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How to generate repeated start on I2C MC1322x

Question asked by Fabrice TOCCI on Feb 25, 2014
Latest reply on Feb 25, 2014 by Fabrice TOCCI


We are building a solution with MMA8451Q accelerometer and MC1322x.

I2C bus is used between 8451 and 1322.


I’m having problems reading MMA8451 registers.


When I attempt reading 8451 WHO I AM register (address 0x0D), I always go a wrong value (different from 0x1A).


I had a look to Freescale community and I found that a repeated Start method must be used to read 8451 registers (

I thought I was using this method when transfer mode is set to gI2cMstrHoldBus_c in the I2c_senddata function call.


What I discovered is that frame sent on I2C bus is the same if I use gI2cMstrHoldBus_c or gI2cMstrReleaseBus_c I2C transfer Modes. (see attached images)

Which function or Option Should I use to generate a repeated  Start?


Best regards.

Fabrice Tocci

SW engineer at Beenetic Systems.