Tinkering TI MSP430F5529

Multiple Pulse Width Module (PWM) – TA0

Single PWM is useful for simple purposes but in many applications, we need multiple PWMs. In case of inverters, MOSFET/IGBT drives and bridges, there is no alternative other than to use multi-channel PWM. In this example, we will see how we can use multiple PWM to drive an RGB LED.

Code Example

#include "driverlib.h"
#include "delay.h"

#define steps 32

void clock_init(void);
void GPIO_init(void);
void timer_T0A5_init(void);

void main(void)
{
    unsigned char i = 0x00;

    const unsigned int duty1_value[steps] = {0, 
                                             6424, 
                                             12786, 
                                             19026, 
                                             25082, 
                                      30896, 
                                      36413, 
                                      41579, 
                                      46344, 
                                             50664,             
                                             54494, 
                                             57801, 
                                             60550, 
                                             62716, 
                                             64278,                                                
                                             65220, 
                                             65534, 
                                             65218, 
                                             64272, 
                                             62708, 
                                             60540,
                                             57788, 
                                             54480, 
                                             50647, 
                                             46326, 
                                             41558, 
                                             36391, 
                                             30873, 
                                             25057, 
                                             19000, 
                                             12760, 
                                             6397};

    const unsigned int duty2_value[steps] = {57801, 
                                             60550, 
                                             62716, 
                                             64278,                                                
                                             65220, 
                                             65534, 
                                             65218, 
                                             64272, 
                                             62708, 
                                             60540,
                                             57788, 
                                             54480, 
                                             50647, 
                                             46326, 
                                             41558, 
                                             36391, 
                                             30873, 
                                             25057, 
                                             19000, 
                                             12760, 
                                             6397, 
                                             0, 
                                             6424, 
                                             12786, 
                                             19026, 
                                             25082, 
                                      30896, 
                                      36413, 
                                      41579, 
                                      46344, 
                                             50664,             
                                             54494};

    const unsigned int duty3_value[steps] = {57788, 
                                             54480, 
                                             50647, 
                                             46326, 
                                             41558, 
                                             36391, 
                                             30873, 
                                             25057, 
                                             19000, 
                                             12760, 
                                             6397, 
                                             0, 
                                             6424, 
                                             12786, 
                                             19026, 
                                             25082, 
                                      30896, 
                                      36413, 
                                      41579, 
                                      46344, 
                                             50664,             
                                             54494,
                                             57801, 
                                             60550, 
                                             62716, 
                                             64278,                                                
                                             65220, 
                                             65534, 
                                             65218, 
                                             64272, 
                                             62708, 
                                             60540};

    WDT_A_hold(WDT_A_BASE);

    clock_init();
    GPIO_init();
    timer_T0A5_init();

    while(true)
    {
        for(i = 0; i < steps; i++)
        {
            Timer_A_setCompareValue(TIMER_A0_BASE,
                                    TIMER_A_CAPTURECOMPARE_REGISTER_1,
                                    duty1_value[i]);

            Timer_A_setCompareValue(TIMER_A0_BASE,
                                    TIMER_A_CAPTURECOMPARE_REGISTER_2,
                                    duty2_value[i]);

            Timer_A_setCompareValue(TIMER_A0_BASE,
                                    TIMER_A_CAPTURECOMPARE_REGISTER_3,
                                    duty3_value[i]);

            delay_ms(250);
        }
    };
}

void clock_init(void)
{
    PMM_setVCore(PMM_CORE_LEVEL_3);

    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P5,
                                               (GPIO_PIN4 | GPIO_PIN2));

    GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P5,
                                                (GPIO_PIN5 | GPIO_PIN3));

    UCS_setExternalClockSource(XT1_FREQ,
                               XT2_FREQ);

    UCS_turnOnXT2(UCS_XT2_DRIVE_4MHZ_8MHZ);

    UCS_turnOnLFXT1(UCS_XT1_DRIVE_0,
                    UCS_XCAP_3);

    UCS_initClockSignal(UCS_MCLK,
                        UCS_XT2CLK_SELECT,
                        UCS_CLOCK_DIVIDER_1);

    UCS_initClockSignal(UCS_SMCLK,
                        UCS_XT2CLK_SELECT,
                        UCS_CLOCK_DIVIDER_1);

    UCS_initClockSignal(UCS_ACLK,
                        UCS_XT1CLK_SELECT,
                        UCS_CLOCK_DIVIDER_1);
}

void GPIO_init(void)
{
    GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P1,
                                                (GPIO_PIN2 + GPIO_PIN3 + GPIO_PIN4));
}

void timer_T0A5_init(void)
{
    Timer_A_initCompareModeParam CompareModeParam1 = {0};
    Timer_A_initCompareModeParam CompareModeParam2 = {0};
    Timer_A_initCompareModeParam CompareModeParam3 = {0};

    Timer_A_initContinuousModeParam ContinuousModeParam = {0};

    ContinuousModeParam.clockSource = TIMER_A_CLOCKSOURCE_SMCLK;
    ContinuousModeParam.clockSourceDivider = TIMER_A_CLOCKSOURCE_DIVIDER_1;
    ContinuousModeParam.timerClear = TIMER_A_DO_CLEAR;
    ContinuousModeParam.timerInterruptEnable_TAIE = TIMER_A_TAIE_INTERRUPT_DISABLE;
    ContinuousModeParam.startTimer = false;

