A simple bootloader

Purpose

  • Understand the memory map of ARC boards
  • Understand the principles of bootloader and self-booting
  • Understand the usage of shell commands in cmd
  • Create a self-booting application

Requirements

The following hardware and tools are required:

  • PC host
  • GNU Toolchain for ARC Processors / MetaWare Development Toolkit
  • ARC board (EM Starter Kit / IoT Development Kit)
  • SD card
  • example/baremetal/bootloader

Simple Bootloader

This simple bootloader is designed to work as a secondary/simple bootloader for embARC OSP, it loads boot.hex or boot.bin on SD Card and run that program. The example can be used as ntshell application.

The following features are provided in this simple bootloader:

  • Boot application from SD card
  • File operations on SD card
  • UART Y-modem protocol to update application
  • Operations on ARC processors

Content

  1. Build and run the example/baremetal/bootloader
  2. Download the generated bootloader.bin into flash
  3. Build a self-boot application and boot it from SD card
  4. Use the ntshell commands

Principles

Memory Map of ARC board

EM Starter Kit

The available memory regions of EM Starter Kit are shown below:

Memory Map of EM Starter Kit
Name Start address Size
on-chip ICCM 0x00000000 256/128 KB
on-chip DCCM 0x80000000 128 KB
on-board DDR RAM 0x10000000 128 MB

In this lab, the last 1 MB of DDR (starting from 0x17f00000) is reserved for the simple bootloader, other memory regions are available for application.

IoT Development Kit

The available memory regions of IoT Development Kit are shown in the following table:

Memory Map of IoT Development Kit
Name Start address Size
on-chip eflash 0x00000000 256 KB
external boot SPI flash 0x10000000 2 MB
on-chip ICCM 0x20000000 256 KB
on-chip SRAM 0x30000000 128 KB
on-chip DCCM 0x80000000 128 KB
on-chip XCCM 0xC0000000 32 KB
on-chip YCCM 0xE0000000 32 KB

In this lab, on-chip eflash and on-chip SRAM are reserved for the simple bootloader, CCMs are reserved for application.

Boot of ARC board

EM Starter Kit

The EM Starter Kit uses a Xilinx SPARTAN-6 FPGA part which can be configured to run different members of the ARCv2 EM Processor family. The EMSK includes a SPI flash pre-programmed with four FPGA configurations of ARC EM cores.

When a “power on” or reset/configure is issued, the FPGA auto-loads one of the pre-installed FPGA configurations from SPI flash. After the FPGA configuration is loaded from the SPI flash, a simple primary bootloader is loaded in ICCM. Through the primary bootloader, an application can be loaded from SPI Flash into ICCM or external DDR memory.

Considering that the SPI Flash is used to store FPGA images, the secondary bootloader is designed based on the primary bootloader to load an application from an SD card since it can be read and written easily. The startup sequence is listed below:

  1. Power on or reset event.
  2. Load FPGA configuration from the SPI flash.
  3. Run primary bootloader, which loads the secondary bootloader from the SPI Flash into main memory (DDR).
  4. Run secondary bootloader from main memory to load application from the SD card into ICCM/DDR memory.
  5. Run the application from ICCM/DDR memory.
Boot sequence of EMSK

IoT Development Kit

IoT Development Kit can boot from on-chip eflash and extern boot SPI flash, which is decided by the FWU switch of IOTDK. When this switch is set to “off”, the processor starts executing the program stored in on-chip eflash; When this switch is set to “on”, the processor starts executing the program stored in external boot SPI eflash. The simple bootloader can be written to both flash to load an application from the TF card. The startup sequence for IoT Development Kit is listed below:

  1. Power on or reset event
  2. Boot from on-chip eflash or extern boot SPI flash decided by the FWU switch
  3. Run simple bootloader to load application from the TF card into ICCM
  4. Run the application from ICCM memory

