Using DAT3/CD as card detect pin on microsd-cards

Technical Support
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1

Hi, we are using Verdin-IMX8MM on a custom carrier board together with Toradex Yocto BSP 5.2.

The micro-SDCard socket on our carrier board has no dedicated card detect pin. We want to use DAT3/CD pin instead, according this application note: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjMs4mG2MvyAhVJKBoKHYKBBssQFnoECAUQAQ&url=https%3A%2F%2Fwww.mouser.com%2Fdatasheet%2F2%2F302%2FAN10911-112956.pdf&usg=AOvVaw3tVSahuJP-OGo3layczDAA

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Question: Does the SDCard driver sdhci-esdhc-imx support this card detection method? If yes, how to activate it?

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Hi @klausci

According to the Datasheet you shared the CardDetect has to be realized on Hardware. We recommend you to use a separate GPIO for CardDetect. We never tested this multiplexed version of DAT3/CD on our carrier boards but you can test this on the Toradex Verdin Evaluation Board.

I also found this NXP Thread, where a solution was discussed for iMX6.

Best regards,
Jaski

3

Hi @jaski.tx ,
Thanks for your reply. I know that the recommended implementation of CardDetect is via a mechanical switch, but our cardholder doesn’t provide one, due to mechanical constraints.

I was already aware of the s NXP Thread, however, it’s from 2013 and I was hoping that the driver is now capable of handling the DAT3/CD mechanism. Anyway I will dig deeper and post my results here.
Best Regards, Klaus

4

Perfect. Let us know your results.

Best regards,
Jaski

5

We gave up this approach. The DAT3/CD pin can be used only in 1-pin SDCard mode and this is not what we want.

6

Ok, so you go for a proper hardware solution?

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Yes, either by using a SDCard Holder with mechanical CD pin, or by using some solution that detects the opening of our flap in front of our SDCard

8

Perfect. Thanks for the feedback.