altimeter - AVR code for an in-progress pressure altimeter

	Commit message (Collapse)	Author	Age
*	Use more generic interface for barometer and timer	David Phillips	2021-02-27
\| \| \| \| \| \| \| \| \| \| \|	This patch abstracts the global symbols for getting barometer readings behind a "struct of function pointers" interface as popular in Linux Kernel, U-Boot and others. This means that unit testing can take place with mocked hardware peripherals. The old "global" drivers are still available, behind explicit function calls required to access the now-static functions. This patch also introduces a timer peripheral software module with the same model, to support future unit testing of altitude rate etc.
*	Implement barometer reset/init	David Phillips	2021-02-14
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*	Initial prototype	David Phillips	2020-12-13
	This patch adds a skeleton of AVR code for a "simulator" target (atmega2560) and for the real intended hardware target (atmega32u4). The simulator target is one that is supported by the QEMU AVR emulator, while the 32u4 is currently not.