How to read and write to registers of MMA7660 using TWI

[saiteja]

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Hi, i am working on TWI sensor example in SDK1. in which i connected SCL And SDA pins tonRF52 dk boards sca and scl pins. and connected voltage and ground. when i run the application on board i am getting x,y,z values and when i shake the board its able to print SHAKE string in UART. the problem is

1).what is meaning of Tap. ineed to tap on MMA7660 or i need to shake the sensor up and down. how to tap the sensor(MMA74660) to get TAP bit in TILT register to set.

2). if i tap the sensor the TAP bit not changing in TILT register.

3. if i want to read the register value i done fallowing. and also wanted to change register value but it is not worked.

    uint8_t reg1[2] = {MMA7660_REG_PDET,TAP_THS};
   
    nrf_drv_twi_tx(&m_twi_mma_7660, MMA7660_ADDR, reg1, sizeof(reg1), false);
   
            ret_code_t err_code;
   
            uint8_t value;
   
            uint8_t addr = MMA7660_REG_TILT;
   
            err_code = nrf_drv_twi_tx(&m_twi_mma_7660, MMA7660_ADDR, &addr, 1, true);
   
            if (NRF_SUCCESS == err_code)
   
                err_code = nrf_drv_twi_rx(&m_twi_mma_7660, MMA7660_ADDR, (uint8_t*)&value, sizeof(value));
   
            APP_ERROR_CHECK(err_code);
   
           // printf("\n\r PDT(0x09) %x",TILT_TAP_MASK);
   
               printf("\n\r MMA7660_REG_TILT(0x03) %d",value);
   

this is not changing the MMA7660_REG_TILT(0x03) register value how i can read it.

Thankyou

[Alex]

I'm not familiar with MMA74660 but after writing to any register how do you know if it was changed or not if before printf you don't read register back from MMA74660? Also looking at datasheet found "NOTE: To write to the registers the MODE bit in the MODE (0x07) register must be set to 0, placing the device in Standby Mode. ".

[Alex]

Did you try to follow this note "NOTE: To write to the registers the MODE bit in the MODE (0x07) register must be set to 0, placing the device in Standby Mode. "?

[saiteja]

yes i tried it. it is giving NRF_SUCCESS return value. but i am unable to read the register value.

[dav lion]

I'm using the MMA7660 in a production board, and gave up trying to get Tap to work. Shake works great, both sampled and as an interrupt source. XYZ values read perfectly. The spec-sheet for the chip notes that Tap is only available when sampling rate is set very high (== higher battery consumption), so you might try that, though I did, without success.

[saiteja]

Hi Thank you for reply, i am using TWI_Sensor example code to get Accelerometer(MMA7660) data it is giving XYZ and shake info. here what can be the sample rate i need to use to get TAP. here i am using NRF_TWI_FREQ_400K.

the first thing is i am unable to read and write on registers in accelerometer(that i already mentioned). once againg thank you very much for responding.