Peripheral.m

- (void)sendData:(NSData *)sendMsg
       dataIndex:(NSInteger)sendMsgIndex {
    // First up, check if we're meant to be sending an EOM
    static BOOL sendingEOM = NO;
    NSString *logMessage = nil;

    const int NOTIFY_MTU = 20;
    const float SendMessageTimeInterval = 0.2f;

    if (sendingEOM) {
        sendingEOM = NO;
        return;
    }
         
    NSInteger sendMsgIndex = 0;
    BOOL didSend = YES;
    while (didSend) {
        // Make the next chunk
        // Work out how big it should be
        NSInteger amountToSend = sendMsg.length;

        // Can't be longer than 20 bytes
        if (amountToSend > NOTIFY_MTU) {
            amountToSend = NOTIFY_MTU;
        }

        // Copy out the data we want
        NSData *chunk = [NSData dataWithBytes:sendMsg.bytes+sendMsgIndex length:amountToSend];

        [NSThread sleepForTimeInterval:SendMessageTimeInterval];

        if (self.characteristicM == nil) {
            break;
        }

        didSend = [self.peripheralManager updateValue:chunk
                                    forCharacteristic:self.characteristicM
                                 onSubscribedCentrals:nil];

        if (didSend == NO) {
            return;
        }

        NSString *stringFromData = [[NSString alloc] initWithData:chunk encoding:NSUTF8StringEncoding];

        sendMsgIndex += amountToSend;
        if (sendMsgIndex >= sendMsg.length) {
          sendingEOM = NO;
          return;
        }
    }
}