Setting up FlexTimer on MK20DX256VMD10

[derekdrost]

Hello,

     I am trying to set up PWM on the above processor using the FlexTimer.

     I've attempted to use the code from this thread:

          K60 FlexTimer (PWM) Example Code?

     With this code I get 3 outputs turning on.

Thank you,

Derek

[soledad · Accepted solution]

Hi Derek

The FlexTimer (FTM) on Kinetis MCU is built upon a very simple timer, HCS08 Timer PWM Module (TPM), used for many years on Freescale 8-bit microcontrollers. The FTM extends the functionality of TPM to meet demands of motor control applications. A simple PWM code can be as simple as shown below:

/*Using FTM2_CH0 FTM2_CH1 output PWM with 90% high, 10% low wave*/

void FTM_EPWM(void)

{

PORTA_PCR10 = (0|PORT_PCR_MUX(3)); /* FTM2_CH0 enable on PTA10 */

PORTB_PCR18 = (0|PORT_PCR_MUX(3)); /* FTM2_CH0 enable on PTB18 */

PORTA_PCR11 = (0|PORT_PCR_MUX(3)); /* FTM2_CH1 enable on PTA11 */

PORTB_PCR19 = (0|PORT_PCR_MUX(3)); /* FTM2_CH1 enable on PTB19 */

FTM2_MOD = 0x0063;  /* 0x0063 / 25MHz = 4uS PWM period */

      /* Configure timers for edge aligned PWM High True Pulses */

      printf("FTM2_ Edge_Aligned Test 1\r\n");

      printf("Please check the waveform, 90% Hign Ture EPWM\r\n");

      FTM2_C0SC = 0x28;   /* No Interrupts; High True pulses on Edge Aligned PWM */

      FTM2_C1SC = 0x28; 

      FTM2_C0V = 0x005A;  /* 90% pulse width */

      FTM2_C1V = 0x005A; 

      FTM2_SC = 0x08;     /* Edge Aligned PWM running from BUSCLK / 1 */

}

Are you using MQX???

Have a great day,
Sol

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[derekdrost]

Thank you for the reply,

     Yes I am using MQX 4.0.

     I used your code, replacing your pins with the correct ones in my case.

     However, I get directed to the kernel interrupt handler with the following line:

     FTM2_MOD = 0x0063;  /* 0x0063 / 25MHz = 4uS PWM period */

Any thoughts?

[soledad]

hi,

If you are using MQX then it is necessary to be careful in case interrupts are needed for FTM application. There are two ways to add user interrupts into an MQX system - kernel_isr or MQX managed isr.

Kernel_isr is fast but it bypasses MQX, thus, no MQX API function can be called from such a kernel_isr.

MQX managed isr is slower, as it runs dispatcher in case a higher priority task becomes ready during isr.

Attached you can find an example using interrupts, you can use this, in order to develop your own application

Have a great day,
Sol

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[derekdrost]

Soledad,

     I guess I'm more interested in why this line doesn't work. Curious, why do you use FTM2, when in most of the examples I see around the internet use FTM0?

Cheers,

Derek

[derekdrost]

Never mind, got it working =) thank you for the help!

[davidtietz]

Derek,

What did you do to get this working? I am having a similar issue.

Thanks!