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:
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.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.
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.dts files are device tree source files. They describe one specific platform.
ConnectCore 6 system-on-module
The ConnectCore 6 is a system-on-module (SOM) solution that integrates:
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NXP i.MX6 system-on-chip featuring many interfaces such as UART, CAN, SPI, and I2C
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DDR3 memory
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eMMC memory
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PMIC chip
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Optional Wi-Fi chip
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Optional Bluetooth chip
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Optional Kinetis chip
The ConnectCore 6 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 6 system-on-module is offered in different variants, multiple .dtsi files have been defined to describe the hardware inside:
| File | Description |
|---|---|
Common hardware for ConnectCore 6 system-on-chip (SOC) variants with either Quad/Dual CPU or Solo/DualLite CPU |
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ConnectCore 6 system-on-module variant with Quad/Dual CPU and wireless (no Bluetooth) |
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ConnectCore 6 system-on-module variant with Quad/Dual CPU, wireless, and Bluetooth |
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ConnectCore 6 system-on-module variant with Solo/DualLite CPU and wireless (no Bluetooth) |
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ConnectCore 6 system-on-module variant with Solo/DualLite CPU, wireless, and Bluetooth |
Depending on your ConnectCore 6 variant, your final platform .dts file will need to include one of these files.
ConnectCore 6 SBC
The ConnectCore 6 SBC is a carrier board assembling the ConnectCore 6 system-on-module. The SBC assembles additional hardware like HDMI, Ethernet PHY, audio chip, PCIe minicard, microSD card holder, user LEDs, and so on.
As a final platform, the SBC has a .dts file that includes one of the ConnectCore 6 system-on-module .dtsi files.
Include files
The SBC can assemble different variants of the ConnectCore 6 system-on-module, so the common hardware of the SBC is also described in several .dtsi files:
| File | Description |
|---|---|
Common hardware for ConnectCore 6 SBC assembling a Quad/Dual or Solo/DualLite ConnectCore 6 system-on-module |
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Common hardware for ConnectCore 6 SBC assembling a Quad/Dual ConnectCore 6 system-on-module |
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Common hardware for ConnectCore 6 SBC assembling a Solo/DualLite ConnectCore 6 system-on-module |
The last two files include the common file imx6qdl-ccimx6sbc.dtsi.
Final platform files
The final platforms are described in board-specific .dts files:
| File | Digi product smart part number | CPU family | Wireless | Bluetooth |
|---|---|---|---|---|
CC-SB-WMX-J97C |
Quad/Dual |
✓ |
✓ |
|
CC-SB-WMX-L87C |
Quad/Dual |
✓ |
✓ |
|
CC-SB-WMX-L76C |
DualLite/Solo |
✓ |
✓ |
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.
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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. To learn how to create a device tree for your custom carrier board and using a custom board ID, see Add a new custom machine. |
