Another full update of current work

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diff --git a/docs/add_support.md b/docs/add_support.md
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diff --git a/docs/index.md b/docs/index.md
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+AVR Input/Output expansion
+==========================
+
+Modules
+-------
+| Module                        | Header   | Enable Config                             | Description                                            |
+|-------------------------------|----------|-------------------------------------------|--------------------------------------------------------|
+| [IO Ports](modules/ioport.md) | ioport.h | CONFIG_IOPORTS and CONFIG_IOE_PCINTERRUPT | Simple input/output port access                        |
+| [SPI](modules/spi.md)         | spi.h    | CONFIG_SPI                                | Serial peripheral interface                            |
+| [USART](modules/usart.md)     | usart.h  | CONFIG_USART                              | Universal synchronous/asynchronous receive/transmitter |
diff --git a/docs/modules/ioport.md b/docs/modules/ioport.md
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+IO port
+=======
+To use include: `ioport.md`  
+And define: `CONFIG_IOE_IOPORT`
+
+Defines simple access to io ports. This allows runtime access to any pin with just
+serialized identifier.
+
+Most of the functions has group and mask arguments. Group is letter, but in this
+library is represented as number and exact number is defined as macro definition.
+Mask is one shifted by index number(use \_BV macro). This way can be
+addressed all IO ports. Exact identification consult with datasheet. You can also
+use more than one index number and control more ports in single group with single
+command.
+
+WARNING: No check is implemented for right group number. Usage of unsupported
+value is undefined (write to other parts of memory can happen).
+
+## References
+### For output
+#### Function io_setout
+```C
+static inline void io_setout(uint8_t group, uint8_t mask)
+```
+Configures port of `group` with `mask` as output.  
+Parameters:
+    group - Character specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+#### Function io_hight
+```C
+static inline void io_hight(uint8_t group, uint8_t mask)
+```
+Sets output port to hight (also can be called as 1).  
+WARNING: Invoke this only if io_setout is called before.  
+Parameters:
+    group - Character specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+#### Function io_low
+```C
+static inline void io_low(uint8_t group, uint8_t mask)
+```
+Sets output port to low (also called as 0).  
+WARNING: Invoke this only if io_setout is called before.  
+Parameters:
+    group - Number specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+#### Function io_set
+```C
+static inline void io_set(uint8_t group, uint8_t mask, int8_t val)
+```
+Sets output port to value passed as argument.  
+WARNING: Invoke this only if io_setout is called before.  
+Parameters:
+    group - Number specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+### For input
+#### Function io_setin
+```C
+static inline void io_setin(uint8_t group, uint8_t mask,
+                                enum ioeIOInResistor resistor)
+```
+Configures port of `group` with `mask` as input with specified pull-up/down
+resistor.  
+Parameters:
+    group - Number specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+#### Function io_get
+```C
+static inline int8_t io_get(uint8_t group, uint8_t mask)
+```
+Returns current value of port. Note that you can use this also if port is
+configured as output.  
+Parameters:
+    group - Number specifying exact port group
+    mask  - Binary shifted 1. Shift is equal to port index in specified group.
+
+#### Enum ioeIOInResistor
+```C
+enum ioeIOInResistor {
+    IOE_IO_PULLUP,
+    IOE_IO_PULLDOWN
+};
+```
+This enum is used as argument for io_setin. Names should be self explanatory
+in this case.
+
+### Pin change interrupts
+#### Function io_change_sethook
+```C
+int8_t io_change_sethook(uint8_t group, uint8_t mask, uint8_t edge,
+                           void (*change) (uint8_t group, uint8_t mask))
+```
+Registers function `change` as hook for pin change interrupt. `group` and `mask`
+specifies port and edge specifies on what edge should hook be called. `edge` can
+be IO_RISING or IO_FALLING or their binary combination with operator
+`|`.  
+WARNING: `change` call is call during interrupt handling. You shouldn't be
+blocking execution for long time.  
+Parameters:  
+    group  - Number specifying exact port group
+    mask   - Binary shifted 1. Shift is equal to port index in specified group.
+    edge   - Signals on what edge should be hook called.
+    change - Pointer to function used as interupt hook
+
+#### Function io_change_remhook
+```C
+int8_t io_change_remhook(void (*change) (uint8_t group, uint8_t mask))
+```
+Removes `change` hook.  
+Parameters:  
+    change - Pointer to function used as hook
+
+### Others
+#### Definitions IO_{GROUP}
+This defines exact numbers related to data-sheet groups. Always use these
+definition not direct numbers, you can ensure cross MCU support this way.
+
+#### Definitions IO_{GROUP}{INDEX}
+Because specifying group and mask as separate parameters is not always optimal,
+mcu support file should define all ports in form of single line definition in
+format `IOE_IO_{GROUP}{INDEX}`. Disadvantage is that with these definitions you
+can't use binary conjunction and so only one pin can be controlled with it.
