TWR-K21F120MA Input Capture

[aniketmarkande]

Need code for Input Capture. Please help if anybody has written it.

[aniketmarkande]

Hi xiangjun,

Thank you for quick reply. It was very helpful, but in current project we are using kinetis SDK API. I want to know which API's to use and in what order for input capture.

[xiangjun_rong]

Hi, Aniket

Of course, the SDK2.0 include the capture function, I copy it here which is included in fsl_ftm.c and fsl_ftm.h loctaed at:

C:\Freescale\SDK2.0_FRDM_K22F\devices\MK22F51212\drivers

You can follow up the procedure:

1)enable FTM clock with the function CLOCK_EnableClock(kCLOCK_Ftm0); //assume you use FTM0 and FTM0_CH0 as input pin.

2)set up pin assigmnet, FTM0_CH0 is multiplexed with PTA0 for 121 pin mapbga package

    CLOCK_EnableClock(kCLOCK_PortA);
     PORT_SetPinMux(PORTB, 0U, kPORT_MuxAlt4);

3)initializing FTM0 module:

ftm_config_t ftmInfo;

    FTM_GetDefaultConfig(&ftmInfo);
        FTM_Init(FTM0, &ftmInfo);

    FTM_EnableInterrupts(FTM0, kFTM_Chnl0InterruptEnable);
    NVIC_EnableIRQ(FTM0_IRQn);

   FTM_SetupInputCapture(FTM0,0,kFTM_RisingEdge,0);

4)In the ISR of FTM0, ckecking the FTM_GetStatusFlags(FTM0), if the kFTM_Chnl0Flag is set, you can read the FTM0_C0V register.

Note I do not test the above code, pls have a try.

Hope it can help you

BR

XiangJun Rong

void FTM_SetupInputCapture(FTM_Type *base,
                           ftm_chnl_t chnlNumber,
                           ftm_input_capture_edge_t captureMode,
                           uint32_t filterValue)
{
    uint32_t reg;

    reg = base->CONTROLS[chnlNumber].CnSC;
    reg &= ~(FTM_CnSC_MSA_MASK | FTM_CnSC_MSB_MASK | FTM_CnSC_ELSA_MASK | FTM_CnSC_ELSB_MASK);
    reg |= captureMode;

    /* Set the requested input capture mode */
    base->CONTROLS[chnlNumber].CnSC = reg;
    /* Input filter available only for channels 0, 1, 2, 3 */
    if (chnlNumber < kFTM_Chnl_4)
    {
        reg = base->FILTER;
        reg &= ~(FTM_FILTER_CH0FVAL_MASK << (FTM_FILTER_CH1FVAL_SHIFT * chnlNumber));
        reg |= (filterValue << (FTM_FILTER_CH1FVAL_SHIFT * chnlNumber));
        base->FILTER = reg;
    }
#if defined(FSL_FEATURE_FTM_HAS_ENABLE_PWM_OUTPUT) && (FSL_FEATURE_FTM_HAS_ENABLE_PWM_OUTPUT)
    /* Set to input mode */
    FTM_SetPwmOutputEnable(base, chnlNumber, false);
#endif
}

[xiangjun_rong]

Hi, Aniket,

From hardware perspective, you can connected the tested low frequency signal to the FTM_CHn, it is okay, Once the edge of tested signal is detected, an interrupt is triggered, the FTM_CNT is loaded into the FTM_CnV reg automatically. In the capture ISR, you can read the FTM_CnV register.

I attach a capture example based on KE02, hope it can help you. In your application code, you can add the code to select the FTM_CHn pin.

BR

Xiangjun Rong