nRF5340 - peripheral disconnection because out of range

[Gabriele]

Hi,
I'm working on nRF5340 Bluetooth LE peripheral (building environment: NCS 2.6.1, Zephyr 3.5.99).
The net core is populated with the Zephyr HCI RPMsg sample LE Controller as it is.
I experience a disconnection from peer with reason BT_HCI_ERR_CONN_TIMEOUT.
This occurs because the peer is moved out of range.

How to get the application notified in advance of this disconnection event ? 

[Simonr]

Hi

You should be able to get a warning of the connection status by implementing the QoS reports in your application, Please check out the Quality of Service library in NCS available here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/libraries/others/qos.html#quality-of-service. You should be able to make the application put out a warning if the quality goes below a set threshold.

Best regards,

Simon

[Gabriele]

Hi,
this way seems a bit overkilling.
My goal is to ensure the BLE data transmission from peripheral to central restarts seamlessly upon reconnection.
The data transmit function I use is defined in module cp.c like this

int bt_cp_send(struct bt_conn *conn, uint8_t *data, uint16_t len)
{
  int ret;
  struct bt_gatt_notify_params params = {0};
  const struct bt_gatt_attr *attr = &css_svc.attrs[7];

  params.attr = attr;
  params.data = data;
  params.len = len;
  params.func = on_sent_cp;

  if (!conn) {
    ret = bt_gatt_notify_cb(NULL, &params);
  } else if (bt_gatt_is_subscribed(conn, attr, BT_GATT_CCC_NOTIFY)) {
    ret = bt_gatt_notify_cb(conn, &params);
  } else {
    return -EINVAL;
  }

  return ret;
}

Right after a disconnection event due to out of range condition, the function returns -128.
I get on the console

[00:01:22.337,493] <inf> bas: BAS Notifications disabled
[00:01:22.343,231] <inf> cp: BT CP notify is DISABLED
[00:01:22.349,578] <wrn> ble: disconnected from peer 00:E0:4C:32:98:9B (public) [reason: 0x08]
[00[00:01:22.373,229] <err> ble: advertising failed to start [-12]
:01:22.371,948] <wrn> bt_att: Not connected
[00:01:22.387,847] <err> cp: BT CP failed to send data [-128]

At 4th line something gets broken, preventing the advertising to restart clean.
I need to restart advertising to allow a reconnection when the peers get back in range.
Is there a specific action to take upon disconnection in order to avoid this situation ?