Connection problems with Android 7 and SDK12.1

[janR]

We have problems when connecting to a device running softdevice S132 version 3.0 with a tablet running Android 7.0.

When we use tablet and nRF Connect, we get Error 8 (0x8): GATT CONN TIMEOUT and Error 133 (0x85): GATT ERROR and disconnect. Softdevice asserts with id = 1 and pc = 0x0001A216 when we try to connect.

With Android 6.0 there is no problem.

Tablet is a Samsung SM-T580 running Android 7.0

Problem is reproducable with ble_app_hrs_freertos example project from SDK12.1

Is this a known problem, and is there any way around it?

Regards, Jan

[Sigurd]

Hi,

This is a known issue with the SM-T580. It could be that when you upgraded to Android 7.0, long MTU or DLE support was added. These Samsung Tab A tablets are known for breaking the BLE spec by sending version exchange and length request in parallel (i.e., does not wait for the peripheral to respond before sending the next control packet). Since you are using SDK12 and nRF52, I suggest that you upgrade to S132 V3.1.0 and enable compatibility mode 2. This mode enables interoperability with these types of devices. You should also disable DLE via the options API.

Upgrade to 132 v.3.1.0:

When you download S132 V3.0.1 from here. You should replace the header files in the SDK(located in the folder SDK_folder\components\softdevice\s132\headers\) with the ones you download(located in folder s132_nrf52_3.1.0\s132_nrf52_3.1.0_API\include)

Enable compatibility mode 2:

ble_opt_t ble_opt;
memset(&ble_opt, 0, sizeof(ble_opt));

ble_opt.gap_opt.compat_mode_2.mode_2_enable = 1;

err_code = sd_ble_opt_set(BLE_GAP_OPT_COMPAT_MODE_2,&ble_opt); 
APP_ERROR_CHECK(err_code);

You need to call this after you have enabled the SoftDevice. I.e after softdevice_enable() in ble_stack_init().

Disable DLE via the options API:

Call this function after you have enabled the SoftDevice:

void data_len_ext_set(void)
{
    ret_code_t err_code;
    ble_opt_t  opt;

    memset(&opt, 0x00, sizeof(opt));

    opt.gap_opt.ext_len.rxtx_max_pdu_payload_size = 0;

    err_code = sd_ble_opt_set(BLE_GAP_OPT_EXT_LEN, &opt);
    APP_ERROR_CHECK(err_code);
}

[Sigurd]

Could you test with ble_app_hrs with S132 3.1.0 and the above changes ?