printf() with the FRDM-KL25Z Board and without Processor Expert

in this tutorial i explored how to use printf(), and this tutorial is so generic that it works for any processor/microcontroller. that flexibility is because i’m using processor expert. in case processor expert shall not be used, then some tweaks are needed. here i show what is needed to have printf() working with the frdm-kl25z board. i use the uart0 connected to opensda usb cdc for this.

creating the project

i create a new bareboard project. nothing special here, except that ‘uart’ should be selected:

uart set for new project settings

low level uart support

as explained in this tutorial i, i need low-level uart support. codewarrior comes with the needed files for the twr-kl25z in “\mcu\arm_gcc_support\uart\twr-kl25z128″:

low level uart support files

i copy these files into my project:

copied low level uart support files

the twr-kl25z is using uart0 with pta14/pta15, while the frdm-kl25z is using uart0, but pta1/pta2. so i need to change the pin settings.

for this i disable in consoleio.c, in consoleio_init() the settings for the tower board, and add my change to use pta1/pta2:

void consoleio_init()
{
    initclock();
 
    /* sim_scgc4: uart0=1 */
    sim_scgc4 |= sim_scgc4_uart0_mask;
#if 0 /* twr version: pta14, pta15 */
    /* porta_pcr15: isf=0,mux=3 */
    porta_pcr15 = (uint32_t)((porta_pcr15 & (uint32_t)~(uint32_t)(
                 port_pcr_isf_mask |
                 port_pcr_mux(0x04)
                )) | (uint32_t)(
                 port_pcr_mux(0x03)
                ));
    /* porta_pcr14: isf=0,mux=3 */
    porta_pcr14 = (uint32_t)((porta_pcr14 & (uint32_t)~(uint32_t)(
                 port_pcr_isf_mask |
                 port_pcr_mux(0x04)
                )) | (uint32_t)(
                 port_pcr_mux(0x03)
                ));
#else /* frdm-kl25z: pta1/pta2 */
      /* porta_pcr1: isf=0,mux=2 */
      porta_pcr1 = (uint32_t)((porta_pcr1 & (uint32_t)~0x01000500ul) | (uint32_t)0x0200ul);
      /* porta_pcr2: isf=0,mux=2 */
      porta_pcr2 = (uint32_t)((porta_pcr2 & (uint32_t)~0x01000500ul) | (uint32_t)0x0200ul);
#endif
    uart0_pdd_enabletransmitter(uart0_base_ptr, pdd_disable); /* disable transmitter. */
    uart0_pdd_enablereceiver(uart0_base_ptr, pdd_disable); /* disable receiver. */
    /* uart0_c1: loops=0,dozeen=0,rsrc=0,m=0,wake=0,ilt=0,pe=0,pt=0 */
    uart0_c1 = 0x00u;                    /*  set the c1 register */
    /* uart0_c3: r8t9=0,r9t8=0,txdir=0,txinv=0,orie=0,neie=0,feie=0,peie=0 */
    uart0_c3 = 0x00u;                    /*  set the c3 register */
    /* uart0_s2: lbkdif=0,rxedgif=0,msbf=0,rxinv=0,rwuid=0,brk13=0,lbkde=0,raf=0 */
    uart0_s2 = 0x00u;                    /*  set the s2 register */
    uart0_pdd_setclocksource(uart0_base_ptr, uart0_pdd_pll_fll_clock);
    uart0_pdd_setbaudrate(uart0_base_ptr, 313u); /* set the baud rate register. */
    uart0_pdd_setoversamplingratio(uart0_base_ptr, 3u);
    uart0_pdd_enablesamplingonbothedges(uart0_base_ptr, pdd_enable);
    uart0_pdd_enabletransmitter(uart0_base_ptr, pdd_enable); /* enable transmitter */
    uart0_pdd_enablereceiver(uart0_base_ptr, pdd_enable); /* enable receiver */
}

to use different uart/port settings, the easiest way is to use a processor expert project as explained in this tutorial .

example code

for testing, i print a ‘hello world’ from the main() in main.c:

/*
 * main implementation: use this 'c' sample to create your own application
 *
 */
 
#include "derivative.h" /* include peripheral declarations */
#include
#include "consoleio.h"
 
int main(void)
{
    int counter = 0;
 
    consoleio_init();
    for(;;) {
        counter++;
        printf("hello world!\r\n");
    }
    return 0;
}

do not forget to include the correct header files, and to call consoleio_init()!

that’s it! build, download and hopefully you see the messages printed to the console .

project on github

for reference, i have committed the codewarrior project and sources on github here .

happy printing