HAL

Collaboration diagram for HAL:

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Detailed Description

Hardware Abstraction Layer.

Under ChibiOS/RT the set of the various device driver interfaces is called the HAL subsystem: Hardware Abstraction Layer. The HAL is the abstract interface between ChibiOS/RT application and hardware.

HAL Device Drivers Architecture

A device driver is usually split in two layers:

• High Level Device Driver (HLD). This layer contains the definitions of the driver's APIs and the platform independent part of the driver.
  An HLD is composed by two files:
  • <driver>.c, the HLD implementation file. This file must be included in the Makefile in order to use the driver.
  • <driver>.h, the HLD header file. This file is implicitly included by the HAL header file hal.h.
• Low Level Device Driver (LLD). This layer contains the platform dependent part of the driver.
  A LLD is composed by two files:
  • <driver>_lld.c, the LLD implementation file. This file must be included in the Makefile in order to use the driver.
  • <driver>_lld.h, the LLD header file. This file is implicitly included by the HLD header file.
  The LLD may be not present in those drivers that do not access the hardware directly but through other device drivers, as example the MMC_SPI driver uses the SPI and PAL drivers in order to implement its functionalities.

Diagram

Modules
	Configuration
	HAL Driver Configuration.
	Abstract I/O Channels
	Abstract I/O Block Device
	MMC/SD Block Devices common ancestor
	HAL Driver
	Hardware Abstraction Layer.
	PAL Driver
	I/O Ports Abstraction Layer.
	SPI Driver
	Generic SPI Driver.
	Serial Driver
	Generic Serial Driver.