Jim Wall

Can't get PWM to work on a iMX283

Discussion created by Jim Wall on Jan 16, 2012
Latest reply on Jan 16, 2012 by Jim Wall

I am in the process of writing a bootlet for a custom board with an iMX283. I need a 10kHz PWM line to charge a voltage ladder but when I try to get it working, I only see one  transition on the PWM line going from high to low.

It is if I don't have the XTAL oscillator gated through to the PWM circuitry.

Has any one successfully gotten PWM to work?

I did notice that the PWM_CLK24M was gated off by default so I gated that through but still don't seem to have a clock.

Here is a code snipet of my fuction that sets up the PWM channel. along with





       mxs_iomux_setup_pad(BACKLIGHT_POWER  | MXS_PAD_12MA | MXS_PAD_3V3 );
       printf("\r\nHW_CLKCTRL_XTAL = %X\r\n",HW_CLKCTRL_XTAL_RD());
       printf("\r\nMUXSEL7 = %X\n\r",HW_PINCTRL_MUXSEL7_RD());

// we need to setup the PWM channel
// for 10kHz pulses to charge the
// voltage tripler

        HW_PWM_ACTIVEn_SET(4,0x000004b0); //1200 ticks for 50% duty cycle
        HW_PWM_PERIODn_SET(4,0x000b095e); // 2400-1 ticks for period

        printf("\r\nACTIVE = %X\r\n",HW_PWM_ACTIVEn_RD(4));
        printf("PERIOD = %X\r\n",HW_PWM_PERIODn_RD(4));
        printf("PWM_CTRL = %X\r\n",HW_PWM_CTRL_RD());


Here is the output of the above code:

HW_CLKCTRL_XTAL = 00000001


ACTIVE = 000004B0
PERIOD = 000B095E
PWM_CTRL = 3FC00010


Any help would be appreciated. Thanks in advance.