FTM0 PWM on MK20DX256

DustyStew — Mon, 30 Mar 2020 01:28:55 GMT

I'm using a Teensy 3.1 with MK20DX256 MCU.

I'm writing to the metal (not using Teensy libraries).

I can't seem to get PWM working. I think I need a basic example for FTM0. My code below.

TIA

My init code for the FTM0:

#define PWM_PERIOD 10000

SIM_SCGC6 |= SIM_SCGC6_FTM0; // clock to flex timer 0

FTM0_SC = 0; // stop clocking the counter

dummy = FTM0_FMS; // enable write to all FTM registers

FTM0_MODE = FTM_MODE_WPDIS; // disable write protection

FTM0_MODE = FTM_MODE_WPDIS | FTM_MODE_FTMEN;

FTM0_PWMLOAD = 0x02ff; // enable loading of compare values for every channel

FTM0_CNTIN = 0; // counter initial value

FTM0_CNT = 0; // counter

FTM0_MOD = PWM_PERIOD - 1; // wrap value ie counter modulo

FTM0_SC = 0x08; // no ISR, up-count, enabled system clock, prescale=1

To enable a particular pin, this code is called:

switch(pin)

{

case PTC1:

PORTC_PCR1 = (uint32_t)(PORT_PCR_MUX(4) | PORT_PCR_DSE | PORT_PCR_SRE); // FTM0, teensy 22

GPIOC_PDDR |= 0x00000002;

FTM0_C0SC = 0x28;

break;

case PTC2:

PORTC_PCR2 = (uint32_t)(PORT_PCR_MUX(4) | PORT_PCR_DSE | PORT_PCR_SRE); // teensy 23

GPIOC_PDDR |= 0x00000004;

FTM0_C1SC = 0x28;

break;

case PTC3:

PORTC_PCR3 = (uint32_t)(PORT_PCR_MUX(4) | PORT_PCR_DSE | PORT_PCR_SRE); // teensy 9

GPIOC_PDDR |= 0x00000008;

FTM0_C2SC = 0x28;

break;

case PTC4:

PORTC_PCR4 = (uint32_t)(PORT_PCR_MUX(4) | PORT_PCR_DSE | PORT_PCR_SRE); // teensy 10

GPIOC_PDDR |= 0x00000010;

FTM0_C3SC = 0x28;

break;

case PTD4:

PORTD_PCR4 = (uint32_t)(PORT_PCR_MUX(4)); // teensy 6

GPIOD_PDDR |= 0x00000010;

FTM0_C4SC = 0x28;

break;

case PTD5:

// uA_tx('E');

PORTD_PCR5 = (uint32_t)(PORT_PCR_MUX(4)); // teensy 20

GPIOD_PDDR |= 0x00000020;

FTM0_C5SC = 0x28;

break;

case PTD6:

PORTD_PCR6 = (uint32_t)(PORT_PCR_MUX(4)); // teensy 21

GPIOD_PDDR |= 0x00000040;

FTM0_C6SC = 0x28;

break;

case PTD7:

PORTD_PCR7 = (uint32_t)(PORT_PCR_MUX(4)); // teensy 5

GPIOD_PDDR |= 0x00000080;

FTM0_C7SC = 0x28;

}

To set PWM duty cycle value using a 16 bit variable value:

switch(pin)

{

case PTC1: FTM0_C0V = value; break; // FTM0, teensy 22 pin 44

case PTC2: FTM0_C1V = value; break; // teensy 23 pin 45

case PTC3: FTM0_C2V = value; break; // teensy 9

case PTC4: FTM0_C3V = value; break; // teensy 10

case PTD4: FTM0_C4V = value; break; // teensy 6

case PTD5: FTM0_C5V = value; break;//uA_tx('V');break; // teensy 20 pin 62

case PTD6: FTM0_C6V = value; break; // teensy 21 pin 63

case PTD7: FTM0_C7V = value; break; // teensy 5

}

Re: FTM0 PWM on MK20DX256

jingpan — Wed, 01 Apr 2020 09:41:06 GMT

Hi Thomas,

I tested your code. It has no problem in register setting. It only need to put duty setting and pin selection code before start.

It should looks like

PWM_Pin_sel(PTD7); //your second function
PWM_duty(PTD7,PWM_PERIOD/2); // third function
FTM0_SC = 0x08;

K20 72M version hasn't SDK. But K20 100M device has. The SDK has lots of FTM example. Since FTM module is same, you can refer to those example.

Regards,

Jing

topic FTM0 PWM on MK20DX256 in Kinetis Microcontrollers

FTM0 PWM on MK20DX256

Re: FTM0 PWM on MK20DX256