CD -> NC
DO -> TXI (CH1) on LV side -> from TXO (CH1) on HV side to MISO on Uno
GND -> GND
SCK -> RXO (CH1) on LV side -> from RXI (CH1) on HV side to SCK on Uno
VCC -> 3.3V on Uno
DI -> RXO (CH2) on LV side -> from RXI (CH2) on HV side to MOSI on Uno
CS -> TXI (CH2) on LV side -> from RXO (CH2) on HV side to pin 4 on Uno
Not sure I needed to pass the chipSelect and SCK pins through the lever converter but hey, it couldn't hurt. I did also try it by connecting those two directly to the Uno.
The level converter is powered on the LV side with 3.3V and on the HV side with 5V. And a common GND with 5V (and the Uno.)
The sketch I'm using is the CardInfo sample. It correctly sets the chipSelect to pin 4. When I open the serial monitor, I get this:
Initializing SD card...Wiring is correct and a card is present. Card type: SD2 Could not find FAT16/FAT32 partition. Make sure you've formatted the card
So what am I missing? It's worth pointing out that none of the other sample sketches work. It immediately fails with the SD.begin() line. Whether it's set to the hardware SS (pin 10) and I connect the card's CS pin to that, or whether I set it to pin 4. It never seems to get past that line.