I've used FreeRTOS for a couple of robotics projects. Quite nice and
not too hard to get into as far as real time operating systems go.
An RTOS comes into it's own when you have a lot of very time-sensitive
tasks to take care of. For instance, keeping a servo motor at a given
position requires a very short pulse at very precisely defined
intervals. When you are trying to control a half dozen of these, while
also reading a bunch of sensors, you can no longer easily do this in a
single control loop - you need an RTOS.
But it's an added layer of complexity that may not be warranted in the
spectrophotometer project.
You can do more for less money with some other alternatives, but I
like the ATMEL chips and the Arduino IDE for ease of use for novices.
To make a good user-hackable device it still seems a decent choice to
me. In the end, I suspect your lighting and optics drive your overall
price more than does a few dollars in the processor choice.
Just a random opinion...
--Derek
On Jan 1, 1:10 am, Nathan McCorkle <nmz...@gmail.com> wrote:
> On Thu, Dec 29, 2011 at 10:00 PM, Jonathan Cline <jncl...@gmail.com> wrote:
> > On Dec 14, 1:59 am, Nathan McCorkle <nmz...@gmail.com> wrote:
>
> >> Arduino IDE
>
> > It is important in an OSS community to learn from previous projects.
> > OpenPCR for example chose Arduino (I suggested PIC or etc)
> > and I believe they learned the hard way that the Atmel parts
> > are not a good fit and Arduino costs more with fewer peripherals.
>
> Josh and Tito, Cathal... do you guys really think the Atmel chips
> aren't a good fit?
>
> the openSpectrometer team had thought that Arduino IDE would make it
> painless to begin tinkering with... or even just doing firmware
> upgrades.
>
> > Get their opinion on the project to see if they might have chosen
> > differently.
> > Recently I got an STM32 board from ST which is $15 and incredibly
> > functional; it includes all the firmware drivers needed and
>
> Sounds good, actually, but how easy is it to start programming it (I
> mean from the time you get it in the mail, setting up the software,
> and finally flashing it)?
>
> I think I can get away with using Atmel chips... but if the
> STM32F4DISCOVERY board is here to stay at $16 USD, it would probably
> be worth using if its easy enough for other hackers to get into.
>
> > hardware support for built in peripherals. No external
> > FTDI USB bridge chip would be needed. Check out
> > STM32-comStick or STM32F4DISCOVERY. Probably this
> > choice boils down to resolution on the A/D. STM32 is 12 bit.
> > STM32 uses FreeRTOS for it's framework. It's sufficient
> > though not very professional.
>
> What does FreeRTOS bring over using a C-style single threaded program
> ala Arduino or less complex micros?
>
>
>
>
>
>
>
>
>
> > Another option is the PIC32 UBW32 board which has excellent
> > USB support as well and all onboard peripherals. Hands down,
> > Microchip wins for the best free C compiler and IDE. Also
> > choice boils down to resolution on the A/D.
> > You may not need 16 bit. Do the calculation.
> > Pick the hardware with the best fit and function. The days
> > of needing Arduino because only those boards are available
> > are over - there are now very usable boards from each
> > microcontroller vendor - and usually cheaper than Arduino
> > considering the full system cost.
> > Cost is everything. Trim cost out of every corner of the
> > design. Running linux means increasing the cost by at least
> > 30% - typically it requires twice the amount of RAM and
> > code space compared to RTOS (yes, GNU libs are fat cows).
>
> > External SPI RAM will be slow and perhaps noisy, if you
> > need to add that. This could interfere with validity of the
> > data. Something to consider. Better to get a chip with
> > proper internal memory size.
>
> > ## Jonathan Cline
> > ## jcl...@ieee.org
> > ## Mobile: +1-805-617-0223
> > ########################
>
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> --
> Nathan McCorkle
> Rochester Institute of Technology
> College of Science, Biotechnology/Bioinformatics
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