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26 lines
1.4 KiB
Markdown
26 lines
1.4 KiB
Markdown
# HAL Layer Readme
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The HAL layer is designed to be used by the drivers. We don't guarantee the stability and back-compatibility among
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versions. The HAL layer may update very frequently with the driver. Please don't use them in the applications or treat
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them as stable APIs.
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The HAL layer consists of two layers: HAL (upper) and Lowlevel(bottom). The HAL layer defines the steps and data
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required by the peripheral. The lowlevel is a translation layer converting general conceptions to register configurations.
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## Lowlevel
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This layer should be all static inline. The first argument of LL functions is usually a pointer to the beginning address
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of the peripheral register. Each chip should have its own LL layer. The functions in this layer should be atomic and
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independent from each other so that the upper layer can change/perform one of the options/operation without touching the
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others.
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## HAL
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This layer should depend on the operating system as little as possible. It's a wrapping of LL functions, so that the upper
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layer can combine basic steps into different working ways (polling, non-polling, interrupt, etc.). Without using
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queues/locks/delay/loop/etc., this layer can be easily port to other os or simulation systems.
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To get better performance and better porting ability, ``context``s are used to hold sustainable data and pass the parameters.
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To develop your own driver, it is suggested to copy the HAL layer to your own code and keep them until manual update.
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