1 sensor per nRF51288.
Sensor supports either 400kHz I2C (10k pull up recommended) or SPI (2MHz typ, Max 20 MHz)
From the nRF51288 Product Specification:
Run current for SPI master at 4 Mbps. 200 μA
Run current for TWI at 400 kbps. 400 μA
So the run current for I2C is more than double and it is also slower, thus longer on.. right?
Is there anything else that could influence the power usage? (Power on/off etc.) Or can I safely say:
SPI uses less power than I2C?
What does HW/SW controlled mean?