Re: Open-Source Spectrometer

On Wed, Nov 16, 2011 at 2:33 PM, John Griessen <john@industromatic.com> wrote:
> On 11/16/2011 12:10 PM, Cathal Garvey wrote:
>>
>> Wouldn't that
>> mean your "job" would then be to create a "shield"
>
> Your job as product developer is to deliver more bang per buck, so the
> $89 price of  a Beagle Bone is hard to resell for cheap.  And
> Teensy ardino compatibles are better to design on top of than
> straight "shield" versions with their large connectors and large
> size and large price for newbies.
>
> On 11/16/2011 12:17 PM, Nathan McCorkle wrote:
>> What's the cheapest embedded linux board that's out there that can
>> bring over the 1MB/s from a 2nd micro?
>
> There's more to consider.  Why not have the first micro reduce the data some
> also? 1MB/s is raw, very raw.  A little filtering by the first micro
> would let you have a cheap flat pack leaded linux running micro instead
> of the all out ones you like.  Likewise with the Wifi.. 1MB/s is letting
> your lab instrument do nothing but send raw data...  If you reduce
> it reasonably, you still have plenty of room for outside re-analysis.

In my experience no science compresses their data, except for CERN
maybe... I'm not sure a slow micro could handle a compression scheme
though. Something linux-based could though.

>
> Having the first processor be a python-on-a-chip one would let users
> easily change the filtering routines and access raw data as well.
>

I don't like the sound of python on a chip for more than a learning
tool, but my friend said there was a microfluidic controller that had
lots of MUXed pins for valving that ran with a python-on-a-chip
chip... he did say it didn't go anywhere, can't say it was because of
the chip though :)

> There's just not going to be much interest in the world for the CCD raw data
> though,
> so why send it out?  Making an open way to access it as it flies by inside
> the machine
> is better.
>
> The electronics bill of materials should be $20-$30 for two processors,
> one running linux, and USB ports, not including the CCD.
>

Ok, TI launchpad is $4.30, has SPI, master clock at 16Mhz with
62.5ns/instruction. Arduino 16Mhz (not sure on timings, probably
similar)... both compile with GCC (this is a feature that I'd like to
preserve no matter what platform) and are coded in C, can optimize
with assembly if needed... Launchpad is cheaper really because its
subsidized by TI

Link one of those uCs to the CCD, link the CCD out to the nice ADC
with SPI out, link the SPI out to this FTDI SPI-USB virtual com port
chip (FT232H, USB 2.0, win, linux, mac drivers, $4.3), link that to
whatever system you want.
http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=123533426

Just found this via the Arduino wikipedia page, near the bottom...
this ($35 100Mhz ARM) or the $5-cheaper 60Mhz might run linux (uClinux
comes to mind) and a web server, then attach the CCD subsystem and
comms dongle via USB.

> John
>

--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics

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