[hpsdr] Hermes

[Jeremy McDermond]

Considering that Hermes is supposed to be after Alex on TAPR's production schedule, there's plenty of time to roll a few more beta boards with ethernet... (sorry Scotty) :p

My major concern with moving to ethernet is that it's currently largely unproven.  We don't know what the tradeoffs of such an architecture are going to be.  Maybe I have the wrong impression but the Atlas bus based rigs are positioned as further on the "experimenters" scale than Hermes.  It might be nice to test the ethernet architecture on Atlas based rigs before moving it to the more integrated Hermes.

Another thing to consider is the usage case.  I'm very interested in Hermes for use with my laptop.  Making it Ethernet complicates that a bit because if I want to connect both to the internet and to Hermes, I now have to carry a hub/switch in my laptop bag because my laptop only has a single Ethernet.  It's not a huge deal, but USB connectivity plugs into one of many ports on my laptop.  Something to think about.

On Aug 4, 2010, at 7:06 PM, Phil Harman wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> All,
> 
> Having completed the Beta testing of Hermes we are now preparing to make
> the necessary changes to bring the board into a production ready state.
> 
> There are quite a few changes which are mainly due to the fact we want to
> ensure the product lives up to the 'High Performance' name tag.
> 
> One of the changes is to replace one of the high current linear regulators
> with a SMPSU. We are fortunate to have Kjell, LA2NI,  on our design team.
> Kjell has designed a high frequency SMPSU that works well when
> incorporated on the Hermes PCB and does not introduce significant spurs. 
> This substantially reduces the current drain and also the heat
> dissipation.
> 
> The other potential change is this.  I have this week build a prototype
> OzyII Gigabit Ethernet board. It works very well and I'm impressed with
> how rugged Ethernet appears to be in comparison to USB and Firewire.
> 
> We therefore have the opportunity to replace the USB interface on Hermes
> with Ethernet.  There are a number of advantages in doing this:
> 
> - we overcome the USB driver issues when using different operating systems
> - we can 'network attach' Hermes
> - we will have a very high speed interface to the board for future features
> - we can use a much longer Ethernet cable than USB allows
> 
> the disadvantages
> 
> - it may need more that one spin of the PCB which will delay the delivery
> - we will use approximately 10% of the FPGA to implement the Ethernet
> interface.
> 
> I'm not too concerned about using more of the FPGA since the device we are
> using is 70% larger than that used on Mercury.
> 
> So "to USB or not to USB - that is the question"?
> 
> 73's Phil...VK6APH
> 
> 
> 
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--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj at xenotropic.com




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