+
+## Relevant examples
+* blink
+* pcinterrupt
+
+## Adding support
+For more information on how add support, see `doc/add_support.md`.
+Main definition is `MCUSUPPORT_IOPORT`. Define it to enable support.
+
+### IO_{GROUP}
+This should define any number that is handy for implementation of `IOE_IOE_PIN`,
+`IOE_IO_DDR` and `IOE_IO_PORT`.
+
+### IO_{PIN/DDR/PORT}
+These should calculate exact pointers to register `PORT{GROUP}` for PORT variant
+and likewise for others with group as argument. Common implementation would be
+like this:
+```C
+#define IOE_IO_PIN(GROUP)  (* (volatile uint8_t *)(PINB + 0x3*GROUP))
+```
+### IO_{GROUP}{INDEX}
+This should be pair of group and one binary shifted to left relative to index.
+
+### MCUSUPPORT_PCINT{NUM}
+This defines that MCU supports specific pin change interrupt group. Also it
+defines value that is number of pins in group.
diff --git a/docs/modules/spi.md b/docs/modules/spi.md
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+Serial peripheral interface
+===========================
+This interface is link to MOSI and MISO pins. Also SS pin is used when slave mode initialized.
+
+## References
+### spi\_init
+```C
+static inline void spi_init(enum spiMode mode)
+```
+Initializes SPI interface.  
+Parameters:  
+    mode - Specify mode of SPI interface  
+  
+NOTE: Global interrupts must be enabled for right function of SPI.
+
+### spi\_busy
+```C
+static inline int8_t spi_busy(void)
+```
+Returns NULL when device is not busy.  
+When device is busy return values in non-zero.
+
+### spi\_join    
+```C
+static inline void spi_join(void)
+```
+Blocks processor until device is not busy.
+
+### spi\_send
+```C
+static inline uint8_t spi_send(uint8_t data)
+```
+Swap bytes with slave over SPI.  
+This function blocks execution until device isn't busy (transfer completed).  
+WARNING: Invoke this only when interface is initialized in MASTER mode.
+
+### spi\_transfer
+```C
+static inline void spi_transfer(uint8_t data)
+```
+Transfer byte to slave over SPI.  
+This function isn't blocking execution until transfer is complete.  
+Always call spi\_join before this function when called outside of spi\_receive().  
+WARNING: Invoke this only when interface is initialized in MASTER mode.
+
+### spi\_expose
+```C
+static inline void spi_expose(uint8_t data)
+```
+Expose data for next master request.
+Please don't use this when device is busy.
+Best place to call this is spi\_receive().  
+WARNING: Invoke this only when interface is initialized in SLAVE mode.
+
+## Function pointer spi\_receive
+```C
+extern void (*spi_receive)(uint8_t data)
+```
+This function is called every time transfer is finished.
+And until return from this function interrupts are disabled.
+
+## Enum spiMode
+```C
+enum spiMode {
+    SPI_MODE_MASTER,
+    SPI_MODE_SLAVE
+};
+```
+This is used as parameter for spi\_init function.
diff --git a/docs/modules/tasks.md b/docs/modules/tasks.md
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+Tasks
+=====
+Tasks allows separate jobs.
+
+## Functions
+### tasks_run
+```C
+int8_t tasks_run(void)
+```
+This function starts tasks execution. Should be called after all task slots are
+prepared and at least one task is started. This function exits if no task exist or
+all existing tasks exited.
+
+### task_init
+
+## Structures
+### Task
+```C
+typedef struct {
+    uint8_t flags;
+    void (*func) (void);
+} Task;
+```
+
+### TaskSlot
+```C
+typedef struct {
+    uint8_t flags;
+    Task *task;
+    uint8_t stack_size;
+    uint8_t stack[];
+} TaskSlot;
+```
+
+### Mutex
+
+### Semaphore
diff --git a/docs/modules/timer.md b/docs/modules/timer.md
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diff --git a/docs/modules/usart.md b/docs/modules/usart.md
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diff --git a/docs/modules/utils/buffer.md b/docs/modules/utils/buffer.md
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+buffer
+======
+In whole project are used ring buffers. This is so common that handling them is
+exported to separated header file. In fact it contains two implementations of
+buffers. One implementation is defined using preprocessor macros. Another one is
+plain C code.
+
+## Preprocessor implementation
+Preprocessor implementation is expected to be faster and less memory intense. Also
+more suitable for buffers of simple types (such us int). But this buffer has to be
+defined with known size at compile time and can't be resized. All this makes it
+good implementation for IO devices input and output buffers, but less for more
+complicated tasks containing for example sorting.
+
+### Macros
+#### IOEBUFFER
+```C
+IOEBUFFER(type, name, size)
+```
+This macro defines buffer. Use it to define new buffer.
