How to retrieve Value from multiple Characteristics based Service Handler p_ble_evt->header.evt_id.?

[Smit]

Hi,

 I have one service UUID ffe0 that has two characteristics: one of has UUID ffe4 use for "notify" and other one has UUID ffe5 use for "write and read".

Now i want to get the data from the FFE5 and reply accordingly as per the data that I received from FFE5 suppose I write send data from mobile App to board is "SEND=1" as string to characteristic  UUID FFE5 now according to the message received from the FFE5 service i.e. SEND=1 I want to reflect the characteristic UUID FFE4 as "OK" if the string matches as SEND=1. Now My main Question is How i know when the data is being received from FFE5 characteristic UUID. If I get that as an interrupt or anything I will send a reply as "OK" over the characteristic  UUID FFE4.

I have also created NRF_SDH_BLE_OBSERVER for that service.

But how to get value from the different characteristics UUID like 0xFFE5 and so forth if any .

	switch (p_ble_evt->header.evt_id)
        {
            case BLE_GAP_EVT_CONNECTED:
                p_our_service->conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
                break;
            case BLE_GAP_EVT_DISCONNECTED:
                p_our_service->conn_handle = BLE_CONN_HANDLE_INVALID;
                break;
            default:
                // No implementation needed.
                break;
        }
        
        

Thanks in advance.

[Edvin]

Hello,

I suggest that you check out the ble_app_uart example, which works pretty much the way that you describe. There is one characteristic for notifications, and one with write (not read).

Check out how ble_nus.c generates the event BLE_NUS_EVT_RX_DATA from the BLE_GATTS_EVT_WRITE event in ble_nus_on_ble_evt()

ble_nus_on_ble_evt() is assigned through NRF_SDH_BLE_OBSERVER(), probably like you have done.

BR,

Edvin

[Smit]

I have made certain changes in the code that you suggested to go through for the quick checking I bypass the app_uart_put that is sending the received data from  Nordic UART BLE Service to UART and instead according to my application I fetch it for my purpose and got trigger for new data as I just wanted for my application explained above and send that received bytes from nus_data_handler over BLE TX Service as Notification.

As per below code :

static void nus_data_handler(ble_nus_evt_t * p_evt)
{

    static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
    if (p_evt->type == BLE_NUS_EVT_RX_DATA)
    {
        uint32_t err_code;

        NRF_LOG_DEBUG("Received data from BLE NUS. Writing data on UART.");
        NRF_LOG_HEXDUMP_DEBUG(p_evt->params.rx_data.p_data, p_evt->params.rx_data.length);
/* Do Not Send to UART 
        for (uint32_t i = 0; i < p_evt->params.rx_data.length; i++)
        {
            do
            {
                err_code = app_uart_put(p_evt->params.rx_data.p_data[i]);
                if ((err_code != NRF_SUCCESS) && (err_code != NRF_ERROR_BUSY))
                {
                    NRF_LOG_ERROR("Failed receiving NUS message. Error 0x%x. ", err_code);
                    APP_ERROR_CHECK(err_code);
                }
            } while (err_code == NRF_ERROR_BUSY);
        }
        if (p_evt->params.rx_data.p_data[p_evt->params.rx_data.length - 1] == '\r')
        {
            while (app_uart_put('\n') == NRF_ERROR_BUSY);
        }
 */


            do
            {
                uint16_t length = (uint16_t)p_evt->params.rx_data.length;
                memcpy(data_array , p_evt->params.rx_data.p_data, length);
                err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
                if ((err_code != NRF_ERROR_INVALID_STATE) &&
                    (err_code != NRF_ERROR_RESOURCES) &&
                    (err_code != NRF_ERROR_NOT_FOUND))
                {
                    APP_ERROR_CHECK(err_code);
                }
            } while (err_code == NRF_ERROR_RESOURCES);
    }

}

Is this way correct, as such i am half way instead of bridging the same data i want to analysis the received data from the BLE_NUS_EVT_RX_DATA and then after this I will call ble_nus_data_send .


Please check the same so that it will get verified from your end also for future use.

Thanks in advance

[Edvin]

Looks good!

One tiny thing you can look into if you want to power optimize your application (minor detail). 

Your do{} while() loop will make sure that the packet is sent in a proper way. However, if you ever get the NRF_ERROR_RESOURCES return value, you will not allow the chip to go to sleep before it returns NRF_SUCCESS. To further optimize this, you can save the data in some array in your application, leave the event, and then retransmit it on the next BLE_GATTS_EVT_HVN_TX_COMPLETE (you can add this event to your main.c's ble_evt_handler()).

[Smit]

OK Thank you for evaluating it,

I understand your point about the consequences of the do{} while() loop  with NRF_ERROR_RESOURCES,

But i am still not sure how to implement as you explained in as 

Edvin said:

To further optimize this, you can save the data in some array in your application, leave the event, and then retransmit it on the next BLE_GATTS_EVT_HVN_TX_COMPLETE (you can add this event to your main.c's ble_evt_handler()).

Can you please explain as in some code snippet of the same thing i want to do as per your technique!

It would be great help to have !

And also one thing that i explained is the trigger of the RX characteristics is important to me as to know that data is received too.

[Edvin]

volatile bool send_flag = false;
volatile bool more_data = false;
volatile uint8_t data_array[MAX_LENGTH];
volatile uint16_t data_length;


static void ble_evt_handler(...)
{
    ...
    case BLE_GATTS_EVT_HVN_TX_COMPLETE:
        if (more_data)
        {
            send_flag = true;
        }
        break;
}

static void nus_data_handler(ble_nus_evt_t * p_evt)
{
    ...
    if (p_evt->type == BLE_NUS_EVT_RX_DATA)
    {
        // Copy data from event to your custom data_array.
        for (uint8_t i=0; i<p_evt->....len; i++)
        {
            data_array[i] = p_evt->....data[i];
        }
        data_length = p_evt->...len;
        send_flag = true;
        more_data = true;
    }
}


int main(void)
{
    // Init everything.
    
    ...
    for(;;)
    {
        if (send_flag)
        {
            send_flag = false;
            err_code = send_data()
            if (err_code == NRF_SUCCESS)
            {
                
                more_data = false;
            }
        }
        
        idle_state_handle
    }
}

Something like this. Send the data from main, and only try again if the TX_COMPLETE event occurs and you have more data to send.

BR,
Edvin

[Smit]

Ok thank Edvin for really quick help and I got it ,

Just to confirm the send_data() would it be as below?:

uint32_t send_data(void)
{
    return ble_nus_data_send(&m_nus, data_array, &data_length, m_conn_handle);

}

Is above send_data() function enough or more preventive code require as far as other nRF flags are concerned ?

[Smit]

It worked as you told without NRF_ERROR_RESOURCES as per your suggested code snippet and also above send_data function too.

Is any other preventive measure to take care of  for final implementation !!!

Please give suggestion for the same.

Thank you in advance.

[Edvin]

I think you are good, if the application works and does what you want it to do.