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AM335x will not boot from SD card

Kyle von Schmacht
Prodigy 120 points

Other Parts Discussed in Thread: AM3358, AM3352

We're trying to bring up a custom board based on the BagleBone Black, swapping the AM3358 for the AM3352.

We're using the "default" boot sequence MMC1[NAND] -> MMC0[uSD card]->usb and uart.

The processor has gotten to the point where it prints out "C" to UART0.  The NAND is blank, and so gets skipped, leaving the SD card as the only boot source left.  

When we took a look at the CMD lines for MMC0 we see that it seems to be issuing the correct initialization sequence of commands (CMD0, CMD8, CMD55).  but never receives a response from the SD card.

The same SD cards when placed in a BBB with the NAND blanked boot immediately.  however we saw an entirely different sequence of commands on the CMD line.

Does anyone have any insight into what is going on?

Why are the command sequences so radically different?

As the AM3352 is still operating in TI ROM code at this point is there anything we can do to diagnose or fix the problem?

Thanks for your time,

Kyle von Schmacht

Hardware/Software Engineer 

  • 0
    TI__Guru**** 393215 points
    There are no differences regarding booting between AM3352 and AM3358. You should check that your SYSBOOT values are really what is expected. Are you using the same pins on MMC0 as the BBB?
  • 0 in reply to Biser Gatchev-XID
    Prodigy 60 points
    I have the same problem with a new designed board when I use the same pins as the BBB. I see that the clock is <200kHz, there are some signals on the mmc0_CMD and some signals on the mmc0_Dat0. No signals on the the other DAT-pins (they are high). Do I have a problem with the clock frequency if it is <400kHz? All boot-configurations are the same as with the BBB. Who can help?