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STM32MP157F-DK2

Board Identification

Identifier: STM32MP157F-DK2

Yocto MACHINE: stm32mp15-disco-welma

Documentation:

Features:

  • MPU: STM32MP157f dual ARM Cortex‑A7 32-bit + ARM Cortex‑M4 32-bit
  • GPU
  • RAM: 512 MB DDR3L
  • Storage: microSD
  • RJ45 Ethernet
  • Wi‑Fi
  • Bluetooth
  • 4 USB Host Type-A
  • USB Type-C
  • Video & sound:
    • MIPI DSI
    • HDMI
    • Stereo headset jack including analog microphone input
    • 4" TFT 480×800 pixels with LED backlight, capacitive touch panel
  • 4 user LEDs, 2 user and reset push-buttons, 1 wake-up button

Boot Sequence

The boot sequence is from a SD card, as follows:

  • The ROM Code (BL1) loads TF-A (BL2, FSBL) from the first GPT partition (raw) into SRAM (System RAM inside MPU), and starts it.

  • TF-A:

    • Initializes DRAM (used in the following steps)
    • Loads the FIP container (SSBL) from the partition named "fip"
    • Launches OP-TEE (BL32)

  • OP-TEE launches U-Boot (BL33) (in DRAM)

  • U-Boot starts the kernel
  • The kernel mounts the initial ram file system (initramfs) and starts Init

Reference: https://trustedfirmware-a.readthedocs.io/en/latest/design/firmware-design.html

Glossary:

  • FSBL: First Stage Boot Loader
  • SSBL: Second Stage Boot Loader
  • DRAM: Dynamic RAM, external to the MPU
  • TF-A: Trusted Firmware-A

Notes

  • The ROM code supports loading TF-A from the first or the second GPT partition. But by default on Welma, only the first partition contains TF-A.

  • TF-A Firmware update is not supported in Welma.

First Installation

There are two options for installing software on the board:

  • Flashing the SD card on a PC, as explained in the quick start.
  • Using DFU mode and TFTP, as explained in this section.

First Step: Get U-Boot running in RAM

  • Switch the boot mode pins, to make the ROM Code start in mode DFU over USB:

    • BOOT0 OFF
    • BOOT2 OFF

  • Connect your cables between the board and the PC:

    • Serial port ST-LINK (not actually needed in this step, but gives useful information)
    • USB OTG

  • Power on the board

  • Have the board load and execute TF-A / OP-TEE / U-Boot in RAM: 

    dfu-util --alt 1 --download tmp/deploy/images/stm32mp15-disco-welma/arm-trusted-firmware/tf-a-stm32mp157f-dk2-usb.stm32
dfu-util --alt 3 --download tmp/deploy/images/stm32mp15-disco-welma/fip/fip-stm32mp157f-dk2-optee.bin 
dfu-util --alt 0 --detach

Second Step: Install Welma on the SD Card

This step can be executed after the first step or when booting a previously installed SD card.

  • Connect your cables between the board and the PC:

    • Serial port ST-LINK
    • Ethernet
    • You no longer need USB OTG

  • Insert a SD card to be programmed into the microSD slot of the board

  • Take control of U-Boot, download the SD card image via TFTP and write is to its destination: 

    STM32MP> setenv ipaddr 169.254.142.1; setenv serverip 169.254.142.224;
STM32MP> tftp welma/welma-image-minimal-stm32mp15-disco-welma.wic.gz
STM32MP> gzwrite mmc 0 $loadaddr $filesize

  • Power down the board

Regular Boot

The regular boot is done from SD card, as follows:

  • Switch the boot mode pins, to make the ROM Code start on the SD card:

    • BOOT0 ON
    • BOOT2 ON

  • Power on the board

Appendix

Connecting the board

STM32MP157C-DK2.png

To connect to the console, connect your PC to the ST-LINK/V2-1 (micro-USB, /dev/ttyACM0, 115200 baud).

Boot mode switches

Two switches at the back of the board enable chosing the boot mode.

  • Boot in DFU (Device Firmware Update) mode:

    • BOOT0 OFF
    • BOOT2 OFF

  • Boot from the SD card:

    • BOOT0 ON
    • BOOT2 ON

Hardware Watchdog

The board has 1 hardware watchdog inside the MPU.

/sys/class/watchdog/watchdog0 -> ../../devices/platform/soc/5a002000.watchdog/watchdog/watchdog0
  • Started by U-Boot (timeout 32 s)
  • Serviced by the Linux kernel (as long as no userspace process opens /dev/watchdog0 and takes over)
  • Then serviced by systemd