Device connects then disconnects immediately

[apdobaj]

This behavior only occurs when connecting to the phone using the native connection procedure, it does not disconnect when using the nRF Connect app on the phone (Android Pixel 3a). Wireshark and the packet sniffer didn't shed much light, I've played with the connection interval settings, slave latency, update count etc. when I play with the max connection interval and the MTU settings I get a hardware fault.

[Hung Bui]

Please capture and send us a sniffer trace. 

Also please check the disconnect reason when you receive the BLE_GAP_EVT_DISCONNECTED event

[apdobaj]

the code never reaches that case in the ble_evt_handler

static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
    ret_code_t err_code;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected");
            err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
            APP_ERROR_CHECK(err_code);
            m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
            err_code = nrf_ble_qwr_conn_handle_assign(&m_qwr, m_conn_handle);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected");
            
            // Dequeue all keys without transmission.
            (void) buffer_dequeue(false);

            m_conn_handle = BLE_CONN_HANDLE_INVALID;

[Hung Bui]

There must be something wrong that crashed the code make it not reached the BLE_GAP_EVT_DISCONNECTED. 
Please follow this debugging tip: https://devzone.nordicsemi.com/question/60125/my-device-is-freezing-and-restarting/#60126

And please capture a sniffer trace. 

[apdobaj]

Defining DEBUG in the preprocessor doesn't do anything, are there other flags I need to set? Here is the sniffer trace, device is "gestr2"

Wireshark_gestr2.txt

[apdobaj]

Here's another one taken with nRF Connect that connects but then disconnects when reading the characteristics.Wireshark_gestr2.pcapng

[Hung Bui]

What I can see from the trace is that the device crashed after the phone starting the bonding process. Especially when it start exchanging the Identity Address Information. 
I suspect that the application wasn't prepared for storing the identity information. It crashed, either in the stack or in the application. 

The reason it didn't crash when using nRF Connect app is that the app doesn't do bonding automatically when the Bluetooth native connection would do bonding automatically. 

We would need more debug information. Do you see the same issue when testing with the bluetooth example in NCS ? 

[apdobaj]

Yes, the same issue with the HIDS keyboard example that has been modified to fit in the nrf52811 device with 192K of flash and the s112 SD. check out the sdk_config.h to see what's been disabled.5543.sdk_config.h