Connection to Android isn't stable

[Jeremy Hubbard]

I'm having an issue with maintaining a stable connection with the master control panel on an android device. Using the PCA10000 I am able to get a stable connection with a computer and transmit data, but when I move to an android device it isn't stable.

I started with the example project "nrf51-ble-app-lbs-throughput-test-5.1.0" and instead of continuously transmitting on a button event, I added a timer which triggers every 30ms to transmit 9 bytes acquired from an I2C sensor. It continues to do this until the button is pressed again.

On the android device I can connect to it, but as soon as I press the button to start sending data the connection is lost and the error returned from the transmit function, ble_lbs_data_send(), is 0x3401.

I am using the nRF51822 development kit with the SoftDevice s110, Keilv5 evaluation version. I have also stopped the sensors from measuring and am transmitting dummy data, which doesn't change the error at all.

Thanks, Jeremy

[Jeremy Hubbard]

I have already updated the TWI driver to be softdevice compatible and I can transmit to a computer just fine. I'm not seeing hard faults.

Based on the 0x3401 error thread, I modified the error checking after the ble_lbs_data_send() command to:

err_code = ble_lbs_data_send(&m_lbs, data);
if (err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING 
        && err_code != NRF_SUCCESS 
        && err_code != BLE_ERROR_INVALID_CONN_HANDLE 
        && err_code != NRF_ERROR_INVALID_STATE 
        && err_code != BLE_ERROR_NO_TX_BUFFERS)
{
    APP_ERROR_CHECK(err_code);
}

and now I can transmit data, but after the connection is established with the Android device it disconnects every 16.5 seconds, like clockwork. Any ideas?

Thanks, Jeremy

[Ole Morten]

Have you tried using the sniffer to see what happens on-air? https://www.nordicsemi.com/eng/content/download/39099/660783/file/ble-sniffer_win_0.9.5.zip

Also, what is the reason when you get the DISCONNECTED event on the nRF51 side? You should also check that it isn't a connection parameter update that's failing, i.e. that you're asking for parameters that the Android device doesn't accept. If so, you'll see on_conn_params_evt() being called with evt_type BLE_CONN_PARAMS_EVT_FAILED. Do you see this when running with a debugger?