TWI Scanner Example No device was found 16-bit sensor

[StevenW807]

I'm trying the given example <twi_sensor>.  I connect nRF52 DK P0.26 to my sensor's SDA, nRF52 DK P0.27 connects to my sensor's SCL. My sensor runs at 400kHz, so I modified frequency as NRF_DRV_TWI_FREQ_400K, 16-bit. My PuTTY shows that: 

TWI scanner started.

No device was found.

Sensor I2C sequence is given below. I suspect the reason for having no detection is because of the sensor data is 16-bit? Thanks

[hmolesworth]

One thing to check: The required SDA and SCL 4k7 pull-ups are only enabled via the SHIELD_DETECT signal when a shield is plugged in, otherwise you need to have external pull-ups. If the sensor is hardwired instead of being on a shield board this could be the cause.

[StevenW807]

Thanks! Which pin should I use for the SHIELD_DETECT signal? Is there any link which I could refer to, pls?

[StevenW807]

Here is my code, I guess it's the 16 bit data issue. Plz help if you know how to modify the code. Thanks 

int main(void)
{
    ret_code_t err_code;
    uint8_t address;
    uint8_t sample_data[1]; // 16 bit data, so use "[1]" here
    bool detected_device = false;

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("TWI scanner started.");
    NRF_LOG_FLUSH();
    twi_init();

    for (address = 1; address <= TWI_ADDRESSES; address++)
    {
        err_code = nrf_drv_twi_rx(&m_twi, address, &sample_data, sizeof(sample_data));
        if (err_code == NRF_SUCCESS)
        {
            detected_device = true;
            NRF_LOG_INFO("TWI device detected at address 0x%x.", address);
        }
        NRF_LOG_FLUSH();
    }

    if (!detected_device)
    {
        NRF_LOG_INFO("No device was found.");
        NRF_LOG_FLUSH();
    }

    while (true)
    {
        /* Empty loop. */
    }
}

[hmolesworth]

To use the on-board 4k7 pull-ups for both SDA and SCK SHIELD_DETECT should be low; if not using a plug-in card simply put a jumper between P5 pin 6 and any GND pin.

This is a datasheet for the switch FSA2466-D.PDF used on the DK

[StevenW807]

Thanks! You are right! It works now. 

For reference, check nRF52 DK datasheet P18-19. Cheers