nRF52840 USBD_BLE_UART for central device

[juulee]

Hi all, I'm developing nRF52840-DK to use it as an central device.

Base example is usbd_ble_uart: I'm going to communicate with peripheral device using BLE, and control central device by connect it to PC. (Also central device send data to PC)

Diagram: Peripheral <---> Central <---> PC

                                   BLE               USB

So I modified code, and check that my command from PC went through Central device and central sent data to peripheral device, successfully.

However, I have problem on opposite part: receiving data from central to PC.

When I turn on PUTTY, received data are shown like this. I don't know how to fix it.

Data format from peripheral device to central: uint8_t array, with size of 243: Peripheral is nrf52832, and it sends ADC data.

I checked that peripheral device works well (checked through nrf connect app)

And here's my code related to BLE receiving part (central device)

static void ble_nus_c_evt_handler(ble_nus_c_t * p_ble_nus_c, ble_nus_c_evt_t const * p_ble_nus_evt) //check
{
    ret_code_t err_code;

    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.");
            NRF_LOG_RAW_INFO("Connected to device.\r\n");
            break;

        case BLE_NUS_C_EVT_NUS_TX_EVT:
            //NRF_LOG_INFO("Received data\r\n");
            nus_data_handler(p_ble_nus_evt->p_data, p_ble_nus_evt->data_len);
            break;

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


static void nus_data_handler(uint8_t * p_data, uint16_t data_len) //check
{
        bsp_board_led_invert(LED_BLE_NUS_RX);
        NRF_LOG_RAW_INFO("Received data from BLE NUS. Writing data on CDC ACM.\r\n");
        NRF_LOG_HEXDUMP_DEBUG(p_data, data_len);
        memcpy(m_nus_data_array, p_data, data_len);

        // Add endline characters
        uint16_t length = data_len;
        if (length + sizeof(ENDLINE_STRING) < BLE_NUS_MAX_DATA_LEN)
        {
            memcpy(m_nus_data_array + length, ENDLINE_STRING, sizeof(ENDLINE_STRING));
            length += sizeof(ENDLINE_STRING);
        }

        // Send data through CDC ACM
        ret_code_t ret = app_usbd_cdc_acm_write(&m_app_cdc_acm,
                                                m_nus_data_array,
                                                length);
        if(ret != NRF_SUCCESS)
        {
            NRF_LOG_RAW_INFO("CDC ACM unavailable, data received: %s\r\n", m_nus_data_array);
        }    
}

I used codes of ble_app_uart example also, so function  names are related to NUS haha.

Thanks for looking this.

I wish I can get nice advice.

[Susheel Nuguru]

sorry for late reply Juulee,

Just back from easter holidays here in Norway. I will take a look at your case tomorrow. Thanks for understanding.

[Susheel Nuguru]

I do not see anything wrong in your data handling on the central side. The snapshot of putty seems to be the difference in baudrate in which you opened putty and the baudrate with which the nRF52 is operating. Make sure that your PUTTY configuration are similar to the setting you used for UART peripheral in the nRF52 to which the PUTTY is connected to.

[juulee]

Ah, I'm using usbd, not UART. So baudrate doesn't matter..

In my opinion, this happens because of data format.

From the original example, I remember that nRF52840 receives data array in char format.

But here, I changed it to uint8_t, because my peripheral device sends the data in that form.

So while doing memcpy from uint8_t to char m_nus_data_array, computer cannot understand the data I think, maybe in the process of ASCII? I don't know...

What do you think? Do you have any idea or suggestions?

Thanks for reply.

[Susheel Nuguru]

looking at your terminal output, it seems that one character is logged a lot of times, so I would assume that this is not a formatting issue. In anycase, you can try to change your uint8_t back to char and see if you see any difference.