BLE UART connection status

RE: BLE UART connection status

awneil — Tue, 11 Jun 2019 15:23:05 GMT

[quote userid="6462" url="~/f/nordic-q-a/48031/ble-uart-connection-status/192139"]Sometimes (too often?), Nordic's idea of "descriptive" does seem rather lacking[/quote]

In this case, the description of BLE_ADV_EVT_IDLE is just plain wrong:

BLE_ADV_EVT_IDLE,                /**< Idle; no connectable advertising is ongoing.*/

That's not a description of the Event - that's a description of the State which is entered after the event has occurred!

EDIT

The fact that the "Indefinite" option is not referenced from any of the places where you might use it has already been noted:

https://devzone.nordicsemi.com/f/nordic-q-a/46515/fast-advertising-slow-advertising-and-indefinite-advertising/183141#183141

maybe they'll find someone soon ...

;)

RE: BLE UART connection status

awneil — Tue, 11 Jun 2019 15:19:31 GMT

[quote userid="74971" url="~/f/nordic-q-a/48031/ble-uart-connection-status/192134"]Where is this stuff documented[/quote]

Here:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.3.0/lib_ble_advertising.html

You can also use your IDE's 'Go To Definition' feature to find the definition of BLE_ADV_EVT_IDLE - where there should be a descriptive comment:

/**@brief   Advertising events.
 *
 * @details These events are propagated to the main application if a handler was provided during
 *          initialization of the Advertising Module. Events for modes that are not used can be
 *          ignored. Similarly, BLE_ADV_EVT_WHITELIST_REQUEST and BLE_ADV_EVT_PEER_ADDR_REQUEST
 *          can be ignored if whitelist and direct advertising is not used.
 */
typedef enum
{
    BLE_ADV_EVT_IDLE,                /**< Idle; no connectable advertising is ongoing.*/
    BLE_ADV_EVT_DIRECTED_HIGH_DUTY,  /**< Direct advertising mode has started. */
    BLE_ADV_EVT_DIRECTED,            /**< Directed advertising (low duty cycle) has started. */
    BLE_ADV_EVT_FAST,                /**< Fast advertising mode has started. */
    BLE_ADV_EVT_SLOW,                /**< Slow advertising mode has started. */
    BLE_ADV_EVT_FAST_WHITELIST,      /**< Fast advertising mode using the whitelist has started. */
    BLE_ADV_EVT_SLOW_WHITELIST,      /**< Slow advertising mode using the whitelist has started. */
    BLE_ADV_EVT_WHITELIST_REQUEST,   /**< Request a whitelist from the main application. For whitelist advertising to work, the whitelist must be set when this event occurs. */
    BLE_ADV_EVT_PEER_ADDR_REQUEST    /**< Request a peer address from the main application. For directed advertising to work, the peer address must be set when this event occurs. */
} ble_adv_evt_t;

Sometimes (too often?), Nordic's idea of "descriptive" does seem rather lacking

😞

Also, where to find the documentation is not always obvious: it'll be in the InfoCenter somewhere - but finding it is not always so easy ...

RE: BLE UART connection status

Robin — Tue, 11 Jun 2019 15:08:30 GMT

Mr. Neil,

Should I presume that BLE_ADV_EVT_IDLE is the flag for the timeout? Where is this stuff documented?

RE: BLE UART connection status

awneil — Tue, 11 Jun 2019 09:01:34 GMT

[quote userid="74971" url="~/f/nordic-q-a/48031/ble-uart-connection-status/191903"]the advertising module puts the processor to sleep after a 3 minute timeout,[/quote]

It's not actually the Advertising Module itself which does it; it's "your" app - when it receives the Timeout event from the Advertising Module.

Two options:

Set the advertising to never time out - use BLE_GAP_ADV_TIMEOUT_GENERAL_UNLIMITED;
Just re-start advertising on each timeout
There'l be an "advertising start" function called somewhere early on - just call that again.

[quote userid="74971" url="~/f/nordic-q-a/48031/ble-uart-connection-status/191903"]I have commented out the line that puts the cpu to sleep, and the code keeps running, but I cannot reconnect after the timeout. [/quote]

Indeed - with no advertising, your device cannot be seen and, therefore, you can't connect to it.

RE: BLE UART connection status

Robin — Tue, 11 Jun 2019 03:52:02 GMT

Hello again Simon,

Well I believe I have tracked this down to the fact that the advertising module puts the processor to sleep after a 3 minute timeout, presumably APP_ADV_TIMEOUT_IN_SECONDS (180). I can't see through the advertising module documentation well enough to understand how to properly and selectively, based on the state of our application, ignore the BLE_ADV_EVT_IDLE flag. I have commented out the line that puts the cpu to sleep, and the code keeps running, but I cannot reconnect after the timeout.

static void on_adv_evt(ble_adv_evt_t ble_adv_evt)
{
    uint32_t err_code;

    switch (ble_adv_evt)
    {
        case BLE_ADV_EVT_FAST:
            err_code = bsp_indication_set(BSP_INDICATE_ADVERTISING);
            APP_ERROR_CHECK(err_code);
            break;
        case BLE_ADV_EVT_IDLE:
 //           sleep_mode_enter();
            break;
        default:
            break;
    }
}

Any help is greatly appreciated,

Robin@TL

RE: BLE UART connection status

Robin — Mon, 10 Jun 2019 22:50:14 GMT

Another note that might help, is that our board does not have a hardware uart peripheral. All i/o is via the ble uart interface.

RE: BLE UART connection status

Robin — Mon, 10 Jun 2019 19:24:41 GMT

Hello,

I have no need to save the data for later transmission so I bypass the ble_nus_string_send() if disconnected.