+##### Parameters
+| type | Specify type of elements in buffer. Can be any valid C type |
+| name | Name of buffer. This is C variable name.                    |
+| size | Numerical value of buffer size                              |
+
+#### IOEBUFFER_INIT
+```C
+IOEBUFFER_INIT(name, size)
+```
+Use this to initialize buffer. Parameter `size` must be same as for IOEBUFFER
+(definition of buffer). You can use this also to reset buffer (remove all data
+from buffer).
+##### Parameters
+| name | Name if buffer. This is C variable name. |
+| size | Numerical value of buffer size           |
+
+#### IOEBUFFER_PUT
+```C
+IOEBUFFER_PUT(name, size, data, mode)
+```
+Use this macro to add new data to buffer.
+##### Parameters
+| name | Name of buffer. This is C variable name. |
+| size | Numerical value of buffer size           |
+| data | Data to be stored to buffer              |
+| mode | This specifies action if buffer is full. |
+##### Modes
+| IOEBUFFER_MODE_BLOCK     | Block execution until buffer has some free space. |
+| IOEBUFFER_MODE_OVERWRITE | Overwrites oldest added (fist to be read)         |
+| IOEBUFFER_MODE_DROP      | New data won't be stored to buffer if full        |
+
+#### IOEBUFFER_GET
+```C
+IOEBUFFER_GET(name, size, variable)
+```
+Get value from buffer. Value is stored in `variable` (it is variable of same type
+as buffer data, not pointer to variable of same type). If no data is in buffer,
+variable is set to NULL.
+##### Parameters
+| name     | Name of buffer. This is C variable name.  |
+| size     | Numerical value of buffer size.           |
+| variable | Variable in which data will be stored in. |
+
+#### IOEBUFFER_CNT
+```C
+IOEBUFFER_CNT(name, size, variable)
+```
+Counts number of data entries in buffer and saves value to variable.
+##### Parameters
+| name     | Name of buffer. This is C variable name.                    |
+| size     | Numerical value of buffer size.                             |
+| variable | Int/Unsigned type variable where data count will be stored. |
+
+## C implementation
+C implementation is more general. Size is defined by calling initialization
+function. But it is using general pointers, so it is only able store pointers.
+
+As buffer identification is used defined type `IOEBuffer`. All functions takes
+pointer to this type as parameter. Because of this, it won't be described for
+every function.
+
+### Functions
+#### ioebuffer_init
+```C
+int8_t ioebuffer_init(IOEBuffer *buf, uint8_t size, uint8_t flags)
+```
+Initialized buffer and allocates required resources.
+##### Parameters
+| size  | Number of elements to be maximally stored in buffer |
+| flags | TODO
+##### Flags
+TODO
+
+#### ioebuffer_uninit
+```C
+void ioebuffer_uninit(IOEBuffer *buf)
+```
+Frees all resources allocated during initialization of buffer. Use this every time
+you are freeing buffer.
+
+#### ioebuffer_put
+```C
+int8_t ioebuffer_put(IOEBuffer *buf, void *data)
+```
+Add `data` to buffer
diff --git a/docs/modules/utils/narray.md b/docs/modules/utils/narray.md
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+narray.h
+========
+This implements some helping functions for null terminated arrays. Null terminated
+arrays are used across whole project because they are simple and don't waste
+memory space.  Their disadvantage is more complicated implementation of utility
+functions and much longer adding time (they are reallocated every time new data
+are added).
+
+This implementation is limited to only contains 255 elements(limited by uint8_t
+type). But it should be enough for basic usage. If you need store more than that,
+you should use different approach. Also only pointers can be stored.
+
+To define null terminated array just define pointer to you required pointer and set
+it to NULL. Such narray is handled as empty. Example:
+```C
+int **narray = 0;
+```
+After adding some data (in example case data of type `int*`) you can access them
+same as if you would working with simple array (`narray[i]`). Last element it such
+array is `NULL`. No more valid data are stored after `NULL` (This also means that
+`NULL` can't be stored to narray).
+
+All functions are taking as parameter `void ***array`, which is pointer to null
+terminated array. This parameter won't be described in functions.
+
+## Functions and macros
+### narray_add
+```C
+void narray_add(void ***array, void *data)
+```
+Add data to end of the array. This increases size of the array by one (two bytes).
+#### Parameters
+| data | data to be stored to array |
+
+### narray_remove
+```C
+void narray_remove(void ***array, void *data)
+```
+Remove specified data from array. This effectively decreases size of the array by
+one (two bytes).
+#### Parameters
+| data | data to be removed from array |
+
+### narray_size
+```C
+size_t narray_size(void ***array)
+```
+Returns size of array.
+
+### narray_free
+```C
+inline void narray_free(void ***array)
+```
+Frees whole array if allocated.
+
+### fornarray
+```C
+#define fornarray(array, i, data) for (i = 0; (data = array[i]) != 0; i++)
+```
+This is macro. It implements simple foreach cycle.
+#### Parameters
+| array | array it self (void ** not pointer)        |
+| i     | unsigned integer (uint8_t)                 |
+| data  | variable which will be used to access data |
diff --git a/docs/usage.md b/docs/usage.md
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