    CompareModeParam1.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam1.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam1.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_1;
    CompareModeParam1.compareValue = 0;

    CompareModeParam2.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam2.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam2.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_2;
    CompareModeParam2.compareValue = 0;

    CompareModeParam3.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam3.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam3.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_3;
    CompareModeParam3.compareValue = 0;

    Timer_A_initCompareMode(TIMER_A0_BASE,
                            &CompareModeParam1);

    Timer_A_initCompareMode(TIMER_A0_BASE,
                            &CompareModeParam2);

    Timer_A_initCompareMode(TIMER_A0_BASE,
                            &CompareModeParam3);

    Timer_A_initContinuousMode(TIMER_A0_BASE,
                               &ContinuousModeParam);

    Timer_A_startCounter(TIMER_A0_BASE,
                         TIMER_A_CONTINUOUS_MODE);
}

Hardware Setup

Explanation

Multi-PWM example here uses the same concepts as in the single PWM example. This time timer TA0 is used and the following pins are set for PWM output:

GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P1,
                                            (GPIO_PIN2 + GPIO_PIN3 + GPIO_PIN4));

Note that this timer has 5 CC channels associated with it but we are using only three of them since we have connected an RGB LED to these pins.

4MHz XT2CLK source feeds SMCLK which in turn is used to run timer TA0. Thus, timer TA0 is operating at 4MHz speed.

UCS_initClockSignal(UCS_SMCLK, UCS_XT2CLK_SELECT, UCS_CLOCK_DIVIDER_1);

Timer PWM setup is not very much different. The only differences are timer mode, the number of channels and their individual settings.

void timer_T0A5_init(void)
{
    Timer_A_initCompareModeParam CompareModeParam1 = {0};
    Timer_A_initCompareModeParam CompareModeParam2 = {0};
    Timer_A_initCompareModeParam CompareModeParam3 = {0};

    Timer_A_initContinuousModeParam ContinuousModeParam = {0};

    ContinuousModeParam.clockSource = TIMER_A_CLOCKSOURCE_SMCLK;
    ContinuousModeParam.clockSourceDivider = TIMER_A_CLOCKSOURCE_DIVIDER_1;
    ContinuousModeParam.timerClear = TIMER_A_DO_CLEAR;
    ContinuousModeParam.timerInterruptEnable_TAIE = TIMER_A_TAIE_INTERRUPT_DISABLE;
    ContinuousModeParam.startTimer = false;

    CompareModeParam1.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam1.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam1.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_1;
    CompareModeParam1.compareValue = 0;

    CompareModeParam2.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam2.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam2.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_2;
    CompareModeParam2.compareValue = 0;

    CompareModeParam3.compareInterruptEnable = TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE;
    CompareModeParam3.compareOutputMode = TIMER_A_OUTPUTMODE_RESET_SET;
    CompareModeParam3.compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_3;
    CompareModeParam3.compareValue = 0;

    Timer_A_initCompareMode(TIMER_A0_BASE, &CompareModeParam1);

    Timer_A_initCompareMode(TIMER_A0_BASE, &CompareModeParam2);

    Timer_A_initCompareMode(TIMER_A0_BASE, &CompareModeParam3);

    Timer_A_initContinuousMode(TIMER_A0_BASE, &ContinuousModeParam);

    Timer_A_startCounter(TIMER_A0_BASE, TIMER_A_CONTINUOUS_MODE);
}

Unlike in the previous PWM example, timer TA0 is set for continuous mode of operation and so the top PWM count value is 65535. Thus, the period of the PWMs is about 16 ms. No interrupt is used. We just have to setup each channel individually and then run the timer in continuous mode.

In the main loop, PWMs of each channel are altered and the effect is visible in the form of RGB LED’s changing colour.

for(i = 0; i < steps; i++)
{
     Timer_A_setCompareValue(TIMER_A0_BASE,
                             TIMER_A_CAPTURECOMPARE_REGISTER_1,
                             duty1_value[i]);

     Timer_A_setCompareValue(TIMER_A0_BASE,
                             TIMER_A_CAPTURECOMPARE_REGISTER_2,
                             duty2_value[i]);

     Timer_A_setCompareValue(TIMER_A0_BASE,
                             TIMER_A_CAPTURECOMPARE_REGISTER_3,
                             duty3_value[i]);

     delay_ms(250);
}

The duty cycle of each PWM channel is coded to in a half-sine wave pattern but each of them has a different phase shift from the other.

const unsigned int duty3_value[steps] = {57788, 
                                         54480, 
                                         50647, 
                                         46326, 
                                         41558, 
                                         36391, 
                                         30873, 
                                         25057, 
                                         19000, 
                                         12760, 
                                         6397, 
                                         0, 
                                         6424, 
                                         12786, 
                                         19026, 
                                         25082, 
                                         30896, 
                                         36413, 
                                         41579, 
                                         46344, 
                                         50664,             
                                         54494,
                                         57801, 
                                         60550, 
                                         62716, 
                                         64278,                                                
                                         65220, 
                                         65534, 
                                         65218, 
                                         64272, 
                                         62708, 
                                         60540};

When combined with the three LEDs of the RGB, this creates a beautiful rhythmic color pattern.

Demo

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