Update faq.adoc with memory.x definition helping hand

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@ -208,3 +208,24 @@ Tools like `cargo size` and `cargo nm` can tell you the size of any globals or o
=== For Max Stack Usage
Check out link:https://github.com/Dirbaio/cargo-call-stack/[`cargo-call-stack`] for statically calculating worst-case stack usage. There are some caveats and inaccuracies possible with this, but this is a good way to get the general idea. See link:https://github.com/dirbaio/cargo-call-stack#known-limitations[the README] for more details.
== The memory definition for my STM chip seems wrong, how do I define a `memory.x` file?
It could happen that your project compiles, flashes but fails to run. The following situation can be true for your setup:
The `memory.x` is generated automatically when enabling the `memory-x` feature on the `embassy-stm32` crate in the `Cargo.toml` file.
This, in turn, uses `stm32-metapac` to generate the `memory.x` file for you. Unfortunately, more often than not this memory definition is not correct.
You can override this by adding your own `memory.x` file. Such a file could look like this:
```
MEMORY
{
FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 1024K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 320K
}
_stack_start = ORIGIN(RAM) + LENGTH(RAM);
```
Please refer to the STM32 documentation for the specific values suitable for your board and setup. The STM32 Cube examples often contain a linker script `.ld` file.
Look for the `MEMORY` section and try to determine the FLASH and RAM sizes and section start.