[hpsdr] Questions re: FPGA firmware

[Joe Martin K5SO]

Hi John, 

To add to Alex's response here are a few additional comments: 

1) It isn't clear at this point what the max number of receivers will be in view of the other features that must also be a part of the code.  Certainly users are free to use whatever version of firmware they wish and are not limited to the officially released or current official HSPDR version(s) whatever that/those may be.  

2)  The initial (production) version of the Hermes firmware (Hermes v1.8) incorporates the latest automatic/manual Alex filter switching and VNA support.  It was found that implementing more than 2 receivers with the new additional code seemed to cause some (unexpected) intermittent switching errors to sporadically occur with regard to Alex filter switching in particular so in order not to slow the testing/production of the Hermes boards it was decided to provide the boards initially with 2 receivers implemented in the initial firmware release with the idea that more receivers will be made available when those and/or any other switching issues are sorted out and fixed. 

3) FPGA space and FPGA performance both, I think.  It has been observed that when running with 100% loading of the FPGA (i.e., using 100% of the logic resources) can under some circumstances lead to timing problems and erratic behavior so care must be taken and careful testing must be performed when using heavy FPGA loading.  Hermes v1.8 uses 67% of the logic resources and so avoids the issues sometimes observed with heavy FPGA loading.

4) Yes.  Phil had intended to post the Hermes source code to the SVN when the Hermes units shipped.  I will be happy to send to you directly/immediately the source code for Hermes v1.8 if you wish as I think Phil has been swamped with work lately and hasn't gotten to the SVN uploading task yet and may at the moment be taking a well-deserved/needed holiday away from home for the next week or two. 

5) Yes.  Hermes v1.8 was built using the free web version of Quartus II v11.1 sp2.  

73,  Joe K5SO

On Oct 30, 2012, at 2:36 AM, John Marvin wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> I have a few questions regarding Hermes FPGA firmware:
> 
> 1) I know that some work is being done to support 7 receivers in Hermes. Will that support be part of the standard firmware, or will it only be available as a special version?
> 
> 2) I noticed at one time support for 4 receivers was added to the Mercury, but then it appears that was backed out to 2 receivers. Was that done because there were problems/bugs with the 4 receiver version, or was it due to the space required (I saw a comment saying that with the 4 receiver version the FPGA was 98% full)?
> 
> 3) What is the limiting factor on the number of receivers supported (i.e. FPGA space, FPGA performance, etc.)?
> 
> 4) Will the source for the Hermes FPGA firmware be made available some time in the future?
> 
> 5) Can the firmware be built with the free web version of the Altera software, or is another version required?
> 
> Thanks!
> 
> John
> AC0ZG
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