Kinetis MicrocontrollersのトピックControlling a RGB led with PWM on frdm-k64f

Controlling a RGB led with PWM on frdm-k64f

roel0 — Thu, 24 Dec 2015 07:27:52 GMT

I have the frdm-k64f and the mbed application shield. On this shield there is a RGB led that I'm trying to control. However nothin happens. It looks like no pules is generated at all.

static inline void RGB_LED(uint32_t red, uint32_t green, uint32_t blue) {
    //FTM0_C5V = red;
    FTM0_C4V = green;
    FTM0_C7V = blue;
}

void frdm_as_led_init() {
    // Power on
    SIM_SCGC5 |= SIM_SCGC5_PORTC_MASK | SIM_SCGC5_PORTA_MASK;
    SIM_SCGC6 |= SIM_SCGC6_FTM0_MASK;
    //SIM_SOPT4 |= SIM_SOPT4_FTM0TRG0SRC(1);
    //NOTE: multiplexing port pat0 will cause cpu to hard fault on revision other then E
    // because it's also routed to the debugger
    //PORTA_PCR0 = PORT_PCR_MUX(3);  // FTM0_CH5
    PORTC_PCR4 = PORT_PCR_MUX(4);  // FTM0_CH4
    PORTA_PCR2 = PORT_PCR_MUX(3);  // FTM0_CH7
    RGB_LED(0,0,0);
    // Make write_protected registers writable
    FTM0_MODE |= FTM_MODE_WPDIS_MASK;
    FTM0_MODE &= ~ FTM_MODE_FTMEN_MASK;
    // Overflow at 99
    FTM0_MOD  = 99;
    FTM0_CNTIN = 0;
    FTM0_CNT = 0;
    FTM0_C4SC = FTM_CnSC_MSB_MASK | FTM_CnSC_ELSA_MASK | FTM_CnSC_ELSB_MASK;
    //FTM0_C5SC = FTM_CnSC_MSB_MASK | FTM_CnSC_ELSA_MASK;
    FTM0_C7SC = FTM_CnSC_MSB_MASK | FTM_CnSC_ELSA_MASK | FTM_CnSC_ELSB_MASK;
    FTM0_SC   = FTM_SC_CLKS(1) | FTM_SC_PS(7);     /* Edge Aligned PWM running from BUSCLK / 128 */
    RGB_LED(400,400,400);
}

Re: Controlling a RGB led with PWM on frdm-k64f

Alice_Yang — Fri, 25 Dec 2015 02:27:39 GMT

Hello ,

i think the CNT have not run up to 400 , when it up to 99, it overflow .

Hope it helps

Alice

Re: Controlling a RGB led with PWM on frdm-k64f

jeremyzhou — Fri, 25 Dec 2015 06:00:04 GMT

Hi Alice,

Alice pointed out the root cause of the issue, and you can find the more information about the value of the CnV setting affects the duty cycle of the PWM pulse in the reference manual.

http://cache.nxp.com/files/microcontrollers/doc/ref_manual/K64P144M120SF5RM.pdf?fpsp=1&WT_TYPE=Reference%20Manuals&WT_VE…
Have a great day,
Ping

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