microbit-dal/source/MicroBit.cpp

#include "MicroBit.h"

char MICROBIT_BLE_DEVICE_NAME[] = "BBC MicroBit [xxxxx]";
const char MICROBIT_BLE_MANUFACTURER[] = "The Cast of W1A";
const char MICROBIT_BLE_MODEL[] = "Microbit SB2";
const char MICROBIT_BLE_SERIAL[] = "SN1";
const char MICROBIT_BLE_HARDWARE_VERSION[] = "0.2";
const char MICROBIT_BLE_FIRMWARE_VERSION[] = "1.1";
const char MICROBIT_BLE_SOFTWARE_VERSION[] = "1.0";

/**
  * custom function for panic for malloc & new due to scoping issue.
  */
void panic(int statusCode)
{
    uBit.panic(statusCode);   
}

/**
  * Callback when a BLE GATT disconnect occurs.
  */
void bleDisconnectionCallback(Gap::Handle_t handle, Gap::DisconnectionReason_t reason)
{
    uBit.ble->startAdvertising(); // restart advertising!
}

/**
  * Constructor. 
  * Create a representation of a MicroBit device as a global singleton.
  * @param messageBus callback function to receive MicroBitMessageBus events.
  *
  * Exposed objects:
  * @code 
  * uBit.systemTicker; //the Ticker callback that performs routines like updating the display.
  * uBit.MessageBus; //The message bus where events are fired.
  * uBit.display; //The display object for the LED matrix.
  * uBit.buttonA; //The buttonA object for button a.
  * uBit.buttonB; //The buttonB object for button b.
  * uBit.buttonAB; //The buttonAB object for button a+b multi press.  
  * uBit.resetButton; //The resetButton used for soft resets.
  * uBit.accelerometer; //The object that represents the inbuilt accelerometer
  * uBit.compass; //The object that represents the inbuilt compass(magnetometer)
  * uBit.io.P*; //Where P* is P0 to P16, P19 & P20 on the edge connector
  * @endcode
  */
MicroBit::MicroBit() : 
    flags(0x00),
    i2c(MICROBIT_PIN_SDA, MICROBIT_PIN_SCL),
    serial(USBTX, USBRX),
    MessageBus(),
    display(MICROBIT_ID_DISPLAY, MICROBIT_DISPLAY_WIDTH, MICROBIT_DISPLAY_HEIGHT),
    buttonA(MICROBIT_ID_BUTTON_A,MICROBIT_PIN_BUTTON_A),
    buttonB(MICROBIT_ID_BUTTON_B,MICROBIT_PIN_BUTTON_B),
    buttonAB(MICROBIT_ID_BUTTON_AB,MICROBIT_ID_BUTTON_A,MICROBIT_ID_BUTTON_B), 
    accelerometer(MICROBIT_ID_ACCELEROMETER, MMA8653_DEFAULT_ADDR),
    compass(MICROBIT_ID_COMPASS, MAG3110_DEFAULT_ADDR),
    io(MICROBIT_ID_IO_P0,MICROBIT_ID_IO_P1,MICROBIT_ID_IO_P2,
       MICROBIT_ID_IO_P3,MICROBIT_ID_IO_P4,MICROBIT_ID_IO_P5,
       MICROBIT_ID_IO_P6,MICROBIT_ID_IO_P7,MICROBIT_ID_IO_P8,
       MICROBIT_ID_IO_P9,MICROBIT_ID_IO_P10,MICROBIT_ID_IO_P11,
       MICROBIT_ID_IO_P12,MICROBIT_ID_IO_P13,MICROBIT_ID_IO_P14,
       MICROBIT_ID_IO_P15,MICROBIT_ID_IO_P16,MICROBIT_ID_IO_P19,
       MICROBIT_ID_IO_P20)
{   
}

/**
  * Post constructor initialisation method.
  * After *MUCH* pain, it's noted that the BLE stack can't be brought up in a 
  * static context, so we bring it up here rather than in the constructor.
  * n.b. This method *must* be called in main() or later, not before.
  *
  * Example:
  * @code 
  * uBit.init();
  * @endcode
  */
void MicroBit::init()
{   
    //add the display to the systemComponent array
    addSystemComponent(&uBit.display);
    
    //add the compass and accelerometer to the idle array
    addIdleComponent(&uBit.accelerometer);
    addIdleComponent(&uBit.compass);

    // Seed our random number generator
    seedRandom();

