Sending string data over NUS

[Catytu]

Hello,

I am trying to modify the ble_app_uart code so that my peripheral can send data automatically to the central, which in turn can print it on a computer through UART. What I mean is that instead of the ble_nus_string_send() command being called when I press enter, I want the peripheral to send a number automatically from the main.

This is the code I'm using for sending the number in the peripheral, which prints the value of number correct starting at 1:

    uint8_t number = 0;
    uint8_t data[20]; 

    for (;;)
    {

        number = number + 1;

        sprintf((char *)data, "%d", number); 

        ble_nus_string_send(&m_nus, data, sizeof(data));
    }

This is the code in the central, in the case that BLE_NUS_C_EVT_NUS_TX_EVT happens it calls this function:

static void ble_nus_chars_received_uart_print(uint8_t * p_data, uint16_t data_len)
{
    ret_code_t ret_val;

    NRF_LOG_DEBUG("Receiving data.");
    NRF_LOG_HEXDUMP_DEBUG(p_data, data_len);

    for (uint32_t i = 0; i < data_len; i++)
    {
        do
        {
            ret_val = app_uart_put(p_data[i]);
            if ((ret_val != NRF_SUCCESS) && (ret_val != NRF_ERROR_BUSY))
            {
                NRF_LOG_ERROR("app_uart_put failed for index 0x%04x.", i);
                APP_ERROR_CHECK(ret_val);
            }
        } while (ret_val == NRF_ERROR_BUSY);
    }
    if (p_data[data_len-1] == '\r')
    {
        while (app_uart_put('\n') == NRF_ERROR_BUSY);
    }
}

As far as I know, with the ble_nus_string_send the central should receive and print the number on the other PC. From what I know, the central enters ble_nus_c_evt_handler to establish connection but the NUS_TX_EVT is not being called.

How can I fix this? Or is there a better way to send a number from the peripheral and have the central simply print it to UART?

I'm using NRF52832 and S132.

[Catytu]

Data packets are indeed being received by nrf connect. I can see them when I click notify.

The boards automatically connect when I turn on the peripheral and stay connected. I increased the MTU in both to 100. Baudrate in both is 57600.

I am using the examples/ble_central/ble_app_uart_c.

When they connect it is turning on the tx_notifs, it prints "connected" and "disconnected" no problem but "data recieved" is never printed and no data is being printed either. Here is my ble_nus_c_evt_handler in case it helps:

switch (p_ble_nus_evt->evt_type)
    {
        case BLE_NUS_C_EVT_DISCOVERY_COMPLETE:
            NRF_LOG_INFO("Discovery complete.");
            err_code = ble_nus_c_handles_assign(p_ble_nus_c, p_ble_nus_evt->conn_handle, &p_ble_nus_evt->handles);
            APP_ERROR_CHECK(err_code);

            err_code = ble_nus_c_tx_notif_enable(p_ble_nus_c);
            APP_ERROR_CHECK(err_code);
            NRF_LOG_INFO("Connected to device with Nordic UART Service.");
            printf("Connected\r\n");
            break;

        case BLE_NUS_C_EVT_NUS_TX_EVT:
            printf("Data received\r\n");
            ble_nus_chars_received_uart_print(p_ble_nus_evt->p_data, p_ble_nus_evt->data_len);
            break;

        case BLE_NUS_C_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected.");
            printf("Disconnected\r\n");
            scan_start();
            break;
    }

[howard n2wx]

I'm stumped and would need your code to figure out what's wrong, and that's not appropriate (we hardly know each other! :-) 

Hopefully others with better ideas than I have will chime in. FWIW it sounds like you're very close. Final tips would be to make sure there's nothing untoward in the peripheral side's logs (but you have good results with nrf connect......)  

[Catytu]

Thank you kindly for all your help!

[Catytu]

I fixed it! To be honest I'm not sure what I did to make it work.

I just have one more question regarding this: when I try to change the default GATT MTU length higher than 64 bytes the boards stop working completely. Does this mean my boards don't support large MTU negotiation?

[howard n2wx]

Catytu said:

I fixed it! To be honest I'm not sure what I did to make it work.

Congratulations! I knew you were close

Catytu said:

just have one more question regarding this: when I try to change the default GATT MTU length higher than 64 bytes the boards stop working completely. Does this mean my boards don't support large MTU negotiation?

No, it doesn't mean that, your 52832s and s132 v6.x (maybe older ones too) absolutely support large MTU negotiation and it works perfectly.  Did you change NRF_SDH_BLE_GATT_MAX_MTU_SIZE in sdk_config.h?