To identify which capes are plugged in, all you have to do is read the connected EEPROMs. BeagleBone Black with multiple capes – We want to detect them automatically! Accessing cape informationĮach cape has to contain an I2C EEPROM describing itself, according to the Cape EEPROM Contents specification. This would be great if each cape could be detected automatically and so could be the corresponding overlays.Īctually, all this is possible and already supported in mainline U-Boot starting from version 2021.07. This mechanism works fine, but every time you plug in a different cape, you have to tweak this sequence of commands to load the right overlay (the. Once you know which capes are plugged in, you can load them in U-Boot and boot Linux as in the following example: load mmc 0:1 0x81000000 zImage As the available hardware is described by a Device Tree, the added devices on the cape should be described using a Device Tree Overlay, as described in the first blog post.Īs explained in this post too, the bootloader is today’s standard place for loading Device Tree Overlays on top of the board’s Device Tree. When such a cape is plugged in, the description of the devices connected to the board should be updated accordingly. Device Tree: Supporting Similar Boards – The BeagleBone ExampleĪs explained in the first two blog posts, the BeagleBone boards are supported by a wide number of extension boards, called capes.
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Using Device Tree Overlays, example on BeagleBone boards.This article follows two earlier blog posts about Device Tree overlays: