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TM4C123GH6PM: Using different PWM generators for pin PB6, PB7

can altineller
Expert 1760 points

Part Number: TM4C123GH6PM

Hello,

Currently I am obtaining 2 independent PWM signals from pin PB6 and PB7 using single PWM generator, such as:


    MAP_SysCtlPWMClockSet(SYSCTL_PWMDIV_8);
    ui32PWMClock = ui32SysClkFreq / PWM_DIV;
    ui32Load = (ui32PWMClock / PWM_FRQ) - 1;

    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);

    MAP_GPIOPinConfigure(GPIO_PB6_M0PWM0);
    MAP_GPIOPinConfigure(GPIO_PB7_M0PWM1);

    MAP_GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_6);
    MAP_GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_7);

    MAP_PWMGenConfigure(PWM0_BASE, PWM_GEN_0, PWM_GEN_MODE_UP_DOWN | PWM_GEN_MODE_NO_SYNC);
    MAP_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_0, ui32Load);

    MAP_PWMGenEnable(PWM0_BASE, PWM_GEN_0);
    MAP_PWMOutputState(PWM0_BASE, PWM_OUT_0_BIT | PWM_OUT_1_BIT, true);

Right now, I am using count up down strategy to obtain 2 different PWM signals, from single generator.

Can I use different PWM generators on pin PB6 and PB7? So I can take advantage of pwm sync, and other features? Or would I have to rewire my board and use a different pin for the second pwm generator.

Best Regards,

Can

  • 0
    TI__Guru**** 191886 points

    Hi Can,

    can altineller said:
    Can I use different PWM generators on pin PB6 and PB7? So I can take advantage of pwm sync, and other features? Or would I have to rewire my board and use a different pin for the second pwm generator.

      That is not possible. As you can see, only generator 0 is associated with PB6/PB7. No other generators are associated with these two pins. You will need to use different pins for the second PWM generator. 

  • 0 in reply to Charles Tsai
    Expert 1760 points

    Hello Charles Tsai,

    Yes, I noticed that PB6 and PB7 are associated with generator 0, and tried to use D0 as secondary PWM output. Here is the relevant part of my code now:

        uint32_t ui32SysClkFreq = MAP_SysCtlClockGet();

    uint8_t PWM_DIV = 8;
    uint16_t PWM_FRQ_A = 10;
    uint16_t PWM_FRQ_B = 10;

    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);

    MAP_SysCtlPWMClockSet(SYSCTL_PWMDIV_8);

    uint32_t ui32PWMClock = ui32SysClkFreq / PWM_DIV;

    uint32_t ui32LoadA = (ui32PWMClock / PWM_FRQ_A) - 1;
    uint32_t ui32LoadB = (ui32PWMClock / PWM_FRQ_B) - 1;

    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM1);

    MAP_GPIOPinConfigure(GPIO_PB6_M0PWM0);
    MAP_GPIOPinConfigure(GPIO_PD0_M1PWM0);

    MAP_GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_6);
    MAP_GPIOPinTypePWM(GPIO_PORTD_BASE, GPIO_PIN_0);

    MAP_PWMGenConfigure(PWM0_BASE, PWM_GEN_0, PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
    MAP_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_0, ui32LoadA);

    MAP_PWMGenConfigure(PWM1_BASE, PWM_GEN_0, PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
    MAP_PWMGenPeriodSet(PWM1_BASE, PWM_GEN_0, ui32LoadB);

    MAP_PWMGenEnable(PWM0_BASE, PWM_GEN_0);
    MAP_PWMOutputState(PWM0_BASE, PWM_OUT_0_BIT, true);

    MAP_PWMGenEnable(PWM1_BASE, PWM_GEN_0);
    MAP_PWMOutputState(PWM1_BASE, PWM_OUT_0_BIT, true);

    // send zero pwm
    MAP_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_0, 6000);
    MAP_PWMPulseWidthSet(PWM1_BASE, PWM_OUT_0, 3000);

    However, I am not getting independent pwm signals, indeed, I am getting, same output from pins PB6 and PD0, with the PWM signals overlapped. If I change the duty cycle of the second PWM generator, the parts at the top of the pwm signal change in duty, almost as I am summing them.

    So, my question is reduced to: how can I generate 2 independent pwm signals on tm4c123, with from 2 different modules.

    Best Regards,

    Can

  • 0 in reply to can altineller
    Expert 1760 points

    answering my own question: PD0 and PB6 are connected with a 0ohm resistor on the launchpad, hence why the pwm's overlap. removing the resistor enabled me to have two different generators, running at different frequencies.

    best regarrds,

    can