FLEXPWM EXT_SYNC

Motafared — Sun, 01 Jun 2025 09:40:49 GMT

I am Trying to create 8 synced PWM using IMXRT1062 on TEENSY4 board
I created master PWM to sync them to it using XBAR and EXT_SYNC
i could build the PWM easily but i couldn't send the the trigger from the master pwm to the others
i tested it between different modules but everytime i fail ,The slave PWM keep counting to the end of its 16 bit counter without receiving EXT_SYNC signal and then wrap again from zero
i even tried to send the trigger signal to external physical pin as a debugging but i could not see it on the scope
can any one help me what i messed
i am using ARDUINO IDE

// ====== FLEXPWM2 Setup: PWM2_0_A on Pin 4 slave======

// Enable clock for FLEXPWM2 (CG9: bits 19-18)

CCM_CCGR4 |= (3 << 18); // FLEXPWM2 for Pin 4 (PWM2_0_A)

// Set pin 4 to ALT1 = FLEXPWM2_PWM0_A

CORE_PIN4_CONFIG = 1;

FLEXPWM2_MCTRL &= ~(FLEXPWM_MCTRL_RUN(1 << 0)); //stop it at the begining

FLEXPWM2_SM0CTRL2 = FLEXPWM_SMCTRL2_INDEP|FLEXPWM_SMCTRL2_INIT_SEL(3); //independent + init select = EXT_SYNC

FLEXPWM2_SM0CTRL = FLEXPWM_SMCTRL_PRSC(0) | FLEXPWM_SMCTRL_FULL;

FLEXPWM2_SM0INIT = 0;

FLEXPWM2_SM0VAL0 = 0;

FLEXPWM2_SM0VAL1 = 0;

FLEXPWM2_SM0VAL2 = 0+PHASE;

FLEXPWM2_SM0VAL3 = (DUTY+PHASE);

FLEXPWM2_OUTEN |= FLEXPWM_OUTEN_PWMA_EN(1 << 0);

FLEXPWM2_MCTRL |= FLEXPWM_MCTRL_LDOK(1 << 0);

FLEXPWM2_MCTRL |= FLEXPWM_MCTRL_RUN(1 << 0);

//FLEXPWM3_PWM1 MASTER

uint32_t freq_kHz = 500;

// Enable clock for FLEXPWM3 (CG9: bits 20-21)

CCM_CCGR4 |= (3 << 20);

//enable clock for xbar1

CCM_CCGR2 |= CCM_CCGR2_XBAR1(CCM_CCGR_ON);

// VAL1 determines frequency

uint32_t M = IPG_CLOCK_HZ / (freq_kHz * 1000);

// Configure PWM3 SM1 as EXT_SYNC generator

FLEXPWM3_MCTRL &= ~(FLEXPWM_MCTRL_RUN(1 << 1));

FLEXPWM3_SM1CTRL2 = FLEXPWM_SMCTRL2_INDEP;

FLEXPWM3_SM1CTRL = FLEXPWM_SMCTRL_PRSC(0) | FLEXPWM_SMCTRL_FULL;

FLEXPWM3_SM1INIT = 0;

FLEXPWM3_SM1VAL0 = 0;

FLEXPWM3_SM1VAL1 = M;

FLEXPWM3_SM1VAL2 = 0;

FLEXPWM3_SM1VAL3 = M/2;

FLEXPWM3_SM1VAL5 = M/2;

// Enable OUT_TRIG1 on VAL1 match

FLEXPWM3_SM1TCTRL = (uint16_t)(1 << 1); // OUT_TRIG_EN bit 1 = PWM_OUT_TRIG1 on VAL1 match

// Route FLEXPWM3_SM1_OUT_TRIG1:XBAR1_IN48 → XBARA1_OUT_FLEXPWM2_PWM0_EXT_SYNC 44

XBARA1_SEL22 &= 0xff00; //Clear the SEL44 fields

XBARA1_SEL22 |= 48; ///

FLEXPWM3_OUTEN |= FLEXPWM_OUTEN_PWMB_EN(1 << 1);

FLEXPWM3_MCTRL |= FLEXPWM_MCTRL_LDOK(1 << 1);

FLEXPWM3_MCTRL |= FLEXPWM_MCTRL_RUN(1 << 1);

Re: FLEXPWM EXT_SYNC

EdwinHz — Mon, 02 Jun 2025 19:58:17 GMT

Hi @Motafared,

I highly recommend you download MCUXpresso and try the pwm example codes we provide with the i.MX RT1060 SDK for more information on how to achieve this setup.

Re: FLEXPWM EXT_SYNC

Motafared — Tue, 03 Jun 2025 19:27:43 GMT

I found the problem

The submodules in all register names are 0 indexd submodule 0,1,2,3

But in the table of xbar inputs for output trigger they are 1 indexed

So if you are working with submodule 0 and you want to assign its output trigger to xbar1 you should choose

FLEXPWM1_PWM1_OUT_TRIG0 or

FLEXPWM1_PWM1_OUT_TRIG1

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