The maximum clock frequency in IMU fast mode is 400 kHz.
Reading LSM6DS3.cpp:165, readRegisterRegion()
is the same as the method described in “6.3.1 I2C operation” in the datasheet.
I can’t analyze further how much overhead there is because the IMU is under the can, so I can’t access the I2C pins.
When compiled with mbed, it is 600uS, but when compiled with non-mbed, it is 400uS. This may be usable.