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Update embedded-workshop-book/src/uarte-implementation.md

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Co-authored-by: Jonathan Pallant <jonathan.pallant@ferrous-systems.com>
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Tanks Transfeld 2023-03-20 14:37:28 +01:00 committed by Mirabellensaft
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embedded-workshop-book/src/uarte-implementation.md
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@ -124,7 +124,11 @@ pub fn init() -> Result<Board, ()> {
### Step 6: Implementing the `fmt::Write` trait
We can't just write to the `Uarte` instance. A simple write would write from flash memory. This does not work because of EasyDMA. We have to write a function that implements the `fmt::Write` trait. This trait guarantees that the buffer is fully and successfully written on a stack allocated buffer, before it returns.
We want to implement the `fmt::Write` trait so that users can call `write!` on our Uarte object
When implementing this, we can't just write to the `Uarte` instance because a simple write of a string literal would try and read the string literal from flash memory. This does not work because the EasyDMA peripheral in the nRF52 series can only access RAM, not flash.
Instead our implementation must ensure all the strings are copied to a stack allocated buffer and that buffer is passed to the Uarte's `write` method.
✅ Add `use::core::fmt;` to your imports.