Waspmote Stack EEPROM

The class WaspStackEEPROM has been developed to allow saving frames into the EEPROM memory instead of the SD card.

There two types of stack configuration:

• LIFO stack (last input, first output). This means that when we extract data, the most recently stored information will be provided first.

• FIFO stack (first input, first output). In this case, data is extracted in the same order as they were inserted inside the stack.

The user may find it interesting for storing, for example, frames which could not be delivered: if even after several retries, the communication was not successful, we can store data in the stack in order to send it next time Waspmote wakes up.

Another use would be to store frames which we want to send in the future; this is great for decreasing the use of the communication module, and saving battery.

A complete example of the functions: www.development.libelium.com/ut-06-stack-eeprom-basic-operation

Waspmote Files

WaspStackEEPROM.h ; WaspStackEEPROM.cpp

Constructor

To start using the Waspmote StackEEPROM library, an object from class WaspStackEEPROM must be created. This object, called stack, is created inside the Waspmote StackEEPROM library.

When calling this constructor, the block_size variable is initialized to BLOCK_SIZE constant. Also, _mode variable is set to the default stack mode LIFO_MODE.

Pre-Defined Constants

There are some constants defined in 'WaspStackEEPROM.h' used to limit the stack area and the size of each block inside the stack.

START_STACK → First position of the stack into the EEPROM. Must be greater than 1023.

END_STACK → Last position of the stack into the EEPROM. Max value is 4095.

BLOCK_SIZE → It fixes the size of each block inside the EEPROM. Max value is 255.

Figure: EEPROM memory map with stack detail

Initializing the stack

This function cleans the stack area writing 0xFF in each memory position. Also, it initializes the stack counter to 0 and the Front Pointer and Back Pointer of the stack. It is possible to choose the stack mode as input: LIFO_MODE or FIFO_MODE. By default, LIFO configuration is used. It returns \'1\' if success and \'0\' if error.

Example of use:

{
    // Possibility 1: Initialize stack (LIFO mode by default)
    stack.initStack();
    // Possibility 2: Initialize with LIFO mode
    stack.initStack( LIFO_MODE );
    // Possibility 3: Initialize with FIFO mode
    stack.initStack( FIFO_MODE );
}

It returns nothing.

Initializing the block size

Before using the stack it\'s mandatory to initialize the block size. With the function initBlockSize(), the user can define the block size. By default, the block size has the value of BLOCK_SIZE constant. It returns nothing. Each block includes one byte to indicate the length of the data and the rest of the block can be used for data.

Example of use:

{
    // Sets the block size to 100 Bytes
    stack.initBlockSize(100);
}

Push

To store a block of data into the stack, the push() function must be used. The size of the block must be lower than block_size. The required are: a vector of data to store and the vector length. The vector of data must be uint8_t type.

It returns:

• \'1\' on success

• \'0\' error writing

• \'2\' is full

• \'3\' block size small.

Example of use:

{
    // Pushes a frame into the stack
    stack.push(frame.buffer, frame.length);
}

Pop

The pop() function extracts a block of data previously stored into the stack. The function requires a pointer to a vector to store the extracted data.

It returns:

• \'0\' if empty

• \'1\' error reading

• \'2\' if error updating the new pointer

• Positive value, except 1 or 2, means the number of bytes read

Example of use:

{
    // Extracts a frame from the stack
    frame.length = stack.pop(frame.buffer);
}