UART doesn't work well with GCC

RE: UART doesn't work well with GCC

Roger Clark — Wed, 08 Mar 2017 21:01:34 GMT

NRF_LOG works fine on custom boards, you just need to set the Tx and Rx pin numbers in sdk_config.h

PS. Please post your solution in case its more flexible than usimg NRF_LOG

RE: UART doesn't work well with GCC

manymany — Wed, 08 Mar 2017 15:04:26 GMT

I use a custom board without J-Link so I think NRF_LOG couldn't work in that case.

For now as a workaround solution I created a custom printf including app_uart_put() which is working fine. But if somebody is able to use printf with GCC i'm interested to know how to to that. It seem that it is a very common feature, I don't understand why nobody can give me a clear answer !

As retarget.c contains #elif defined(GNUC) means that it is not only for Keil ?

RE: UART doesn't work well with GCC

bjorn-spockeli — Wed, 08 Mar 2017 13:18:02 GMT

Again, the retarget.c file is Keil specific. I suggest that you use NRF_LOG_INFO instead as this works with both Keil and GCC.

RE: UART doesn't work well with GCC

manymany — Wed, 08 Mar 2017 11:36:01 GMT

printf seems to use _write from retarget.c

int _write(int file, const char * p_char, int len)
{
    int i;

    UNUSED_PARAMETER(file);

    for (i = 0; i < len; i++)
    {
        UNUSED_VARIABLE(app_uart_put(*p_char++));
    }

    return len;
}

But nothing explain that it prints only lines (with \n).

If I use app_uart_put() it print directly without waiting a "\n"

RE: UART doesn't work well with GCC

bjorn-spockeli — Wed, 08 Mar 2017 09:52:05 GMT

In the Keil projects we have included retarget.c, which retargets printf() to app_uart_put(). Note that retarget is Keil specific, so you will have to do the same for GCC. Alternativly you can use the NRF_LOG macros as suggested by @rogerclark

RE: UART doesn't work well with GCC

Roger Clark — Wed, 08 Mar 2017 06:37:20 GMT

Not sure about printf, but using NRF_LOG commands I sometimes have to "flush" to see the data.