Improve README and doxygen comments

README.md

@@ -1,8 +1,81 @@
-# Helpers
+# STA Core library
 
 Collection of useful stuff.
 
 
-## lang.hpp
 
-Macros related to compiler features. Not actually part of the language so renaming would be advised.
+# Modules
+
+
+## Assert
+
+Assertion handling.
+
+Configuration:
+* `#define STA_ASSERT_ENABLE`: Enable module
+* `#define STA_ASSERT_DISABLE`: Forces module off when defined
+* `#define STA_HALT <func_name>`: Override function called after failed asserts
+* `DEBUG`: Automatically enables module when defined
+* `NDEBUG`: Forces module off when defined
+
+Both `sta::assert_failed` and `sta::assert_halt` provide weak definitions and
+can be overridden by the application. `sta::assert_halt` is only called
+via the **STA_HALT** macro which can also be provided by the application.
+
+The default implementation of `sta::assert_failed` uses **STA_DEBUG_PRINT** internally
+and will not generate any output if the **DEBUG_SERIAL** module is disabled.
+
+
+## Debug Serial
+
+Debug serial output macros.
+
+Configuration:
+* `#define STA_DEBUG_SERIAL_ENABLE`: Enable module
+* `#define STA_DEBUG_SERIAL_DISABLE`: Forces module off when defined
+* `DEBUG`: Automatically enables module when defined
+* `NDEBUG`: Forces module off when defined
+
+The `sta::DebugSerial` instance must be provided.
+
+
+## Endian
+
+Endian-ness conversion for multi-byte types.
+
+
+## Enum Flags
+
+Type for using enum values as combinable flags.
+
+
+## Lang
+
+Macros related to compiler features. Not actually part of the C/C++ language.
+
+
+## MCU
+
+Defines specific to different MCUs. Include the appropriate header from `sta/mcu`
+for the MCU used by the application in the `<sta/config.hpp>` header. 
+
+
+## Printf
+
+Choose which `printf` implementation is used by STA libraries.
+
+Configuration:
+* `#define STA_PRINTF_USE_STDLIB`:  Use the stdlib implementation
+* `#define STA_PRINTF_USE_MPALAND`: Use the implementation by Marco Paland (thread safe & reentrant)
+
+
+## HAL Delay
+
+HAL based delay functions.
+
+Configuration:
+* `#define STA_HAL_DELAY_ENABLE`: Enable module
+* `#define STA_HAL_DELAY_US_TIM <tim_handle>`: 1 MHz TIM instance used by `sta::delayUs`
+
+TIM time base must be started before using `sta::delayUs` by calling `sta::initHAL`.
+When using the startup system task this is handled automatically.