- Ensure that the SD card being used is functional and not corrupted.
- Additionally, reflashing the SD card or testing with a different SD card to rule out card-related issues.
- Probe the given test points and observe that the SD_PWR and SD_PWR ENABLE signals are high and functioning properly. However, the SD_CARD DETECT signal is low, no transitions observed.
- Try performing the SD card boot test to escalate the issue, refer Software User Guide for performing the test.
- Please check the voltage at SDIO_A_IOPWR, refer Hardware User Guide.
- Check the voltage in eMMC boot mode—once in U-Boot and again in the kernel. In both cases, the MicroSD card should be mounted.
- SD_PWR_ENABLE measures 1.8 V in U-Boot and remains 1.8 V after the kernel is loaded.
- SDIO_A_IOPWR measures 1.8V or 3.3V (based on the Micro SD used) in U-Boot but rises to 1.8V or 3.3V after the kernel is loaded. Check Hardware User Guide for pin details and test points.
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Please find the detailed G55M product information in the below link,