How to view LOG from nRF52840 USB CDC example

[jwcheon]

Hi,
I am working on the project through the USB CDC example.

I know how to view log using RTT Viewer through J-Link and UART-LOG using UART.

But how can I see LOG with only CDC-USB connected?

I am using Putty to connect to the COM port that came with the CDC-USB, and the CDC does not work. If I am running CDC, I can not see the LOG.

I wonder if there is a way to view LOG with only USB-CDC connected except the above two methods.

[Stian Røed Hafskjold]

Unfortunately, there's no built-in functionality to redirect the logging calls to the USB peripheral. However, you can define your own backed for logging. If you look at nrf_log_backend_uart.c you can see how the backend is implemented, so you can use this as a starting point and rewrite it for the USB peripheral.

Or, you can start out with the USB CDC example in the sdk and use app_usbd_cdc_acm_write() to print out your log messages.

[karelv]

I'm looking for exactly the same feature; I would be logical to me to be able to sent the log over the usb CDC serial uart...

jwcheon did you made any progress? Can you share? Thx.

[Saagar]

Hi, can you tell me how to see logs using j-link ..i have connected swdio,swdclk,VCC,gnd  from dongle  to j-link but the dongle is not being detected.. thanks in advance

[Brian Hung]

in my test case , i'm using usb interactive example,i need using CDC ACM port to read log,
so  i change nrf_cli_init parameter from NRF_LOG_SEVERITY_ERROR to NRF_LOG_SEVERITY_INFO and it works for me.

static void cli_init(void) 
{ 
    ret_code_t ret; 
#if CLI_OVER_USB_CDC_ACM 
    //ret = nrf_cli_init(&m_cli_cdc_acm, NULL, true, true, NRF_LOG_SEVERITY_ERROR); 
    ret = nrf_cli_init(&m_cli_cdc_acm, NULL, true, true, NRF_LOG_SEVERITY_INFO); 
    APP_ERROR_CHECK(ret); 
#endif 
#if CLI_OVER_UART 
    nrf_drv_uart_config_t uart_config = NRF_DRV_UART_DEFAULT_CONFIG; 
    uart_config.pseltxd = TX_PIN_NUMBER; 
    uart_config.pselrxd = RX_PIN_NUMBER; 
    #ifdef HWFC uart_config.pselcts = CTS_PIN_NUMBER; 
    uart_config.pselrts = RTS_PIN_NUMBER; 
    uart_config.hwfc = NRF_UART_HWFC_ENABLED; 
    #endif 
    ret = nrf_cli_init(&m_cli_uart, &uart_config, true, true, NRF_LOG_SEVERITY_ERROR); 
    APP_ERROR_CHECK(ret); 
#endif 
}