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MMA8452 no I2C comms

Question asked by Adam Karkowski on May 10, 2016



I'm trying to get an MMA8452 working with a small 8-bit micro (8051 based). I'm bit-banging the I2C interface but the MMA8452 never responds. Looking at the scope, the comms frequency is about 60 kHz which the sensor should support.


Whenver I send the address (0x1D), I never get an ACK. If I ignore this and attempt to get a reading (e.g. from WHO_AM_I register) I always get 0xFF back meaning the device does not respond. I can scope the I2C lines and they look OK.


The procedure I'm using is (complete c file is attached).

// Start


    // Slave address


    // Slave control byte


     // Start


    // Slave address + read

  I2C_WRITE(TARGET | 0x80);

    // Read

    inData = I2C_READ();


VDD and VDDIO are definitely connected to 3V. Is there anything wrong with this? I really need an answer quickly so please respond as soon as you are able. If there is anything else you need to know, then please ask.

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