How to send and received data from external accessory asynchronize

Question

I am confused about send and received data from external accessory asynchronized way. I use MFi External Accessory, I checked EADemo, but seems that send and received data synchronized way. Any suggestions about this, thanks in advance.

Answer 1

First of all you have to attach input/output streams to a runLoop:

[[session inputStream] scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[[session inputStream] open];
[[session outputStream] scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[[session outputStream] open];

Become their delegate:

[[session outputStream] setDelegate:self];
[[session inputStream] setDelegate:self];

Once you become delegate you have to implement this method:

-(void)stream:handleEvent:{};

Here is an example:

-(void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)_event {
    switch (_event)
    {
        case NSStreamEventHasBytesAvailable:
            /* This part will be executed every time your rx buffer contains at least 1 byte */
            switch(state) {
                uint8_t ch;
                /* Read byte per byte */
                [stream read:&ch maxLength:1];
                /* now ch contains a byte from your MFI device
                ** and 'read' function decrease the length of the rx buffer by -1 */
            }
            break;
    }
}

This is the command to write out data to a stream:

/* txQueue is a NSData containing data to transmit. */
[[session outputStream] write:(uint8_t *)[txQueue bytes] maxLength:[txQueue length]];