Device tree files
Device tree file types
The device tree is a set of text files in the Linux kernel source tree that describe the hardware of a certain platform. They are located at arch/arm/boot/dts/ and can have two extensions:
- *.dtsi files are device tree source include files. They describe hardware that is common to several platforms which include these files on their *.dts files.
- *.dts files are device tree source files. They describe one specific platform.
ConnectCore 6UL system-on-module
The ConnectCore 6UL is a system-on-module (SOM) solution that integrates:
- NXP i.MX6 UltraLite system-on-chip featuring many interfaces such as UART, CAN, SPI, and I2C
- DDR3 memory
- NAND flash memory
- PMIC chip
- Micro Controller Assist (MCA) chip
-
Optional Wi-Fi + Bluetooth chip
The ConnectCore 6UL system-on-module needs to be soldered to a carrier board. For this reason, there is not a single *.dts file for it. Instead, its hardware features are collected into *.dtsi files that can be included by a final platform *.dts.
Since the ConnectCore 6UL system-on-module is offered in different variants, multiple *.dtsi files have been defined to describe the hardware inside:
| File | Description |
|---|---|
| imx6ul-ccimx6ul.dtsi | Common hardware for ConnectCore 6UL system-on-module (SOM) variants |
| imx6ul-ccimx6ul-wb.dtsi | ConnectCore 6UL system-on-module variant with wireless and Bluetooth |
Depending on your ConnectCore 6UL variant, your final platform *.dts file will need to include one of these files.
ConnectCore 6UL SBC Express and ConnectCore 6UL SBC Pro
The ConnectCore 6UL SBC Express and ConnectCore 6UL SBC Pro are carrier boards assembling the ConnectCore 6UL system-on-module. Both boards assemble additional hardware such as Ethernet PHY, microSD card holder, or user LEDs.
As final platforms, both boards have *.dts files that include one of the ConnectCore 6UL system-on-module *.dtsi files.
Include files
Both the SBC Express and the SBC Pro boards can assemble different variants of the ConnectCore 6UL system-on-module, so the common hardware for the carrier boards is described in a board-specific .dtsi file:
| File | Description |
|---|---|
| imx6ul-ccimx6ulstarter.dtsi | Common hardware for ConnectCore 6UL SBC Express |
| imx6ul-ccimx6ulsbc.dtsi | Common hardware for ConnectCore 6UL SBC Pro |
Final platform files
The final platforms are described in board-specific *.dts files:
| File | Digi product smart part number | Wireless | Bluetooth |
|---|---|---|---|
| imx6ul-ccimx6ulstarter-id129.dts | CC-WMX6UL-START | ✓ | ✓ |
| imx6ul-ccimx6ulsbc-id135.dts | CC-WMX6UL-KIT | ✓ | ✓ |
Note The device tree files without ID number are not linked to any Digi product. They correspond to:
- imx6ul-ccimx6ulsbc-wb.dts: generic device tree file for an SBC Pro with a wireless+Bluetooth SOM
- imx6ul-ccimx6ulsbc.dts: generic device tree file for an SBC Pro with a non-wireless SOM
- imx6ul-ccimx6ulstarter-wb.dts: generic device tree file for an SBC Express with a wireless+Bluetooth SOM
- imx6ul-ccimx6ulstarter.dts: generic device tree file for an SBC Express with a non-wireless SOM
Graphical representation
The following graphic illustrates the composition of a .dts file.
Device tree selection during boot process
Digi Embedded Yocto builds the different device tree files (*.dts) for different boards and SOM variants into binary device tree blobs (*.dtb). The device tree blobs are placed inside the linux partition along with the kernel binary.
The bootloader uses the BOARD_ID variable to determine which device tree blob to use when booting the system. See Carrier board version and ID.
Note To learn how to create a device tree for your custom carrier board and using a custom board ID, see Customize Digi Embedded Yocto for your carrier board.