#ifndef NO_BLE
    // Start the BLE stack.        
    ble = new BLEDevice();
    
    ble->init();
    ble->onDisconnection(bleDisconnectionCallback);
 
    // Add our auxiliary services.
    ble_firmware_update_service = new MicroBitDFUService(*ble);
    ble_device_information_service = new DeviceInformationService(*ble, MICROBIT_BLE_MANUFACTURER, MICROBIT_BLE_MODEL, MICROBIT_BLE_SERIAL, MICROBIT_BLE_HARDWARE_VERSION, MICROBIT_BLE_FIRMWARE_VERSION, MICROBIT_BLE_SOFTWARE_VERSION);
    ble_event_service = new MicroBitEventService(*ble);
    
    // Compute our auto-generated MicroBit device name.
    ble_firmware_update_service->getName(MICROBIT_BLE_DEVICE_NAME+14);
    
    // Setup advertising.
    ble->accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED | GapAdvertisingData::LE_GENERAL_DISCOVERABLE);
    ble->accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LOCAL_NAME, (uint8_t *)MICROBIT_BLE_DEVICE_NAME, sizeof(MICROBIT_BLE_DEVICE_NAME));
    ble->setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
    ble->setAdvertisingInterval(Gap::MSEC_TO_ADVERTISEMENT_DURATION_UNITS(1000));
    ble->startAdvertising();  
#else
    ble = NULL;
    ble_firmware_update_service = NULL;
    ble_device_information_service = NULL;
    ble_event_service = NULL;
#endif

    // Start refreshing the Matrix Display
    systemTicker.attach(this, &MicroBit::systemTick, MICROBIT_DISPLAY_REFRESH_PERIOD);     
}

/**
  * Delay for the given amount of time.
  * If the scheduler is running, this will deschedule the current fiber and perform
  * a power efficent, concurrent sleep operation.
  * If the scheduler is disabled or we're running in an interrupt context, this
  * will revert to a busy wait. 
  *
  * @note Values of 6 and below tend to lose resolution - do you really need to sleep for this short amount of time?
  * 
  * @param milliseconds the amount of time, in ms, to wait for. This number cannot be negative.
  *
  * Example:
  * @code 
  * uBit.sleep(20); //sleep for 20ms
  * @endcode
  */
void MicroBit::sleep(int milliseconds)
{
    //sanity check, we can't time travel... (yet?)
    if(milliseconds < 0)
        return;
        
    if (flags & MICROBIT_FLAG_SCHEDULER_RUNNING)
        fiber_sleep(milliseconds);
    else
        wait_ms(milliseconds);
}


/**
  * Generate a random number in the given range.
  * We use a simple Galois LFSR random number generator here,
  * as a Galois LFSR is sufficient for our applications, and much more lightweight
  * than the hardware random number generator built int the processor, which takes
  * a long time and uses a lot of energy.
  *
  * KIDS: You shouldn't use this is the real world to generte cryptographic keys though... 
  * have a think why not. :-)
  *
  * @param max the upper range to generate a number for. This number cannot be negative
  * @return A random, natural number between 0 and the max-1. Or MICROBIT_INVALID_VALUE (defined in ErrorNo.h) if max is <= 0.
  *
  * Example:
  * @code 
  * uBit.random(200); //a number between 0 and 199
  * @endcode
  */
int MicroBit::random(int max)
{
    //return MICROBIT_INVALID_VALUE if max is <= 0...
    if(max <= 0)
        return MICROBIT_INVALID_VALUE;
    
    // Cycle the LFSR (Linear Feedback Shift Register).
    // We use an optimal sequence with a period of 2^32-1, as defined by Bruce Schneider here (a true legend in the field!), 
    // For those interested, it's documented in his paper:
    // "Pseudo-Random Sequence Generator for 32-Bit CPUs: A fast, machine-independent generator for 32-bit Microprocessors"
    
    randomValue = ((((randomValue >> 31) ^ (randomValue >> 6) ^ (randomValue >> 4) ^ (randomValue >> 2) ^ (randomValue >> 1) ^ randomValue) & 0x0000001) << 31 ) | (randomValue >> 1);   
    return randomValue % max;
}


/**
  * Seed our a random number generator (RNG).
  * We use the NRF51822 in built cryptographic random number generator to seed a Galois LFSR.
  * We do this as the hardware RNG is relatively high power, and use the the BLE stack internally,
  * with a less than optimal application interface. A Galois LFSR is sufficient for our
  * applications, and much more lightweight.
  */
void MicroBit::seedRandom()
{
    randomValue = 0;
        
