serial works. I mean, with a FIFO in there they should
be able to do continuous autoscan and just dump the last valid set of
values upon request.
Any ideas? I am also looking for 10-12 bit DAC with lots of channels
but that seems to be much simpler.
Joerg,
I'd employ a controller such as the AVR Tiny26 with 8
differential or 11 single ended 10 bit channels.
Since you need a dozend of them just hook them together
with an SPI or an USI.
I wanted to avoid a uC on there because it wouldn't be needed for any
other purpose.
Micros are sometimes cheaper than standalone ADCs.
You don't need to use them for anything else.
But they need to be flash programmed and are still more noisy.
They are too slow for the analog stuff I am doing on the
boards.
How fast do you need?
Is 500KSPS too slow for you?
How about 1MSPS?
The ADC can be slow, a few kHz at the most. Not critical. What I meant
is that I can't use a uC for any of the control gear tasks. That would
have justified the hassle of in circuit programming. Unless you buy gang
programmers many manufacturers do not offer file dumps. They give you a
nice and cozy design environment but, for example, TI does not offer a
feature where you connect an EZ430 pod or the like and just download a
file right from the OS or from a web browser. You have to do that from
the IAR console. Not such a good thing in this case since the engineers
at my client are all specialized in optics and process control.
Yes, I understand your concern. Programming environment is one reason
I am avoiding the MSP. At least with ARM, JTAG is possible. For our
particular project, we need to be able to JTAG one micro from another.
If flash is reliable, then I would not care about the programming
part.
I am not scared by the initial programming, but the possiblity of
re-programming in the field makes me nervous.
For example, flash is very likely the problem for the AT91Sam7S256
failing in the field. Failure is Failure, even if you can re-program
it.
.
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