I am doing a little re-arrangiing, wiring the top SD & uSD in parallel, adding a 2nd SD to the bottom & wiring it in parallel to the bottom SD.
Each side will have its own chip select, which is seperate from the shield slave select.
-what I generally miss are the pullups on the sdcards pins like CS, datain,..
The 2 chip selects have 10K pullups to Vcc33 for the SPI signal buffer chip. I am not putting any additional load on the MISO, MOSI, and SCK lines.
-pullups on the carddetect, writeprotected..,..
Will rely on the internal pullups for that. It is just a switch closure, no active signal behind it.
-add the sense (carddetect) on the microsd as well (and the pullup),..
I have removed the WP signal and instead used A6 and A7 as the top and bottom card detect/sense
I have read (perhaps prior Skyjumper posts?) that reading that the software can write the card even if it selected.
-add pullups on any RX, RX1 and alike lines which may float when the cable is not connected,..
I don't see the need for that. If your cable is not there, you will not get good data anyway. And then its just exrta load when you want to use that pin with a shield.
-I would not use A7 for WP of sdcard1 but for cardetect (sense) of the usdcard,..
-try to load the power supplies with a few hundred mAps (when applicable) and see if it works stable (when inserting sdcards, when formating sdcards, etc),..
3.3V Reg is good fror 400mA, not worried about that one.
- I would add few 10-20uF ceramic caps to the sdcards vcc33,..
Alread has a 100uF cap on the input, 100nF on the output, and 100nF at the buffer chip
PS2: did you ever put a shield into this Mother of all boards? ,..
Haven't used it with one (I don't have any) but we used a adafruit shield to hold the header pins in place, so alignment is correct.
I also used Blink to toggle all outputs, leading to the revised pins_arduino.c for this board.
If I were you I would assemble one more board and ask somebody to use it intensively for 1-2weeks in some harsh environment (various shields etc.). Then I would consider the second batch.. Moreover, you planned only one sdcard, did'n you?,..
Am assembling 8 or 9 more tomorrow, will then have some to play with besides the 2 I built to start for debugging.
They will not have the uSD shield. Rev 18 boards will have that option.