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doc: tracing: add ram backend

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This add documentation on how to use the tracing ram backend.

Signed-off-by: Julien Massot <julien.massot@iot.bzh>
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Julien Massot 2021-03-04 14:57:05 +01:00 • committed by Anas Nashif
commit 3be1c120ad
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doc/guides/tracing/index.rst
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@ -155,6 +155,7 @@ The following backends are currently supported:
* USB
* File (Using native posix port)
* RTT (With SystemView)
* RAM (buffer to be retrieved by a debugger)
Using Tracing
*************
@ -182,6 +183,20 @@ the tracing data::
The resulting CTF output can be visualized using babeltrace or TraceCompass
by pointing the tool to the ``data`` directory with the metadata and trace files.
Using RAM backend
=================
For devices that do not have available I/O for tracing such as USB or UART but have
enough RAM to collect trace datas, the ram backend can be enabled with configuration
`CONFIG_TRACING_BACKEND_RAM`.
Adjust `CONFIG_RAM_TRACING_BUFFER_SIZE` to be able to record enough traces for your needs.
Then thanks to a runtime debugger such as gdb this buffer can be fetched from the target
to an host computer::
(gdb) dump binary memory data/channel0_0 <ram_tracing_start> <ram_tracing_end>
The resulting channel0_0 file have to be placed in a directory with the ``metadata``
file like the other backend.
Visualisation Tools
*******************