TPM channel on K27

[attiliorossi321]

Good morning.

I'd like to use the TPM counter and its channel for some timing uses.

Prescale must be set at 128, so with a 24 mhz of bus clock I have 187, 5 Khz for tpm clock.

One channel (..ch2) must be set to get an interrupt break at every 1ms. I write the simple code that I use now.

It works properly for just 250 ms. After that, the TPM0 interrupt it does not work anymore and the output is fixed at one.

I don't understand this behavior. Probably something is missing in my code.

Look at CH2

Thanks in advance.

Attilio

#define        TPM_CHANNEL_0                0                                    // tpm channel 0 mask
#define        TPM_CHANNEL_1                1                                    // tpm channel 1 mask
#define        TPM_CHANNEL_2                2                                    // tpm channel 2 mask
#define        TPM_CHANNEL_3                3                                    // tpm channel 3 mask
#define        TPM_CHANNEL_4                4                                    // tpm channel 4 mask
#define        TPM_CHANNEL_5                5                                    // tpm channel 5 mask

#define        TPM_CH0_FLAG                0x01                                // channel 0 event flag
#define        TPM_CH1_FLAG                0x02                                // channel 1 event flag
#define        TPM_CH2_FLAG                0x04                                // channel 2 event flag
#define        TPM_CH3_FLAG                0x08                                // channel 3 event flag
#define        TPM_CH4_FLAG                0x10                                // channel 4 event flag
#define        TPM_CH5_FLAG                0x20                                // channel 5 event flag

#define        TPM_OVERFLOW_COUNTER        0x100                                // overflow counter flag

This the init function

void InitTimers(void)
{

    SIM->SCGC6 |= SIM_SCGC6_TPM0_MASK;                                           // clock gating
    SIM->SOPT2 |= SIM_SOPT2_TPMSRC(0x10);                                         // tpm clock source

    TPM0->SC  = TPM_SC_PS(0x07)    |                                                        // prescaler divide 0x07 = 128 times
                           TPM_SC_CMOD(0x01);                                                        // tpm increment every tpm counter clock

    TPM0->MOD = 46750;                                                                               // timer period

    // CHANNEL 2 SETTING
    TPM0->CONTROLS[TPM_CHANNEL_2].CnV  = 23375;                     // first int. after ~125ms
    TPM0->CONTROLS[TPM_CHANNEL_2].CnSC = (OUT_COMPARE_TOGGLE + TPM_CnSC_CHIE_MASK);        

    PORTA->PCR[5] = PORT_PCR_MUX(ALTERNATE_FUNCTION_3);      // PTA5 wired to out

    ConnectInterruptToCortex(TPM0_IRQn);                                                 // set TPM0 interrupt
}

This the interrupt

void TPM0_IRQHandler(void)
{
    UINT32     status;
    UINT32   l;

    status = TPM0->STATUS;

    // OVERFLOW
    if(status & TPM_OVERFLOW_COUNTER)
    {
    }

    // CH0
    if(status & TPM_CH0_FLAG)
    {
    }

    // CH1
    if(status & TPM_CH1_FLAG)
    {
    }

    // CH2
    if(status & TPM_CH2_FLAG)
    {
        l = TPM0->CNT;
        l = l + 376;
        l = l % 65535;

        TPM0->CONTROLS[TPM_CHANNEL_2].CnV = (UINT16)l;
    }

    // CH3
    if(status & TPM_CH3_FLAG)
    {
    }

    // CH4
    if(status & TPM_CH4_FLAG)
    {
    }

    // CH5
    if(status & TPM_CH5_FLAG)
    {
    }

    TPM0->STATUS |= status;

}

[winstinalaw415]

Exactly what I needed! You just saved me several hours. Thanks!

[Robin_Shen]

Hi Attilio,

I can see you configure the TPM0 work as OUT_COMPARE_TOGGLE mode.
Since you just need the ch2 get an interrupt break at every 1ms, why not direct configure TPM0->MOD let the period =1ms. Then the fixed TPM0->CONTROLS[TPM_CHANNEL_2].CnV value will always get 1ms interrupt and toggle waveform.(There is no need to modify ch2.CnV so frequently in IRQ)

Best Regards,

Robin

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[attiliorossi321]

Hi Robin.

