Zhiyong Li

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

10 years, 9 months ago.

NTPClient::setTime returns NTP_OK even when ethernet cable is unplugged?

I was trying to use NTPClient::setTime as a way to check whether internet access is available, somehow it doesn't work. As stated in the tittle, even when Ethernet cable is unplugged, setTime returns 0(NTP_OK).

This seems rather wired. Did this happen to anyone of you?

Thanks, ZL

Question relating to:

Last updated: 05 Aug 2012

1 Answer

David Smart
10 years, 9 months ago.

Hi ZL,

Donatien's sample is simplified, to focus the reader only on the NTP client functions. For a more detailed, and robust solution, the program needs to check the return values from the prior function calls.

This is extracted from one of my applications (and then I modified it for the NTP example). 

RawSerial pc(USBTX, USBRX);
EthernetInterface eth;

// This function returns the current status of connection.
bool get_link_status(void)
{
    uint32_t tmp = lpc_mii_read_data();
    return (tmp & DP8_VALID_LINK) ? true : false;
}


...
    pc.printf("Initializing network interface...\r\n");
    if (0 == eth.init()) {
        // It should always take this path
        do {
            pc.printf("Connecting to network...\r\n");
            if (0 == eth.connect()) {
                pc.printf("Ethernet connected as %s\r\n", eth.getIPAddress());
                while (get_link_status()) {
                    //pc.printf("Connection is good.\r\n");
                    if (pc.readable()) {
                        int c = pc.getc();
                        switch (c) {
                            case 'r':
                                mbed_reset();
                                break;
                            case 't':
                                if (ntp.setTime("0.pool.ntp.org") == 0) {
                                    printf("Set time successfully\r\n");
                                }
                                break;
                            default:
                                pc.printf("Menu:\r\n"
                                    "  t - Time set from NTP server.\r\n"
                                    "  r - reset\r\n"
                                    );
                                break;
                        } // switch
                    }  // if pc.readable()
                }  // while (get_link_status())
                pc.printf("lost connection.\r\n");
                eth.disconnect();
            } else {
                pc.printf("  ... failed to connect.\r\n");
            }
        } while (1);
    } else {
        pc.printf("  ... failed to initialize, rebooting...\r\n");
        mbed_reset();
    }

Accepted Answer