Spurious data due to unnecessary call to [peripheral readValueForCharacteristic:characteristic]

[gene-pavlovsky]

Hello there,

I used your code as a base for writing a little test program for a different device that also has an accelerometer.
When I dumped the data to stdout, it looked a bit strange. While shaking the device, for every 3 realistic looking samples there was one sample with all zeros.

I tracked it down to this:
CBMicroBitBridge.mm, didUpdateValueForCharacteristic method does a call to [peripheral readValueForCharacteristic:characteristic]. I believe this is wrong.

The doc for didUpdateValueForCharacteristic says:

Core Bluetooth invokes this method when your app calls the readValueForCharacteristic: method. A peripheral also invokes this method to notify your app of a change to the value of the characteristic for which the app previously enabled notifications by calling setNotifyValue:forCharacteristic:.

Since your code uses notifications, there is no need to call readValueForCharacteristic manually. And doing that seems to be causing issues somehow. After I removed this call, I'm not getting all-zeros samples anymore. You might want to add && !error in the if condition as well, although I was not getting errors, just all-zeros samples.

Best regards
Gene