peripheral.sendData very slow if NSData is larger than a few bytes

[matthewkrueger]

Hi there - love the library so far.

Using the example application, I have been experimenting with reading a file to NSData, then sending the NSData using the "sendData" method.

However, if the NSData I'm sending is even a few KB, the transmission takes a very, very long time. For a 250KB NSData, I'm seeing times around 1-1.5 minutes to do the transfer. Am I doing something wrong, or is this a limitation of the library? Thanks!

[rhummelmose]

Unfortunately you'll find that this is a limitation of Bluetooth LE, spiced up by further limitations applied by iOS to the throughput available to each application :)

[matthewkrueger]

That's unfortunate. Is a transfer time of 1-1.5 minutes for 250KB of data in line with what you've seen in the past? I tried slowly increasing the size of my file and it seems the slowdown is linear, so I don't think I'm doing anything especially wrong. Thanks for the fast reply, much appreciated!

[rhummelmose]

Unfortunately, that sounds like very reasonable throughput. In previous iOS versions this was way worse. My suggestion would be to place the resource on some external location using a network connection and passing an address for it using the Bluetooth link. Of course I don't know your use-case so I'm just guessing away.

[matthewkrueger]

Unfortunately, the use-case requires transferring a binary file from a device with BLE but no internet connection to an iOS device, and THEN uploading the binary file to the web using the iOS device's internet connection. Doing a proof of concept using an iPad as the peripheral and iPhone as the central, so I have to pretend like the iPad has no network connection. Sounds like I'll have to temper the expectations for the transfer speed.

Thanks a lot for the insight and the great library, and especially the functional example project, much appreciated!

[rhummelmose]

You're welcome. Feel free to ask again.