[time-nuts] Controlling FEI 5680A

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jan 15 10:45:56 EST 2012

On 01/15/2012 05:48 AM, Chris Albertson wrote:
> On Sat, Jan 14, 2012 at 4:32 AM,<EWKehren at aol.com>  wrote:
>> I have no expertise when it comes to filter design or programming PIC's or
>> other micro controllers. But I know what works for me. For 11 years I have
>> been  using Shera controllers with very good results. (I still have some new
>> assembled  extra A&A boards, if any one is interested, please contact me
>> off list) Over  the years I have made hardware work around's and made my own
>> boards ending up  with 120 and 240 samples and 100 MHz clock in stead of 24
>> MHz. Over time chips  are harder to get. The solution is an Altera MAX 3000
>> gate array and that input  circuit can be implemented on a $ 2  100 MHz
>> version or $ 5   200  MHz version using either a 100 MHz or 200 MHz clock. That
>> circuit works with the  present Shera PIC but that is a 28 pin $ 4   device.
>> Since in  this application the controller does not have  to be all things
>> for all  devices it would make sense to use a PIC16F688  or any other 14 pin
>> device.
> Have you thought about putting the PIC  _INSIDE_ the Altera FPGA?
> It's a common trick to implement a microcontroller in the FPGA and you
> can get the code for just about any CPU core online.  Here is an
> example of "virtual PIC":
> http://www.embeddedtronics.com/pic_core.html
> If the PIC fits inside then that is one less chip on the PCB.   The
> example above found that could run the virtual PIC a little faster
> than a real pic so you don't give up any performance

A short notice on embedded CPU/MPUs into FPGAs. Using PIC or AVR might 
be tempting, but I consider any clone "dirty" from a rights perspective, 
MIPS for instance have been very protective on their side, so has ARM. 
So far has the SPARC been the only big one being accepted in their 
LEON-x variants that I know of. We be sad to see the cotton industry 
level being smashed by the big firm lawyers.

So, either using the OpenRISC variants or similar. There is loads of 
CPUs on the OpenCores website, but just because they are there do not 
think they are free to use if they are clones of commercial stuff.

I would either use one of the FPGA vendors CPUs and then write the core 
in C, or use a free CPU.

I could also roll my own CPU, as I have already done before, but 
building a tool-chain including GCC is a bit of home-work. For my 
application I haven't bothered, but it is tempting to get C capabilities.

Then again, if someone could show that the PIC and/or AVR is free to 
clone in FGPA, by showing a clear statement from the respective 
technology holders, then that would be a way forward.

I've done this analysis before, and so far I have not seen any 
comprehensive open analysis covering these aspects.

I fear that this is way off topic for this list, so I propose that this 
aspects is continued on another list, such as the FPGA-Synth list, which 
faces essentially the same problems.


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