Booting from SD Card

NOTE: The AM62x has multiple MMC interfaces. Booting is not supported on MMC2

To boot the Dev Kit from SD card using a CL supplied image, set the boot pins as follows:

B9 B8 B7 B6 B5 B4 B3
Port (1) Reserved (0) Fs/raw (0) 1 0 0 0

The first partition on the SD card is a FAT32 and must contain the following files

  • tiboot3.bin
  • tispl.bin
  • u-boot.img

Hardware design considerations

To support switching to higher bus speeds (UHS SDR12/SDR25/SDR50/DR50/SDR104) on MMC1, the SD card spec requires switching the SD card voltage levels from 3.3V to 1.8V. Pin 176 (VSEL_SD) should be connected to a gpio to allow for the sd card voltage to be switched between 3.3V and 1.8V. The devkit uses pin 174 (GPIO0_31) so it's recommended to also use this gpio if possible to make bring up easier.

Operating in 3.3v mode only (No 1.8V)

It is possible to operate the SD card in 3.3V mode only, however, the device tree will need to be modified to ensure it doesn't attempt to switch modes. In this case, the VSEL_SD pin should be left floating.

 &sdhci1 {
     /* SD/MMC */
     vmmc-supply = <&vdd_mmc1>;
-    vqmmc-supply = <&som_vdd_sd_dv>;
+    vqmmc-supply = <&vdd_mmc1>;
     pinctrl-names = "default";
     pinctrl-0 = <&main_mmc1_pins_default>;
     ti,driver-strength-ohm = <50>;
+    /* Disable 1.8V mode when VSEL_SD is not controllable */
+    no-1-8-v;

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