FTM PWM - no output

[tomášpilný]

Hello everone,

I'am using MK60N512VMD100 on custom board, with CW v10.6.

I'm having problems with FTM PWM output. At this stage I'm just trying to figure out what will work for me and how to set everything properly. With the code given below I'm not getting any output on expected pin. I've just hooked it up to LED with resistor just to see if it outputs ANYTHING - and it doesn't. At this moment I'm in school measuring the output and it seems to be the same for any combination of MOD, CnV and PS:

MOD	CnV	PS	period	pulse width
FFFF	FFFF	0	20 ms	10 ms
FFFF	F	0	20 ms	10 ms
FFFF	F	7	20 ms	10 ms

And so on. My conclusion is that the PWM signal is not getting through. Can you see where the problem might be ? What have I forgot ? :smileygrin:

Thanks

Tom

	SIM_SCGC5 |= SIM_SCGC5_PORTA_MASK; // enable clock for PTA
	SIM_SCGC6 |= SIM_SCGC6_FTM0_MASK; // enable clock for FTM0
	//Edit registers when no clock is fed to timer so the MOD value, gets pushed in immediately
	FTM0_SC = 0; // Make sure its Off!
	PORTA_PCR6 |= PORT_PCR_MUX(3); // FTM0 CH3 minerva 25
	GPIOA_PDDR |= (1 << 6); // set as output

	FTM0_MODE |= FTM_MODE_WPDIS_MASK; // disable write protection
	FTM0_MODE |= FTM_MODE_FTMEN_MASK; // FTM0 enable
	FTM0_CNT = 0; // counter initialization
	FTM0_MOD = FTM_MOD_MOD(0xFFFF);
	FTM0_CNTIN = 0;

FTM0_C3SC = 0x20; // edge aligned PWM MSB = 1

FTM0_C3V = 0xFFFF; // when the CNT reaches this value -> FTM does what CnSC tells (clear)

FTM0_CONF |= FTM_CONF_BDMMODE(3); // run in debug mode

	FTM0_SC |= FTM_SC_CLKS(0x01); // Select the system clock => turn on the FTM

[xiangjun_rong · Accepted solution]

Hi, I think your code has something wrong, anyway, the FTM0_C3V register value should be less than the FTM0_MOD so that PWM can output a low-high interleaved signal, unfortunately, you set both FTM0_C3V and FTM0_MOD as 0xFFFF; that is why you get the constant logic on the FTM channel.

Pls update the code as:

FTM0_C3SC = 0x28; //MSB:MSA=10, ESB:ESA=10,high low

    FTM0_MOD = FTM_MOD_MOD(0xFFFF);

FTM0_C3V = 0x7FFF; // when the CNT reaches this value -> FTM does what CnSC tells (clear)

pls have a try.

BR

XiangJun Rong

[mjbcswitzerland]

Tom

Below is code showing how to set up a PWM signal on the output that you are interested in.

This is API code:

PWM_INTERRUPT_SETUP pwm_setup;
pwm_setup.int_type = PWM_INTERRUPT;
pwm_setup.pwm_mode = (PWM_SYS_CLK | PWM_PRESCALER_16); // clock PWM timer from the system clock with /16 pre-scaler
pwm_setup.pwm_reference = (_TIMER_0 | 3); // timer module 0, channel 3
pwm_setup.pwm_frequency = PWM_TIMER_US_DELAY(TIMER_FREQUENCY_VALUE(1000), 16);// generate 1000Hz on PWM output
pwm_setup.pwm_value   = _PWM_PERCENT(20, pwm_setup.pwm_frequency); // 20% PWM (high/low)
fnConfigureInterrupt((void *)&pwm_setup); // enter configuration for PWM test

and this is the low level code that performs the actual work (I have also noted the HEX values that are actually written to the FTM registers)

POWER_UP(6, SIM_SCGC6_FTM0); // ensure that the FlexTimer module is powered up
_CONFIG_PERIPHERAL(A, 6, (PA_6_FTM0_CH3 | PORT_SRE_FAST | PORT_DSE_HIGH)); // FTM0_CH3 on PA.6 (alt. function 3)
ptrFlexTimer->FTM_channel[ucChannel].FTM_CSC = FTM_CSC_MS_ELS_PWM_HIGH_TRUE_PULSES; // FTM0_C3SC = 0x28
ptrFlexTimer->FTM_CNTIN = 0;
ptrFlexTimer->FTM_MOD = (ptrPWM_settings->pwm_frequency - 1); // set the PWM period - valid for all channels [0xc34]
ptrFlexTimer->FTM_channel[ucChannel].FTM_CV = ptrPWM_settings->pwm_value; // set the duty cycle for the particular channel [0x271]
ptrFlexTimer->FTM_SC = (ptrPWM_settings->pwm_mode & PWM_MODE_SETTINGS_MASK); // note that the mode is shared by all channels in the flex timer [0x0c]

Finally here is screen shot of the FTM registers after the configuration so that you can compare with yours and seen if there is something missing or different:

Regards

Mark

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