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BEAGL-BONE-BLACK: Flashing over serial wire via external MCU

Ezra Wolf
Prodigy 10 points
Part Number: BEAGL-BONE-BLACK
Other Parts Discussed in Thread: AM3358

Tool/software:

Hello,

We have bought a few BeagleBone Black's (BBBs) for R&D since we will be using the AM3358 in a custom board.

As part of our requirements we need to be able to program the AM3358 via a secure MCU with WiFi capabilities to perform secured OTA updates.

Are there any guides online that demonstrate how to flash the eMMC for the AM3358 or BeagleBone Black via SPI, I2C, etc. instead of USB or SD card?

Thanks.

  • 0
    TI__Guru**** 156341 points

    Hi Ezra,

    Please review the AM335x TRM Initialization chapter, the AM335x ROM does support boot from SPI or I2C. but it is from memory on SPI0 or I2C0, such as EEPROM. I am not sure it is what you can use for OTA update.

  • 0 in reply to Bin Liu
    Prodigy 10 points

    Hi Bin Liu, thank you for letting me know! As long as the AM335x's can be flashed somehow via SPI or I2C, any MCU that can send and receive those signals is a starting point. I believe OTA would simply receive the data and pass it along minus some nuances with security, processing serial / web commands, etc.

    You are saying that the EEPROM inside or outside of the AM335x will need to be flashed? Then the AM335x will boot from that EEPROM?

  • 0 in reply to Ezra Wolf
    TI__Guru**** 156341 points

    Hi Ezra,

    Since none of the AM335x EVMs has such capability, I don't think these SPI and I2C boot features have been validated with the Processor SDK, but based on the information in the TRM, I believe it is that the external EEPROM on the board already has the boot image, once AM335x is powered on, its ROM downloads the boot image from the EEPROM via SPI or I2C and boots from there.

  • 0 in reply to Bin Liu
    Prodigy 10 points

    I see. So the device would need to be plugged in or continue using an SD Card to be programmed correct? Unless the external MCU has USB capabilities and could program it through that?

  • 0 in reply to Ezra Wolf
    TI__Guru**** 156341 points

    Yes, AM335x can be booted and programmed using a SD card, or through CPSW Ethernet or USB Ethernet.

    UART0 can be used for flashing too, but it would be slow if the firmware is big in size,

  • 0 in reply to Bin Liu
    Prodigy 10 points

    Spending some time to read through the Technical Reference Manual, in section 26.1 (Initialization -> Functional Description) it states that UART, USB, Ethernet, all are ways to boot via a peripheral. In the figures 26-2 and 26-3 it explains the process of how booting works.

    I am under two impressions with my limited knowledge

    1. If there is a memory device such as eMMC, SPI flash, or SD card, it will attempt to boot from that first even if there is a valid peripheral device to boot from. Would this be correct?

    2. To boot from a peripheral device, the program memory that is then loaded into the AM335x is only help temporarily inside of RAM, meaning if the peripheral was removed and the device was reset, it would have nothing to boot to. Would this also be correct?

    Given this, is it possible to use a peripheral device using UART0 to interface with the AM335x to flash either the public or secure ROM sectors on an eMMC, SD card, etc., so that program memory is stored in its designated memory sector, and can then boot like normal from a memory device as shown in figures 26-2 and 26-3?

    Again, thank you so much for your help and patience with me.

  • 0 in reply to Ezra Wolf
    TI__Guru**** 156341 points

    Hi Ezra,

    Ezra Wolf said:
    1. If there is a memory device such as eMMC, SPI flash, or SD card, it will attempt to boot from that first even if there is a valid peripheral device to boot from. Would this be correct?

    Not really. When multiple memory and peripheral devices are available, the boot order is determined by the SYSBOOT pin settings. Please see the TRM section 26.1.6 "Booting" for details.

    Ezra Wolf said:
    2. To boot from a peripheral device, the program memory that is then loaded into the AM335x is only help temporarily inside of RAM, meaning if the peripheral was removed and the device was reset, it would have nothing to boot to. Would this also be correct?

    Correct. peripheral boot downloads the bootable firmware to DDR then executes it. However, after AM335x is booted from the peripheral device, the peripheral can continue be used to download and program the memory device (eMMC, NAND flash, etc) for future boot.

    Ezra Wolf said:
    Given this, is it possible to use a peripheral device using UART0 to interface with the AM335x to flash either the public or secure ROM sectors on an eMMC, SD card, etc., so that program memory is stored in its designated memory sector, and can then boot like normal from a memory device as shown in figures 26-2 and 26-3?

    Basically correct, except that the program to be flashed to eMMC, SD card, etc is not the ROM sectors, rather the secondary boot loader and application or Linux. The ROM sectors are already in the AM335x device and runs every time AM335x is powered on or reset.

    By the way, UART would be slow (only at 115200bps baud rate) for flashing if the to-be-flashed program is big in size. Ethernet or USB-Ethernet boot/flashing would be a better choice in such use cases.