[hpsdr] Call for Comments and Discussion - OzyII

[Eric Blossom]

On Tue, Jul 21, 2009 at 08:05:19PM +0100, Bob Cowdery wrote:
> Eric Blossom wrote:
>> On Tue, Jul 21, 2009 at 12:29:20PM +0100, Bob Cowdery wrote:
>>   
>>> "I'd say UDP is the way to go. Not only is UDP almost trivial to   
>>> implement into an FPGA once you have raw Ethernet TX/RX working, its  
>>> functionality is easily sufficient for modern HDR systems. Datagram 
>>> loss  is not an issue when streaming over a (dedicated) local net, 
>>> and a host  that can't keep up with an UDP flow will certainly choke 
>>> on the same  flow over TCP."
>>>
>>> This seems to be a pragmatic proven option but doesn't add huge value 
>>>  over OZY1 except cable length and multicast. These two alone may be  
>>> sufficient justification.
>>>     
>>
>> With gigabit ethernet and jumbo frames it's possible to transfer
>> 120MB/s to/from the host.  That about 4x what you can do with USB
>> _and_ it's full duplex.  (When you start sending 120MB/s to/from the
>> host you'll find you have a whole new set of problems ;-))
>>
>> Eric
>>   
> That may be so, but is it a requirement to have such a data rate. Could  
> you use it in any sensible way. Could you run multiple Mercury cards for  
> example.

With the current board stack there's pretty much no way to generate
this much data given the low rate of the interconnect.  If the ADC,
FPGA, and gigE are all on the same card, it starts to make sense.

Eric

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