PAC1934 Energy Metering Using Linux Step 3

Create a directory for the BR2_EXTERNAL outside the main Buildroot directory using the following commands:

/my_external_tree/
|  +-- board/
|    +-- my_company/
|      +-- my_board/
|
|  +-- configs/
|  +-- package/
|  +-- patches/
|
|  +-- Config.in
|  +--external.mk
|  +-- external.desc

Change directory to my_external_tree

Create the necessary files for the BR2_EXTERNAL using the following command:

Create the other subfolders within my_external_tree using the following command:

Add a basic description of the project within external.desc using your preferred text editor. For this tutorial, we will use nano as shown:

The external.desc contents should contain the following information:

name: <external_tree_name>
desc: <Your project description>

Make sure my_external_tree is the current working directory

Run menuconfig using the following command:

The main menu screen of menuconfig should appear.

We will configure our project from scratch (without using any defconfigs). This will allow us to create a project without any unnecessary packages installed.

Enter the Target options menu and configure the following options:

• Target Architecture: ARM (little endian)
• Target Binary Format: ELF
• Target Architecture Variant: cortex-A5
• Enable NEON SIMD extension support
• Enable VFP extension support
• ARM instruction set: ARM

Your screen should now look like the accompanying screenshot shown:

Save the configuration by selecting Save from the bottom screen options and pressing Enter. Do not change the default options, then press Enter again.

Enter the Build options menu and configure the following option:

• Location to save buildroot config:

Your screen should now look like:

​

Save the configuration and navigate back to the main menu screen.

Enter the Toolchain menu and configure the following options:

• Enable WCHAR Support
• Enable toolchain locale/i18n support:
• Enable C++ support

Your screen should look like this screenshot:

Save the configuration and navigate back to the main menu screen.

Enter the System configuration menu and configure the option as shown:

• Root password:
  • root

• Network interface to configure through DHCP:
  • eth0

• Custom scripts to run after creating filesystem images:
  • support/scripts/genimage.sh

• Extra arguments passed to custom scripts

Your screen should look like:

​

Save the configuration and navigate back to the main menu screen.

Enter the kernel menu and configure the Linux kernel options:

• Linux Kernel

Additional options will appear after selecting Linux kernel. Configure the following options:

• Kernel version: Custom Git repository
• URL of custom repository: https://github.com/linux4sam/linux-at91.git
• Custom repository version: linux4sam-2021.04
• Deconfig name: sama5
• Build a Device Tree Blob (DTB):
• In-tree device tree source file names: at91-sama5d27_som1_ek
• Needs host OpenSSL

Your screen should look like:

Save the configuration and navigate back to the main menu screen.

Enter the Filesystem images menu and configure the options:

• ext2/3/4 root filesystem
• ext2/3/4 variant: ext4

Your screen should look like:

Save the configuration and navigate back to the main menu screen.

Enter the Bootloaders menu and configure the options:

• T91 Bootstrap 3+
• AT91 Bootstrap 3+ version: Custom Git repository
• URL of custom repository: https://github.com/linux4sam/at91bootstrap.git
• Custom repository version: v4.0.0
• Deconfig name: sama5d27_som1_eksd_uboot

• U-Boot
  • Build system: Kconfig
  • U-Boot Version: Custom Git repository
  • URL of custom repository: https://github.com/linux4sam/u-boot-at91.git
  • Custom repository version: linux4sam-2021.04
  • Board deconfig: sama5d27_som1_ek_mmc
  • U-Boot needs dtc

Your screen should look like this screenshot:

Save the configuration and navigate back to the main menu screen.

Enter the host utilities menu and configure the options:

• host genimage
• host u-boot-tools
• Flattened Image Tree (FIT) support
• Environment image
• Source files for environment: $(BR2_EXTERNAL_MCHP_PATH)/board/microchip/sama5d27_som1_ek/uboot-env.txt
• Size of environment: 0x4000

Your screen should look like the accompanying screenshot:

Save the configuration and navigate back to the main menu screen.

Enter the external options menu and then the MCHP menu and configure the options:

• dt-overlay-at91
• platform name: sama5d27_som1_ek
• output: FIT image

Your screen should look like:

Recommended Target Packages

Enter the Target packages menu from the main menu screen. Install the following packages by navigating to the specified submenus.

1. i2c-tools – for checking devices in I2C bus
2. spi-tools – includes “spi-config” and “spi-pipe” for configuring and testing Serial Peripheral Interface (SPI).
3. lshw – for checking drivers loaded to a specific device.
4. evtest – for testing General Purpose Input/Output (GPIO) events on the SOM1-EK.

Target packages

• [*] Show packages that are also provided by busybox

Target packages —-> Hardware handling

• <*> evtest
• <*> i2c-tools
• <*> lshw
• <*> spi-tools

Your screen should look like this screenshots:

nano – for editing files within the target device.

Target packages —-> Text editors and viewers

• [*] nano
• [*] optimize for size

libgpiod – includes tools like gpiodetect, gpioinfo etc. which can be helpful in checking GPIO.

Target packages —> Libraries —> Hardware handling

• [*] libgpiod
• [*] install tools

openssh – for connecting to the target device via ssh and transferring files via scp

Target packages —-> Networking applications

• [*] openssh
• [*] client
• [*] server
• [*] key utilities

Install the following packages by navigating to the specified submenus relative to the main menu screen:

• 1. python3
  • Target packages —-> Interpreter languages and scripting
  • [*] python3
  • python3 module format to install (.pyc compiled sources only)

• 2. python-spidev
  • Target packages —> Interpreter languages and scripting —> External python modules
  • [*] python-spidev

• 3. python-mpio
  • External options —-> MCHP
  • [*] python-mpio