While I wait for parts to arrive tomorrow and take a break form the display board creation which is mechanically more complicated that I anticipated, I have been running the overall design of D-DAQ through my head.

The displays are hooked up via SPI. Normally you need CLK, MOSI, MISO, SS pins for SPI. The SEPS525 requires the MISO pin to stay unconnected when using SPI so I'm using that line for a button's input. I then noted some language in the datasheet about the 2 different SPI modes, normal and framed.

Normal SPI mode will only generate a CLK when the interface is active and need to send data. Framed always generates a CLK and uses the SS pin to send a 1 CLK pulse to indicate a transfer is about to occur. I missed the detail saying that in Normal mode, the SS pin is optional.

I ended up tying all three SS pins to ground as required by the data sheet, and ended up scrounging around the board to find 3 pins for toggling the RS pin on the SEPS525 to differentiate from a command and data. Oops.

The good news is that I have 3 extra pins to play with if the need arises. The bad news is that I'm running unnecessary pins to control functionality. Boards of proto 2 have not been ordered yet so I'll probably fix this in the near future.