Thanks for your interest.

You are right. But in reality the main purpose of this timer it's to generate a slow pwm frequency on channel 1.

So, I have to keep the MOD register at the desidered period. Usually it's 8 hz. (about 46875 value at 187,5 Khz).

But I wanted to use the same timer to get a 1 ms tick on another output.

Below, I send the total code that I'm using now, so may be more clear for you.

As I wrote the strange thing is at the beginning it works fine and properly. I can see the output toggle every 1ms (500 hz frequency) but suddendly afeter 250ms - 300 ms the TPM0 interrupt is no longer call.

Thanks

Attilio

void InitTimers(void)
{
    float     bus_tick, frequency, period, duty;
    UINT8    duty_cycle;

    /* TIMER 0 channels setting */
    GetLampParameters(&frequency, &duty_cycle);

    bus_tick = (1.0 / (BUSCLOCK / Power(2, 0x07)));
    period   = (1.0 / frequency) / bus_tick;
    duty     = (period / 100) * duty_cycle;

    SIM->SCGC6 |= SIM_SCGC6_TPM0_MASK;                                        // clock gating
    SIM->SOPT2 |= SIM_SOPT2_TPMSRC(0x10);                                    // tpm clock source

    TPM0->SC = 0x00UL;
    TPM0->SC |= TPM_SC_PS(0x07);                                            // prescaler divide 0x07 = 128 times
    TPM0->SC |= TPM_SC_CMOD(0x01);                                            // tpm increment every tpm counter clock

    TPM0->MOD = (UINT32)period;                                                // timer period

    // channel 1 setting
    TPM0->CONTROLS[TPM_CHANNEL_1].CnV  = (UINT32)duty;                        // timer duty cycle
    TPM0->CONTROLS[TPM_CHANNEL_1].CnSC = PWM_EDGE_ALIGN_HIGH_PULSE;            // pwm - no CHIE
    PORTA->PCR[4] = PORT_PCR_MUX(ALTERNATE_FUNCTION_3);                        // PTA4 wired to manage lamp

    // channel 2
    TPM0->CONTROLS[TPM_CHANNEL_2].CnSC = OUT_COMPARE_TOGGLE +\
                                         TPM_CnSC_CHIE_MASK;                                                 // ch2 - out.comp. - CHIE request

    TPM0->CONTROLS[TPM_CHANNEL_2].CnV  = 375;                                            // first match after ~2ms
    PORTA->PCR[5] = PORT_PCR_MUX(ALTERNATE_FUNCTION_3);                        // PTA5 wired to lamp

    ConnectInterruptToCortex(TPM0_IRQn);                                    // set TPM0 interrupt
}

void TPM0_IRQHandler(void)
{
            UINT32    status;
            UINT16    l;
    static UINT8     break_test;

    status = TPM0->STATUS;

    // OVERFLOW
    if(status & TPM_OVERFLOW_COUNTER)
    {
        break_test = 1;
    }

    // CH0
    if(status & TPM_CH0_FLAG)
    {
        break_test = 1;
    }

    // CH1
    if(status & TPM_CH1_FLAG)
    {
        break_test = 1;
    }

    // CH2
    if(status & TPM_CH2_FLAG)
    {
        l = TPM0->CNT;
        l = l + 375;
        TPM0->CONTROLS[TPM_CHANNEL_2].CnV = (UINT32)l;
    }

    // CH3
    if(status & TPM_CH3_FLAG)
    {
        break_test = 1;
    }

    // CH4
    if(status & TPM_CH4_FLAG)
    {
        break_test = 1;
    }

    // CH5
    if(status & TPM_CH5_FLAG)
    {
        break_test = 1;
    }

    TPM0->STATUS |= status;
}

[Robin_Shen]

Hi Attilio,

I find the value that you give CnV will greater than TPM0->MOD = 46750;

Please limit the value of CnV.

Best Regards,

Robin

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[attiliorossi321]

Robin thank you very much.

The solution was in front of me without seeing it.

Have a nice day.

Attilio