/**
* Copies characters into the buffer used for Transmitting to the central device.
*
* @param buf a buffer containing length number of bytes.
* @param length the size of the buffer.
* @param mode the selected mode, one of: ASYNC, SYNC_SPINWAIT, SYNC_SLEEP. Each mode
* gives a different behaviour:
*
* ASYNC - Will copy as many characters as it can into the buffer for transmission,
* and return control to the user.
*
* SYNC_SPINWAIT - will return MICROBIT_INVALID_PARAMETER
*
* SYNC_SLEEP - Will perform a cooperative blocking wait until all
* given characters have been received by the connected
* device.
*
* @return the number of characters written, or MICROBIT_NOT_SUPPORTED if there is
* no connected device, or the connected device has not enabled indications.
*/
int MicroBitUARTService::send(const uint8_t *buf, int length, MicroBitSerialMode mode)
{
if(length < 1 || mode == SYNC_SPINWAIT)
return MICROBIT_INVALID_PARAMETER;
bool updatesEnabled = false;
ble.gattServer().areUpdatesEnabled(*txCharacteristic, &updatesEnabled);
if(!ble.getGapState().connected && !updatesEnabled)
return MICROBIT_NOT_SUPPORTED;
int bytesWritten = 0;
while(bytesWritten < length && ble.getGapState().connected && updatesEnabled)
{
for(int bufferIterator = bytesWritten; bufferIterator < length; bufferIterator++)
{
int nextHead = (txBufferHead + 1) % txBufferSize;
if(nextHead != txBufferTail)
{
txBuffer[txBufferHead] = buf[bufferIterator];
txBufferHead = nextHead;
bytesWritten++;
}
}
int size = txBufferedSize();
uint8_t temp[size];
memclr(&temp, size);
circularCopy(txBuffer, txBufferSize, temp, txBufferTail, txBufferHead);
if(mode == SYNC_SLEEP)
fiber_wake_on_event(MICROBIT_ID_NOTIFY, MICROBIT_UART_S_EVT_TX_EMPTY);
ble.gattServer().write(txCharacteristic->getValueAttribute().getHandle(), temp, size);
if(mode == SYNC_SLEEP)
schedule();
else
break;
ble.gattServer().areUpdatesEnabled(*txCharacteristic, &updatesEnabled);
}
return bytesWritten;
}
/**
* An internal method to configure an interrupt on tx buffer and also
* a best effort copy operation to move bytes from a user buffer to our txBuff
*
* @param string a pointer to the first character of the users' buffer.
*
* @param len the length of the string, and ultimately the maximum number of bytes
* that will be copied dependent on the state of txBuff
*
* @param mode determines whether to configure the current fiber context or not. If
* The mode is SYNC_SPINWAIT, the context will not be configured, otherwise
* no context will be configured.
*
* @return the number of bytes copied into the buffer.
*/
int MicroBitSerial::setTxInterrupt(uint8_t *string, int len, MicroBitSerialMode mode)
{
int copiedBytes = 0;
for(copiedBytes = 0; copiedBytes < len; copiedBytes++)
{
uint16_t nextHead = (txBuffHead + 1) % txBuffSize;
if(nextHead != txBuffTail)
{
this->txBuff[txBuffHead] = string[copiedBytes];
txBuffHead = nextHead;
}
else
break;
}
if(mode != SYNC_SPINWAIT)
fiber_wake_on_event(MICROBIT_ID_NOTIFY, MICROBIT_SERIAL_EVT_TX_EMPTY);
//set the TX interrupt
attach(this, &MicroBitSerial::dataWritten, Serial::TxIrq);
return copiedBytes;
}
