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TMDSSK3358: Custom boot sequence on TMDSSK3358

Part Number: TMDSSK3358
Other Parts Discussed in Thread: AMIC110

In our project we consider SDIO WiFi adapter + host processor AM3358.
For that reason we are considering TMDSSK3358 - AM335x Starter Kit for evaluation.
According to AM335x specification SDIO interface can be connected via MMC0, MMC1, MMC2.
According to TMDSSK3358 User Guide the MMC0 is defined for SD card (slot on the board) and MMC1 - for WiFi/ BT module (soldered on board), the boot sequence is MMC0, SPI0, UART0, USB0.
In our scenario we could use MMC0 for SDIO WiFi adapter and boot linux OS from USB0? according to defined boot sequence.
Unfortunatelly, we could not find clear information on how to change boot sequence on TMDSSK3358.
Please advise the steps/way to set a boot sequence on TMDSSK3358.

  • Hi,
    I'll look into your inquiry, and get back to early you next week.

  • Hello,
    From the AM335x SK HW user guide (
    3.6.1 Boot Configuration
    The default settings for the TMDSSK3358 is 01_00XX_XXXX_XX11_0111b. This corresponds to a boot sequence of:
    • MMC0
    • SPI0
    • UART0
    • USB0

    For more details, see the TMDSSK3358 schematic. For the definitions of each of the sysboot signals, see
    the AM335x SitaraTm Processors Data Sheet and the AM335x and AMIC110 SitaraTm Processors Technical Reference Manual

    It looks like you would need to change some resistors for sysboot pins in order to change the boot order from the default one.


  • Hi, Hong.
    Thank you for your feedback.

    I see the boot configuration on the shematic you refered me. However, it looks like fo me there is no simple way to change the boot order on the TMDSSK3358. I could not find related jumpers or headers on it.
    Currently, I'm not sure about success on our boot scenario if we connect SDIO wifi adapter to MMC0 and bootable USB drive to USB0. Do you have any experiance on similar case?

  • Hi,
    For changing the boot order from the default one on SDK board, you'd need to install/un-install some resistors for SYSBOOT.
    Regarding SDIO WIFI adapter, we have an early e2e post, and I recite here for your reference:
    1. WLAN module (i.e. WL18xx) is not active during u-boot booting phase, that is why mmc3 node in u-boot device tree needs to be disabled as in my previous post. Note that there's no WL18xx driver in u-boot.
    2. In Linux kernel boot up, kernel device tree would setup mmc3 node for SDIO I/F accordingly, along with WL1800 kernel driver/module installation.

  • Hi, Hong
    Thanks for your reply!

    I still do not understand which resistors need to be installed and which ones to uninstall to change the configuration load.
    Could you explain this moment in more detail?

    We are looking forward to hearing from you.

  • Hi,
    1. Please note from AM335x data sheet:
    (5) LCD_DATA[15:0] terminals are respectively SYSBOOT[15:0] inputs, latched on the rising edge of PWRONRSTn.

    2. From SK schematic (, SYSBOOT pins are in page #6.
    - R171 is installed, and R32 un-installed, SYSBOOT[0] = "1"
    - R171 is un-installed, and R32 installed, SYSBOOT[0] = "0"

    3. You may also refer to AM335x EVM schematic (,
    where DIP switch SW3 and SW4 on page #6 are used to setup SYSBOOT[15:0] as needed

    Hope these info help.