i2c_on_board_accelerometer_KL25Z reference : https://github.com/alexander-g-dean/ESF/blob/master/Code/Chapter_8/I2C-Demo/src/i2c.c http://www.microdigitaled.com/ARM/Freescale_ARM/Code/Ver1/Chapter9/Program9_3.txt https://www.nxp.com/docs/en/application-note/AN4342.pdf