How to flash the ARC board

EM Starter Kit

  • Generate a secondary bootloader binary file
$ cd <embarc_root>/example/baremetal/bootloader
$ make BOARD=emsk BD_VER=22 CUR_CORE=arcem7d TOOLCHAIN=gnu bin
  • Program the secondary bootloader binary file into SPI Flash

    • Insert SD card to your PC, and copy the binary file obj_emsk_22/gnu_arcem7d/emsk_bootloader_gnu_arcem7d.bin to SD card root folder, and rename it to em7d_2bt.bin

    • Insert the SD card to EMSK Board, choose the right core configuration, build and run the <embARC>/example/baremetal/bootloader example, then press any button to stop auto boot process, and enter to ntshell command mode

    • Use ntshell command spirw to program the em7d_2bt.bin into spiflash
      • Run spirw to show help
      • Run spirw -i to check SPI Flash ID, it should be Device ID = ef4018
      • Run spirw -w em7d_2bt.bin 0x17f00000 0x17f00004 to program spiflash
      • Check the output message to see if it has been programmed successfully
      ../../_images/lab6_emsk_bootloader_program2spiflash.jpg

    • If programmed successfully, when the board is reset, make sure Bit 4 of the on-board DIP switch is ON to enable secondary bootloader run

    • If the SD card already contains the boot.bin in it, the bootloader automatically loads it from SD card. If not, it enters to ntshell mode

    • You can goto the next step to generate the boot.bin for proper application you want to be auto-loaded in SD card

    ../../_images/lab6_emsk_bootloader_onspiflash.jpg

  • Generate boot.bin using any embARC example, it’s RAM start address should be 0x10000000. Use bootloader to run it

  • Known Issues
    • Boot rom of EMSK1.x is not able to load secondary bootloader on SPI Flash, you need a modified EMSK1.x mcs file to enable this function, send request in forum about this mcs file.

IoT Development Kit

  • Generate a secondary bootloader binary file
$ cd <embarc_root>/example/baremetal/bootloader
$ gmake BOARD=iotdk BD_VER=10 CUR_CORE=arcem9d TOOLCHAIN=mw LOCATION=eflash bin
  • Program the secondary bootloader binary file into SPI Flash
    • Insert SD card to your PC, and copy the binary file obj_iotdk_10/mw_arcem9d/simple_bootloader_mw_arcem9d.bin to SD card Root, and rename it to simple_bootloader.bin
    • copy the file example/bootloader/boot.json to SD card root, and change the boot_file value to boot.bin, and change the ram_startaddress to 536870912(0x20000000)
    ../../_images/lab6_iotdk_bootloader_bootjson.jpg
    • Insert the SD card to iotdk Board, build and run the <embARC>/example/baremetal/bootloader example, and enter to ntshell command mode
    $ cd <embarc_root>/example/baremetal/bootloader
$ gmake distclean
$ gmake BOARD=iotdk BD_VER=10 CUR_CORE=arcem9d TOOLCHAIN=mw run
    • Use ntshell command flash to program the simple_bootloader.bin into both flash
      • Run flash -h to show help
      • Run flash -eflsh simple_bootloader.bin to program eflash
      • Run flash -bootspi simple_bootloader.bin to program bootspi flash
      • Check the output message to see if it was programmed successfully
      ../../_images/lab6_iotdk_bootloader_program2spiflash.jpg

    • If the SD card already contains the boot.bin and boot.json in it, the bootloader automatically loads it from SD card, if not, it enters to ntshell mode

    • You can goto the next step to generate the boot.bin for proper application you want to be auto-loaded in SD card

    ../../_images/lab6_iotdk_bootloader_onspiflash.jpg

  • Generate boot.bin using any embARC example, its RAM start address should be 0x20000000. Use bootloader to run it

Exercises

  1. Create and build a different self-boot embARC application
  2. Use the ntshell commands
  3. Use the UART-ymodem to load your application