Zephyr RTOS

Device Tree

Zephyr Device Tree Mysteries, Solved.
The device tree is parsed at compile time and converted in to C header files

All device tree info is accessible at compile time via the zepher/devicetree api

How zephyr.dts gets converted to devicetree_unfixed.h

Macrobatics is the solution to having quotes in fields

DT_N = devicetree node
Anytime there is a slash, it's replaced with a capital S
DT_N_S_parent_S_child would be /parent/child
so DT_N_S_foo_S_bar would be /foo/bar

These ARE NOT VALUES they are just tokens
But...we can use them to get the value without any over the overhead that we're trying to avoid

Capital P is property, followed by the name of the property, in this case, "size "

This is why we lowercase and underscore

Device Tree Bindings

Device tree bindings are basically schema for nodes and is a description of what the node may contain. Necessary to preform the conversion to C

Important Device Tree Properties

• Compatible: the name of the hardware a node represents, typically vendor, device. Used to find the bindings for a node.
• Label: Name of the device(unique)
• reg Information used to address the device (optional) value meaning depends on the device. In general, a sequence of address-length pairs.
• status: status of the device (ok or disabled)

You can have multiple instances of a device and each can have its own properties