Intro to the External Accessory Framework

Andrew Craze@AndrewCr

acraze at dxysolutions.com

Agenda•What is the EA Framework useful for?

•What hardware can I talk to?

•How do I use the EA Framework?

•Why/how do I get more info from Apple under the MFi NDA?

What can I do with EAAccessory?

•Application [not accessory] -side code

•Enumerate connected accessories

•Open a serial session with an accessory

•Communicate via streams and get notifications

What can’t I do with EAAccessory?

•Pair or make the connection with a BlueTooth device

•Use (any) BlueTooth profiles

Hardware Options•Consumer-ready (pre-built cables)

Like RedPark’s

•Build-your-own, with 3rd-party firmware

Like BlueGiga’s

•Build-your-own, with DIY firmware

Join the MFi program for Docs

Easier Hardware(Examples, probably not the only options)

RedPack’s Serial Cable BlueGiga’s iWrap Firmware

Application ChecklistLink with ExternalAccessory.framework

Add protocol(s) to info.plist

Use EAAccessoryManager to find your device

Add a delegate (EAAccessoryDelegate) to your accessory’s object

Connect with your chosen protocol

Manage the I/O stream data

Link with ExternalAccessory.framework

Add protocol(s) to info.plist

Use EAAccessoryManager to find your device

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_accessoryDidConnect:) name:EAAccessoryDidConnectNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_accessoryDidDisconnect:) name:EAAccessoryDidDisconnectNotification object:nil]; [[EAAccessoryManager sharedAccessoryManager] registerForLocalNotifications];

_accessoryList = [[NSMutableArray alloc] initWithArray:[[EAAccessoryManager sharedAccessoryManager] connectedAccessories]];

Add delegate to your accessory’s object, connect to streams

[_accessory setDelegate:self]; _session = [[EASession alloc] initWithAccessory:_accessory forProtocol:_protocolString];

if (_session) { [[_session inputStream] setDelegate:self]; [[_session inputStream] scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [[_session inputStream] open];

[[_session outputStream] setDelegate:self]; [[_session outputStream] scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [[_session outputStream] open]; } else { NSLog(@"creating session failed"); }

Manage the I/O stream data, part 1

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode{ switch (eventCode) { case NSStreamEventNone: break; case NSStreamEventOpenCompleted: break; case NSStreamEventHasBytesAvailable: [self _readData]; break; case NSStreamEventHasSpaceAvailable: [self _writeData]; break; case NSStreamEventErrorOccurred: break; case NSStreamEventEndEncountered: break; default: break; }}

Manage the I/O stream data, part 2

- (void)_readData {#define EAD_INPUT_BUFFER_SIZE 128 uint8_t buf[EAD_INPUT_BUFFER_SIZE]; while ([[_session inputStream] hasBytesAvailable]) { NSInteger bytesRead = [[_session inputStream] read:buf maxLength:EAD_INPUT_BUFFER_SIZE]; if (_readData == nil) { _readData = [[NSMutableData alloc] init]; } [_readData appendBytes:(void *)buf length:bytesRead]; //NSLog(@"read %d bytes from input stream", bytesRead); }

[[NSNotificationCenter defaultCenter] postNotificationName:EADSessionDataReceivedNotification object:self userInfo:nil];}

- (NSData *)readData:(NSUInteger)bytesToRead{ NSData *data = nil; if ([_readData length] >= bytesToRead) { NSRange range = NSMakeRange(0, bytesToRead); data = [_readData subdataWithRange:range]; [_readData replaceBytesInRange:range withBytes:NULL length:0]; } return data;}

The MFi Program•Separate NDA, over-and-above the

iOS developer program

•Free, but you must be a bona-fide company (and prove it!)

•Plan on a month to get fully-approved

•Docs on everything you need to know for accessory-side development

Handy reference links

(No endorsement expressed or implied. So there.)

• External Accessory Framework Reference (from Apple)http://developer.apple.com/library/ios/#documentation/ExternalAccessory/Reference/ExternalAccessoryFrameworkReference/_index.html#//apple_ref/doc/uid/TP40008235

• Apple’s EADemo sample codehttp://developer.apple.com/library/ios/#samplecode/EADemo/Introduction/Intro.html

• Apple MFi pagehttps://developer.apple.com/programs/mfi/

• Redpark Serial Cablehttp://redpark.com/c2db9.html

• BlueGiga’s iWrap firmware (for their BlueTooth modules)http://www.bluegiga.com/iWRAP_module_firmware

Questions, Maybe Answers

Andrew Craze

@AndrewCr

http://blog.andrewcraze.com

acraze at dxysolutions.com