[hpsdr] My $0.02 worth on board size...

[Mike Niswonger]

       Well, I've been lurking for a while, but it seems that a subject 
has arisen that I just had to come out of hiding for (and I may get a 
little scorched in the process)...

        I started to respond to Alex's original  a few days ago, but I 
decided to kick things around and think them through before responding.  
My first impression a few weeks ago of the 100mm x 100mm format was that 
it was a little on the small side.  I'm used to VME sized 6U x 160mm 
boards (200mm x 160mm).  I have used VME 3U x 160mm (100mm x 160mm), but 
was not happy with the layout because of the lack of stiffness on the 
board (the DIN connector is on the 100mm side).  I originally thought 
that Alex was proposing something along this line - with the DIN 
connector still on the 100mm edge of the 100mm x 185mm format.

       However, after looking at his proposed layout which puts the DIN 
connector offset on the long (185mm) side, I/O connectors mounted on the 
near 100mm side (with PC style "stakes" optional) and the option of 
additional internal buses, I'm suitably impressed.  A great idea! Or I 
thought so - apparently not everyone agrees...

       To my knowledge, only the Atlas has been fabbed, with Janus soon 
to follow.  Before we lock the format down for future boards, we now 
have the option of giving designers flexibility in the board size that 
they design; over double the working area it they need it and still 
compatible with smaller 100mm deep boards.   The worst case rework on 
any board that has already been laid out will be moving the I/O 
connectors from the edge opposite the DIN connector to the adjacent 
edge.  Since I'm not designing the boards, I'd like to hear some 
discussion from the designers on how greatly it would affect them.  
While it might be a little painful right now, wouldn't it be worth it 
for the added future flexibility?

       From the users that object (especially Chris, since he seems to 
be the most vocal),  can I ask why - if you don't use a "large" PC 
chassis but a custom chassis, that reorienting the connectors will make 
this project totally unsuitable for your purposes?   I'm sorry Chris, 
but that's often how your threads come across.  To me, the proposed 
ninety degree offset makes far more sense - is there something that I'm 
missing?  By sticking with your preferred 100x100 fixed format we 
unrealistically  limit the design of the HPSDR board family before it 
even gets off the ground.
   
       Remember that one of the primary guidelines behind this project 
is "openness".  Please, let's use a little engineering forethought to 
really keep the system open to maximize the usage of boards - of ANY 
size - without having to go though board redesigns.  I'd like to be able 
to mix and match 100x100, 100x160/185 or 125x185 boards.  We don't have 
that option with the 100x100 board with the I/O opposite the DIN 
connector.  Forget the PC case - it's a red herring, and not the real 
crux of the discussion.

       Let the rock throwing begin...

       Mike Niswonger, W4CMN