How SD Card pull-up resistores handle in Torizon OS SD-Card Drives?

Technical Support
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Hello All,

We are using Verdin iMX8MP SOM and build our custom reference minimal Torizon OS. I want to check and confirm whether SD card pull-up regsiter properly handled in SD card driver firmware?

Because the below document said when SD card remove the respective pull-up resistors need to be disabled in FW.

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Is this taken care by SD card driver firmware internally, please confirm?

Thanks in advanced..!!

2

Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

SD Card Pull-Up Resistor Configuration on Verdin iMX8M Plus

Hardware Configuration

The Verdin iMX8M Plus includes internal pull-up resistors on the SD card interface (1). According to the datasheet, for the Always Compatible SD Card Interface (USDHC2), the pull-up resistors are enabled on the SoC level for the following signals (1):

  • SD_1_CMD (USDHC2_CMD) - Command line
  • SD_1_D0 through SD_1_D3 (USDHC2_DATA0-3) - Data lines
  • SD_1_CD# (USDHC2_CD_B) - Card Detect

Driver Implementation

The SD/MMC driver automatically handles card insertion and removal (2). When an SD card is inserted, it appears as a /dev/mmcblk<id> block device, and the kernel exports card partitions with appendix p<x> (2).

You can verify proper SD card detection by checking system logs (2):

# dmesg | egrep "(sdhci|mmc)"

(2)

Or check for system interrupts triggered upon SD card insertion (2):

# cat /proc/interrupts | egrep "(mmc|cd)"

(2)

Pull-Up Resistor Management

The documentation states that no external pull-up resistors are required on the carrier board as there are pull-up resistors on the module (1). The SD interface supports both 3.3V and 1.8V IO voltage levels for UHS-I compatibility (1).

Verification Commands

To verify your SD card is properly detected and configured, you can use (2):

# ls -l /dev/verdin-sd*

(2)

This will show the corresponding /dev/mmcblk<id> block device when a card is inserted (2).

Conclusion

Based on the Toradex documentation, the SD card driver firmware does handle pull-up resistor configuration internally. The hardware design includes on-module pull-up resistors, and the driver manages the card detection and interface configuration automatically when cards are inserted or removed.

Best regards, Toradex AI Assistant.

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