I just got my hands on a brand spanking new C4 BB a few days ago. I am
trying to make a daughter board
with peripherals. So I need to know the mounting hole size and
location. I looked through the BBSRM
pdf document. Even though it has the images of the board (the layers
of PCBs). It is still not clear there
the mounting holes, and relative location of the expansion header
How to finger out the mounting hole locations, size and relative
position of the 28 pin expansion header?
The pin 26 on the expansion is nRESET. I suppose it is an Output from
BB to reset circuits on the daughter
board. Is it true? The manual has it as
"The nRESET signal is the main board reset signal. When the board
powers up, this signal will act as an input to reset circuitry on the
expansion board. After power up, a system reset can be generated by
the expansion board by taking this signal low. This signal is a 1.8V
It seems also that the daughter board can use it to reset beagleboard?
All of this information is provided in the form of Gerber files and Allegro CAD files. There is a free PCB viewer that you can download from Cadence that will let you read the file. When it comes up, there is a whole chart that tells you the size of all of the holes on the board. You can also use the measuring feature of the tool, and get the location and spacing of the mounting holes.
Reset line is an input and and output. It is a tri-stated line that is driven by the TPS65950 via a tristate buffer. If you were to ground it at the expansion header, it will reset the board.
I am not aware of any ‘mounting holes’ (as in to hold the connectors, not the berg holes, which are of 0.1" pitch) for Beagle expansion. Also, the LCD connectors have a 0.05" pitch. You can either use the gerber files as suggested by Garald (that gives you the most accurate data), or for a quick check, you can use the Google Sketchup file of the Beagle board and measure the distances yourself (but remember, it might be prone to marginal error if you don’t do it 100% right).
The mounting holes are the big holes on each corner of the board.