topic Re: How to use PWM to control the brightness of LED lights? in Kinetis Microcontrollers

How to use PWM to control the brightness of LED lights?

codenoob — Tue, 12 Mar 2013 05:00:43 GMT

Sorry for asking this basic question. I am very new to this area. My board is KL05Z.

From the reference manual, the duty cycle is determined by "CnV". so I simply added the following lines to LED_Blink.c (before the while loop).

However, this did not work. When I run this piece of code in the board, it throws me to HardFault_Handler.

    TPM0_C0V = 1;
    TPM0_C1V = 1;
    TPM0_C2V = 1;
    TPM0_C3V = 1;
    TPM0_C4V = 1; 

  while(1)
  {
  Delay(200000);
  LED1_TOGGLE;
  Delay(200000);
  LED2_TOGGLE;
  Delay(200000);
  LED3_TOGGLE;
    }

What's the proper way of setting the duty cycles in PWM? I attached this piece of code in MKL05Z4.h, Hopefully it is easier for people with experience to look at.

Thanks a lot!

/** TPM - Peripheral register structure */
typedef struct TPM_MemMap {
  uint32_t SC;                                     /**< Status and Control, offset: 0x0 */
  uint32_t CNT;                                    /**< Counter, offset: 0x4 */
  uint32_t MOD;                                    /**< Modulo, offset: 0x8 */
  struct {                                         /* offset: 0xC, array step: 0x8 */
    uint32_t CnSC;                                   /**< Channel (n) Status and Control, array offset: 0xC, array step: 0x8 */
    uint32_t CnV;                                    /**< Channel (n) Value, array offset: 0x10, array step: 0x8 */
  } CONTROLS[6];
  uint8_t RESERVED_0[20];
  uint32_t STATUS;                                 /**< Capture and Compare Status, offset: 0x50 */
  uint8_t RESERVED_1[48];
  uint32_t CONF;                                   /**< Configuration, offset: 0x84 */
} volatile *TPM_MemMapPtr;

/* TPM - Register accessors */
#define TPM_SC_REG(base)                         ((base)->SC)
#define TPM_CNT_REG(base)                        ((base)->CNT)
#define TPM_MOD_REG(base)                        ((base)->MOD)
#define TPM_CnSC_REG(base,index)                 ((base)->CONTROLS[index].CnSC)
#define TPM_CnV_REG(base,index)                  ((base)->CONTROLS[index].CnV)
#define TPM_STATUS_REG(base)                     ((base)->STATUS)
#define TPM_CONF_REG(base)                       ((base)->CONF)




/* TPM - Register instance definitions */
/* TPM0 */
#define TPM0_SC                                  TPM_SC_REG(TPM0_BASE_PTR)
#define TPM0_CNT                                 TPM_CNT_REG(TPM0_BASE_PTR)
#define TPM0_MOD                                 TPM_MOD_REG(TPM0_BASE_PTR)
#define TPM0_C0SC                                TPM_CnSC_REG(TPM0_BASE_PTR,0)
#define TPM0_C0V                                 TPM_CnV_REG(TPM0_BASE_PTR,0)
#define TPM0_C1SC                                TPM_CnSC_REG(TPM0_BASE_PTR,1)
#define TPM0_C1V                                 TPM_CnV_REG(TPM0_BASE_PTR,1)
#define TPM0_C2SC                                TPM_CnSC_REG(TPM0_BASE_PTR,2)
#define TPM0_C2V                                 TPM_CnV_REG(TPM0_BASE_PTR,2)
#define TPM0_C3SC                                TPM_CnSC_REG(TPM0_BASE_PTR,3)
#define TPM0_C3V                                 TPM_CnV_REG(TPM0_BASE_PTR,3)
#define TPM0_C4SC                                TPM_CnSC_REG(TPM0_BASE_PTR,4)
#define TPM0_C4V                                 TPM_CnV_REG(TPM0_BASE_PTR,4)
#define TPM0_C5SC                                TPM_CnSC_REG(TPM0_BASE_PTR,5)
#define TPM0_C5V                                 TPM_CnV_REG(TPM0_BASE_PTR,5)
#define TPM0_STATUS                              TPM_STATUS_REG(TPM0_BASE_PTR)
#define TPM0_CONF                                TPM_CONF_REG(TPM0_BASE_PTR)
/* TPM1 */
#define TPM1_SC                                  TPM_SC_REG(TPM1_BASE_PTR)
#define TPM1_CNT                                 TPM_CNT_REG(TPM1_BASE_PTR)
#define TPM1_MOD                                 TPM_MOD_REG(TPM1_BASE_PTR)
#define TPM1_C0SC                                TPM_CnSC_REG(TPM1_BASE_PTR,0)
#define TPM1_C0V                                 TPM_CnV_REG(TPM1_BASE_PTR,0)
#define TPM1_C1SC                                TPM_CnSC_REG(TPM1_BASE_PTR,1)
#define TPM1_C1V                                 TPM_CnV_REG(TPM1_BASE_PTR,1)
#define TPM1_STATUS                              TPM_STATUS_REG(TPM1_BASE_PTR)
#define TPM1_CONF                                TPM_CONF_REG(TPM1_BASE_PTR)

Re: How to use PWM to control the brightness of LED lights?

codenoob — Tue, 12 Mar 2013 19:33:24 GMT

anybody who would like to help?

Re: How to use PWM to control the brightness of LED lights?

JimDon — Tue, 12 Mar 2013 19:40:27 GMT

You need to properly set up the TPM.

Create another project and use PE to set up the TPM for PWM.

Re: How to use PWM to control the brightness of LED lights?

codenoob — Tue, 12 Mar 2013 19:51:03 GMT

Hi Jim,

Thank you so much for your reply. I am a newbie so this might just be another ignorant question...

What does PE do that I can't do? My understanding is that I can just write code, build, program and the board would run. I imagine I can just add/edit code to set up the TPM, in my current code?

Thanks again.

Re: How to use PWM to control the brightness of LED lights?

JimDon — Tue, 12 Mar 2013 20:53:24 GMT

It "knows" how to write the code, If you know how to write the code, then no problem.

I recommend this because then you can look at the generated code and see how to do it.

I suppose I could post some code, but then I would deny you pleasure of learning.

BTW You are getting the hard fault because you did not set the clock gate in SIM_SCGC6.

Re: How to use PWM to control the brightness of LED lights?

adriansc — Wed, 13 Mar 2013 20:34:31 GMT

Hi,

You need to configure TPM as PWM and select a channel in this case One of the RGB led.

In the attachments you can find the code for a short application using TMP0 to change duty in RED led (PTB4 TPM0_CH1) Compare this code with yours and see what every register does.

Hope this helps.

Re: How to use PWM to control the brightness of LED lights?

victorrod — Fri, 17 May 2013 16:29:11 GMT

Hey Adrian,

Thanks for the help.

I read your code for TPM.

I am driving a relay by FET so GPIO output will be connected to FET.

The requirement is to have an ON/OFF button and when ON is pressed the Relay should be closed for 1 second and then opened for 9 seconds and repeat the loop 1000 times or until OFF is pressed.

I am wondering how your code will change and how the 'duty' will change?

Thanks

Victor

Re: How to use PWM to control the brightness of LED lights?

hunter18 — Wed, 03 Aug 2016 01:57:23 GMT

Hi Jim,

I want to make my led dim using tpm without using processor expert. Could you help me? i am new to kinetis world so i do not know where to start. BTW i'm using kl26z.

Thank You.

Regards,

Ken