Good evening,
I thought some more about how going to two boards might work layout-wise.
My first thought was that it would be very undesirable to go to two boards,
as we take up stack space which could be allocated to other experiments.
With conservative planning on the flight board and some work to limit
excess components on the current design, I think it's entirely possible to
fit the flight model on one board.
Looking at the board space we have available (~26 in^2) and the current
schematic, there would be several steps I would take before going to
another board. First, we have a lot of bottom board space which isn't used
at all. Pullup resistors on the digital side, power supplies, and even the
CPU could be placed on the bottom of the board. Just by removing the UFL
connectors and replacing the 0603 components with 0402s, we'd save around
an inch for practically nothing. Additionally, more layers on the board may
allow greater route density on the top and bottom layers. I think that 8 or
10 at maximum will be sufficient and provide a shorter path than a second
board would allow. I made an *approximate *placement diagram which shows
the current configuration and possibilities for the new board.
I'm not opposed to multiple boards for development purposes. We could break
all the circuits out onto different test platforms which could be
distributed to more people for software development. We could troubleshoot
each section individually before combining onto the flight model. I think
for the best performance on the flight model, it should be a single board.
Something Bill pointed out in the meeting was that heat dissipation might
become an issue with so many components packed onto the board. While the
board can do a lot to sink heat, perhaps additional sinking will be
necessary. On the RT-IHU, we plan to create a heat spreader which presses a
ceramic block onto the TMS570. Originally, this was going to also have
milled cavities to act as shielding for the components, but the design was
shrunk for unknown reasons (something that Bob Davis had been working on).
Perhaps something like this might be beneficial, although it would be
expensive and add weight and height. Just a thought.
This is my point of view from the layout side. While a challenge, I
definitely think a single board is possible. Thoughts?
Thanks,
Cameron
-------------------------------------------------
Cameron Castillo
KJ7ILB
*P*: (503) 752-8877
--------------------------------------------------