Which specific example are you referring to, please?

Thanks

Robin

RE: BLE UART connection status

awneil — Mon, 10 Jun 2019 19:09:23 GMT

[quote userid="74971" url="~/f/nordic-q-a/48031/ble-uart-connection-status/191884"]I think my code sends nothing if not connected[/quote]

But, in that case, you are saving up the data to be sent when you are next connected - yes?

So, the longer you are disconnected, the more data is going to be waiting to be sent when it reconnects.

The logic of your loop is not correct: you keep calling ble_nus_string_send() within the loop without checking its return while the call in the control clause returns other than success!

Take a look at how Nordic do it in the example ...

RE: BLE UART connection status

Robin — Mon, 10 Jun 2019 18:59:30 GMT

Hello awneil,

I think my code sends nothing if not connected. There is a if (connected) qualifier in the loop. Since the last post I did add a while loop looking for a NRF_SUCCESS, but it did not help. Am I missing something else here?

static void send_str(const char * str)
{
  if (connected)  // This should preclude any sending if disconnected..
  {
    uint8_t i = 0;
    while ((str[i] != 0x0A) && (str[i] != 0x00) && (i < BLE_NUS_MAX_DATA_LEN)) 
    {
      i+=1;
    }
    if (str[i] == 0x00)
      i-=1;   
    // wait until errors clear...
    while (ble_nus_string_send(&m_nus, (uint8_t*)str, i+1) != NRF_SUCCESS)
      ble_nus_string_send(&m_nus, (uint8_t*)str, i+1);
  }
}

RE: BLE UART connection status

awneil — Mon, 10 Jun 2019 18:26:03 GMT

If you've been disconnected for a "long" time, there will be a "lot" of waiting data to be sent

Your posted code doesn't check the return code from ble_nus_string_send() - it just keeps flinging data at it.

At some point, it is going to get overwhelmed - that point is, presumably, your "couple of minutes".

The error code NRF_ERROR_RESOURCES indicates that it is "full" - so you need to hold-off sending for a while...

RE: BLE UART connection status

Robin — Mon, 10 Jun 2019 18:02:03 GMT

Hello again Simon,

I was premature in my assessment below that I had this working. It only holds up for a couple minutes after the central disconnects. If continually connect/disconnect, all seems fine, but if it stays disconnected for any length of time the peripheral crashes and needs to be powered down to restart correctly.

To attempt to clarify what we are attempting, please consider the following rewording of the problem:

We are using a Nordic USB dongle as a ble_uart_central to communicate commands and responses over bluetooth between our board (which is based on the ble_uart_peripheral) and a host computer/terminal emulator. Our board has code for performing long time duration (up to 24 hours) stabilization testing. During this test, status updates are sent back to the host every 10 seconds or so. The test must remain in effect if the central disconnect for any reason, with the intention of reconnecting later to resume and interpret the messaging. So, the code snippet below shows how we understood this could be done, from our reading of similar posts. However, as mentioned, it only holds up for a couple minutes of disconnect time and then the board crashes. So long as we stay connected, the code runs to completion.

Anything you can offer on how this might be resolved is greatly appreciated.

Thank you in advance,

Robin@TL

RE: BLE UART connection status

Robin — Sat, 01 Jun 2019 05:56:48 GMT

Here are snippets of what I did, in case anyone is interested.

// Inside Main
//...

static bool connected = false;

//...

// Inside send_string()...

static void send_str(const char * str)
{
  if (connected)
  {
    uint8_t i = 0;
    while ((str[i] != 0x0A) && (str[i] != 0x00) && (i < BLE_NUS_MAX_DATA_LEN)) 
    {
      i+=1;
    }
    if (str[i] == 0x00)
      i-=1;
    ble_nus_string_send(&m_nus, (uint8_t*)str, i+1);
  }
}

// Inside on_ble_evt...

    case BLE_GAP_EVT_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;
      connected = true;
    break;
    case BLE_GAP_EVT_DISCONNECTED:
      err_code = bsp_indication_set(BSP_INDICATE_IDLE);
      APP_ERROR_CHECK(err_code);
      m_conn_handle = BLE_CONN_HANDLE_INVALID;
      connected = false;
//...

RE: BLE UART connection status

Robin — Sat, 01 Jun 2019 05:49:54 GMT

Hello all,

I have this finally figured out. Thanks to everyone for their help ans support.

Robin@TL

RE: BLE UART connection status

awneil — Fri, 31 May 2019 14:21:44 GMT

You can look at the Connection Handle:

if its value is BLE_CONN_HANDLE_INVALID, then you are not connected;
otherwise, you are.

It changes state on the BLE_GAP_EVT_DISCONNECTED and BLE_GAP_EVT_CONNECTED events.

RE: BLE UART connection status

Robin — Fri, 31 May 2019 14:13:51 GMT

Hello Simon,

The LED is not an option. This need to happen without operator intervention, so yes, a return variable would work, but the process needs to be "synchronized" with the nus send string function. And thank you for noting this case is not public. I thought I had checked that option.

Robin

RE: BLE UART connection status

Simonr — Fri, 31 May 2019 10:10:08 GMT

Hi Robin

I'm having some trouble understanding what exactly you want. Do you mean like a return value when the peripheral connects/disconnects to a central? Because this can be seen if connecting it to a terminal or something similar. You should also be able to implement an LED to turn on when connected and off when disconnected if that is what you are after.

If I have misunderstood what you want to achieve, please try to explain it again.

NOTE: Creating a public case would let the community come with suggestions as well, which increases the chance of someone providing I.E. a working example of what you want. We can also set this case to public mode if you'd like. Just give me the word.

Best regards,

Simon