microbit: added MicroBitStorage for Persistent data

Integrated simple 1K block buffer to host small amount of persistent
data and a 1K FLASH memory block located immediately below the FOTA/DFU
bootloader and APPDATA region that intended to hold core configuration
information, such as:

* BLE bonding information.
* Compass Calibration data.
* Thermometer Calibration data.

The block is resident at 0x0003B400 - 0x0003B800.

inc/MicroBit.h

@@ -36,6 +36,7 @@
 
 #include "MicroBitBLEManager.h"
 #include "MicroBitRadio.h"
+#include "MicroBitStorage.h"
 
 // MicroBit::flags values
 #define MICROBIT_FLAG_SCHEDULER_RUNNING         0x00000001

inc/MicroBitStorage.h

@@ -0,0 +1,74 @@
+#ifndef MICROBIT_STORAGE_H
+#define MICROBIT_STORAGE_H
+
+#include "mbed.h"
+#include "MicroBitBLEManager.h"
+#include "MicroBitCompass.h"
+
+#define MICROBIT_STORAGE_CONFIG_MAGIC       0xCAFECAFE
+
+struct BLESysAttribute
+{
+    uint32_t        magic;
+    uint8_t         sys_attr[8];
+};
+
+struct MicroBitConfigurationBlock
+{
+    uint32_t            magic;
+    BLESysAttribute     sysAttrs[MICROBIT_BLE_MAXIMUM_BONDS];
+    CompassSample       compassCalibrationData;
+    int                 thermometerCalibration;
+};
+
+
+/**
+  * Class definition for the MicroBitStorage class.
+  * This allows reading and writing of small blocks of data to FLASH memory.
+  */
+class MicroBitStorage
+{
+    public:
+
+    /*
+     * Default constructor.
+     */  
+    MicroBitStorage();  
+  
+    /*
+     * Writes the given number of bytes to the address specified.
+     * @param buffer the data to write.
+     * @param address the location in memory to write to.
+     * @param length the number of bytes to write.
+     * TODO: Write this one!
+     */  
+    int writeBytes(uint8_t *buffer, uint32_t address, int length);
+
+    /** 
+     * Method for erasing a page in flash.
+     * @param page_address Address of the first word in the page to be erased.
+     */
+    void flashPageErase(uint32_t * page_address);
+
+    /** 
+     * Method for writing a word of data in flash with a value.
+     
+     * @param address Address of the word to change.
+     * @param value Value to be written to flash.
+     */
+    void flashWordWrite(uint32_t * address, uint32_t value);
+
+    /*
+     * Reads the micro:bit's configuration data block from FLASH into a RAM buffer.
+     * @return a structure containing the stored data. 
+     */  
+    MicroBitConfigurationBlock *getConfigurationBlock();
+
+    /*
+     * Writes the micro:bit's configuration data block from FLASH into a RAM buffer.
+     * @return a structure containing the stored data. 
+     */  
+    int setConfigurationBlock(MicroBitConfigurationBlock *block);
+};
+
+#endif

source/CMakeLists.txt

@@ -32,6 +32,7 @@ set(YOTTA_AUTO_MICROBIT-DAL_CPP_FILES
     "MicroBitLightSensor.cpp"
     "RefCounted.cpp"
     "MemberFunctionCallback.cpp"
+    "MicroBitStorage.cpp"
     "ble-services/MicroBitBLEManager.cpp"
     "ble-services/MicroBitDFUService.cpp"
     "ble-services/MicroBitEventService.cpp"

source/MicroBitStorage.cpp

@@ -0,0 +1,129 @@
+/**
+  * Class definition for the MicroBitStorage class.
+  * This allows reading and writing of FLASH memory.
+  */
+
+#include "MicroBit.h"
+
+/*
+ * Default constructor
+ */
+MicroBitStorage::MicroBitStorage()
+{
+}
+
+/*
+ * Writes the given number of bytes to the address specified.
+ * TODO: Complete this function to provide an abstraction across SD and no SD builds.
+ *
+ * @param buffer the data to write.
+ * @param address the location in memory to write to.
+ * @param length the number of bytes to write.
+ */  
+int MicroBitStorage::writeBytes(uint8_t *buffer, uint32_t address, int length)
+{
+    (void) buffer;
+    (void) address;
+    (void) length;
+    
+    return MICROBIT_OK;
+}
+
+/** 
+ * Method for erasing a page in flash.
+ *
+ * @param page_address Address of the first word in the page to be erased.
+ */
+void MicroBitStorage::flashPageErase(uint32_t * page_address)
+{
+    // Turn on flash erase enable and wait until the NVMC is ready:
+    NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Een << NVMC_CONFIG_WEN_Pos);
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+
+    // Erase page:
+    NRF_NVMC->ERASEPAGE = (uint32_t)page_address;
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+
+    // Turn off flash erase enable and wait until the NVMC is ready:
+    NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos);
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+}
+
+
+/*
+ * Reads the micro:bit's configuration data block from FLASH into a RAM buffer.
+ * @return a pointer to the structure containing the stored data. 
+ * NOTE: it is the callers responsibility to free the buffer.
+ */  
+
+MicroBitConfigurationBlock *MicroBitStorage::getConfigurationBlock()
+{
+    uint32_t pg_size = NRF_FICR->CODEPAGESIZE;
+    uint32_t pg_num  = NRF_FICR->CODESIZE - 19;          // Use the page just below the BLE Bond Data 
+
+    MicroBitConfigurationBlock *block = new MicroBitConfigurationBlock();
+    memcpy(block, (uint32_t *)(pg_size * pg_num), sizeof(MicroBitConfigurationBlock));
+
+    if (block->magic != MICROBIT_STORAGE_CONFIG_MAGIC) 
+        memclr(block, sizeof(MicroBitConfigurationBlock));
+
+    return block;
+}
+
+/** 
+ * Function for filling a page in flash with a value.
+ *
+ * @param address Address of the first word in the page to be filled.
+ * @param value Value to be written to flash.
+ */
+void MicroBitStorage::flashWordWrite(uint32_t * address, uint32_t value)
+{
+    // Turn on flash write enable and wait until the NVMC is ready:
+    NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos);
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+
+    *address = value;
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+
+    // Turn off flash write enable and wait until the NVMC is ready:
+    NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos);
+
+    while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
+}
+
+
+/*
+ * Writes the micro:bit's configuration data block from FLASH into a RAM buffer.
+ * @return a structure containing the stored data. 
+ */  
+int MicroBitStorage::setConfigurationBlock(MicroBitConfigurationBlock *block)
+{
+    uint32_t * addr;
+    uint32_t   pg_size;
+    uint32_t   pg_num;
+    int   wordsToWrite = sizeof(MicroBitConfigurationBlock) / 4 + 1;
+    
+    pg_size = NRF_FICR->CODEPAGESIZE;
+    pg_num  = NRF_FICR->CODESIZE - 19;          // Use the page just below the BLE Bond Data 
+
+    addr = (uint32_t *)(pg_size * pg_num);
+
+    flashPageErase(addr);
+
+    uint32_t *b = (uint32_t *) block;
+
+    for (int i = 0; i < wordsToWrite; i++)
+    {
+        flashWordWrite(addr, *b);
+        addr++;
+        b++;
+    }
+
+    return MICROBIT_OK;
+}
+