Where am I supposed to get an I2C BUFFER_LENGTH defined? I am using a BLE nano - as soon as I try to include I2Cdev.h and compile, I get this error:

Arduino\libraries\I2Cdev\I2Cdev.cpp:276:62: error: 'BUFFER_LENGTH' was not declared in this scope


How should I fix this? I imagine I can hard-code it in and guess around as to the value (32 seems common), but I think I am missing something else as far as it using the right libraries for the hardware, so how can I check/fix that if it is indeed the case?
BUFFER_LENGTH is set in I2Cdev.h depending on the target. BLE nano is not directly supported (what I can see). 

Cheers!