6.9. NVRAM-Handler

The nvramhandler module is part of the Engine layer.

The nvramhandler module provides an interface to store or read data in the non-volatile memory. The data can either by stored cyclic (i.e. every 120s) or triggered (i.e. when opening the contacors while current is floating). The nvramhandler module is an abstraction layer to the actual implementation of the non-volatile ram (i.e. EEPROM or memory card).

6.9.1. Module Files

  • embedded-software\mcu-primary\src\engine\nvramhandler\nvramhandler.c (nvramhandler.c)
  • embedded-software\mcu-primary\src\engine\nvramhandler\nvramhandler.h (nvramhandler.h)
Driver Configuration:

6.9.2. Structure

The struct NVRAM_BLOCK_s contains the definition of an data block that is
stored in the non-volatile ram..
typedef struct NVRAM_BLOCK {
    NVRAM_state_e state;                /*!< state of datahandler block          */
    uint32_t lastUpdate;                /*!< time of last nvram update           */
    NVRAM_UpdateType_e mode;            /*!< update mode (cyclic or triggered)   */
    uint32_t updateCycleTime_ms;        /*!< cycle time of algorithm             */
    uint32_t phase_ms;                  /*!< start time when executing algorithm */
    STD_RETURN_TYPE_e (*funcRD)(void);  /*!< read callback function              */
    STD_RETURN_TYPE_e (*funcWR)(void);  /*!< write callback function             */

state contains the current state of the nvramhandler:

typedef enum NVRAM_state {
    NVRAM_wait    = 0,
    NVRAM_write   = 1,
    NVRAM_read    = 2,
} NVRAM_state_e;

Each block should be configured with the state NVRAM_wait. lastUpdate holds the timestamp when the data block was updated (written) the last time. mode is either NVRAM_Cyclic or NVRAM_Triggered. updateCycleTime_ms is the cyclic update time of the data block when configured in cyclic mode. phase_ms is a constant timing offset to prevent multiple write/read requests to the non-volatile storage at the same time. (*funcRD)(void)/(*funcWR)(void) is the callback pointer to the specific read/write function of the data block which are dependent on the specific implementation of the non-volatile ram.

The function NVRAM_dataHandlerInit intializes the struct NVRAM_BLOCK_s nvram_dataHandlerBlocks. It sets all states to NVRAM_wait and the lastUpdate to 0.

NVRAM_dataHandler loops over the different data blocks and updates the respective datablocks if either the cycle time is elapsed or a trigger has been received via the function NVRAM_setWriteRequest(NVRAM_BLOCK_ID_TYPE_e blockID). If a block is configured in cyclic mode it can still be triggered. It is then updated after receiving the trigger and afterwards again is updated every updateCycleTime_ms. Furthermore the function NVRAM_dataHandler can execute asynchronous read requests from the non-volatile storage over the function NVRAM_setReadRequest(NVRAM_BLOCK_ID_TYPE_e blockID).

NVRAM_BLOCK_ID_TYPE_e blockID is used to indicate which data block should be accessed. This implementation structure is analog the implementation of the database.


Defines are mapped to the enum and the enum corresponds to the order of the configured non-volatile data blocks in strcut NVRAM_BLOCK_s nvram_dataHandlerBlocks.