    // Start the Random number generator. No need to leave it running... I hope. :-)
    NRF_RNG->TASKS_START = 1;
    
    for(int i = 0; i < 4 ;i++)
    {
        // Clear the VALRDY EVENT
        NRF_RNG->EVENTS_VALRDY = 0;
        
        // Wait for a number ot be generated.
        while ( NRF_RNG->EVENTS_VALRDY == 0);
        
        randomValue = (randomValue << 8) | ((int) NRF_RNG->VALUE);
    }
    
    // Disable the generator to save power.
    NRF_RNG->TASKS_STOP = 1;
}


/**
  * Periodic callback. Used by MicroBitDisplay, FiberScheduler and buttons.
  */
void MicroBit::systemTick()
{   
    // Scheduler callback. We do this here just as a single timer is more efficient. :-)
    if (uBit.flags & MICROBIT_FLAG_SCHEDULER_RUNNING)
        scheduler_tick();  
    
    //work out if any idle components need processing, if so prioritise the idle thread
    for(int i = 0; i < MICROBIT_IDLE_COMPONENTS; i++)
        if(idleThreadComponents[i] != NULL && idleThreadComponents[i]->isIdleCallbackNeeded())
        {
            fiber_flags |= MICROBIT_FLAG_DATA_READ;
            break;
        }
        
    //update any components in the systemComponents array
    for(int i = 0; i < MICROBIT_SYSTEM_COMPONENTS; i++)
        if(systemTickComponents[i] != NULL)
            systemTickComponents[i]->systemTick();
}

/**
  * System tasks to be executed by the idle thread when the Micro:Bit isn't busy or when data needs to be read.
  */
void MicroBit::systemTasks()
{   
    //call the idleTick member function indiscriminately 
    for(int i = 0; i < MICROBIT_IDLE_COMPONENTS; i++)
        if(idleThreadComponents[i] != NULL)
            idleThreadComponents[i]->idleTick();
    
    fiber_flags &= ~MICROBIT_FLAG_DATA_READ;
}

/**
  * add a component to the array of components which invocate the systemTick member function during a systemTick 
  * @note this will be converted into a dynamic list of components
  */
void MicroBit::addSystemComponent(MicroBitComponent *component)
{
    int i = 0;
    
    while(systemTickComponents[i] != NULL && i < MICROBIT_SYSTEM_COMPONENTS)  
        i++;
    
    if(i == MICROBIT_SYSTEM_COMPONENTS)
        return;
        
    systemTickComponents[i] = component;    
}

/**
  * remove a component from the array of components
  * @note this will be converted into a dynamic list of components
  */
void MicroBit::removeSystemComponent(MicroBitComponent *component)
{
    int i = 0;
    
    while(systemTickComponents[i] != component  && i < MICROBIT_SYSTEM_COMPONENTS)  
        i++;
    
    if(i == MICROBIT_SYSTEM_COMPONENTS)
        return;

    systemTickComponents[i] = NULL;
}

/**
  * add a component to the array of components which invocate the systemTick member function during a systemTick 
  * @note this will be converted into a dynamic list of components
  */
void MicroBit::addIdleComponent(MicroBitComponent *component)
{
    int i = 0;
    
    while(idleThreadComponents[i] != NULL && i < MICROBIT_IDLE_COMPONENTS)  
        i++;
    
    if(i == MICROBIT_IDLE_COMPONENTS)
        return;
        
    idleThreadComponents[i] = component;    
}

/**
  * remove a component from the array of components
  * @note this will be converted into a dynamic list of components
  */
void MicroBit::removeIdleComponent(MicroBitComponent *component)
{
    int i = 0;
    
    while(idleThreadComponents[i] != component  && i < MICROBIT_IDLE_COMPONENTS)  
        i++;
    
    if(i == MICROBIT_IDLE_COMPONENTS)
        return;

    idleThreadComponents[i] = NULL;
}

/**
  * Determine the time since this MicroBit was last reset.
  *
  * @return The time since the last reset, in milliseconds. This will result in overflow after 1.6 months.
  * TODO: handle overflow case.
  */
unsigned long MicroBit::systemTime()
{
    return ticks;
}

/**
  * Triggers a microbit panic where an infinite loop will occur swapping between the panicFace and statusCode if provided.
  * 
  * @param statusCode the status code of the associated error. Status codes must be in the range 0-255.
  */
void MicroBit::panic(int statusCode)
{
    //show error and enter infinite while
    uBit.display.error(statusCode);
}