MicroSD Card On Carrier Card, No CD (carrier detect) signal


I am designing a carrier card with a MicroSD card, not an SD card. The MicroSD cards do not have the CD (carrier detect signal).

What should I do with the SDCARD_CD# signal? Leave it floating? Connect it to the DAT3 pin that is labeled DATA3_CD? Will the MicroSD card even operate without the SDCARD_CD# pin connected.

I read in another thread that the SDCARD_CD# only turns on the SDCARD_PWR_EN, so I just need to be sure to always keep the 3V3 on for the SDCard.

Thanks for the help.

Hi johnq,

Please try with removing “cd-gpios” from device tree. According to the source code (kernel/drivers/mmc/host/sdhci-tegra.c), it should be working.

Hi John
The card detect is low active I think you should pull it to low.

Hi Shane,

So you are indicating that I should always just keep the SDCARD_CD# pulled low on my carrier card since the MicroSD slot does not have a SDCARD_CD# signal? Rather than floating it or tieing it to CD_DAT3 on MicroSD card?


Not sure why you saied that there is no SDCARD_CD#on your carrier. Actually, the SDCARD_CD# is typically done by a mechanical switch that is built right into the SD Card socket.
anyway, we suggested you to drive the SDCARD_CD#=Low since the system has to see this pin to know the SD CARD is present.
otherwise, the SD card will be unable to work.
BTW, you might get a hot-plug issue if you force the SDCARD_CD# = LOW.