MSP432E401Y: Wrong samples from 12-bit adc

Hi Johnson,

Thank you for your reply. I have the same sequence for the adc channels I have connected. The problem appears to originate in reading the values. As I want to trigger sampling from channel AIN0, read it and afterwards trigger a sample from AIN1 in the same step of the same sequencer. It is like the two channels are using the same spot, but I want their samples to be triggered at different times and independent of each other. So in my configuration I had, similar to yours becides: 

MAP_ADCSequenceStepConfigure(ADC0_BASE, 0, 0, ADC_CTL_CH0 | ADC_CTL_IE | ADC_CTL_END);
MAP_ADCSequenceStepConfigure(ADC0_BASE, 0, 0, ADC_CTL_CH1 | ADC_CTL_IE | ADC_CTL_END);

And before I read a sample I run the function for trigger:

MAP_ADCProcessorTrigger(ADC0_BASE, 0);

This is not working apparently. I think every time I read a value in---- void ADC0SS0_IRQHandler(void) ---  I read the sample only from the channel which is firstly configured to use this sequencer. Maybe I should use another sample sequencer for the second sampling. 

Hi Gerganna,

This code is trigger by PWM, thus attach the PWM code:

// Initiate PWM
void initPWM(void)
{
    /* The PWM peripheral must be enabled for use. */
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
    while(!(MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_PWM0)));

    /* Set the PWM clock to the system clock. */
    MAP_PWMClockSet(PWM0_BASE,PWM_SYSCLK_DIV_1);

    /* Enable the clock to the GPIO Port F, G and K for PWM pins */
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
    while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOF));
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOG);
    while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOG));
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOK);
    while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOK));

    /* Generator 1 Pins */
    MAP_GPIOPinConfigure(GPIO_PF2_M0PWM2);
    MAP_GPIOPinConfigure(GPIO_PF3_M0PWM3);

    /* Generator 2 Pins */
    MAP_GPIOPinConfigure(GPIO_PG0_M0PWM4);
    MAP_GPIOPinConfigure(GPIO_PG1_M0PWM5);

    /* Generator 3 Pins */
    MAP_GPIOPinConfigure(GPIO_PK4_M0PWM6);
    MAP_GPIOPinConfigure(GPIO_PK5_M0PWM7);

    MAP_GPIOPinTypePWM(GPIO_PORTF_BASE, (GPIO_PIN_2 | GPIO_PIN_3));
    MAP_GPIOPinTypePWM(GPIO_PORTG_BASE, (GPIO_PIN_0 | GPIO_PIN_1));
    MAP_GPIOPinTypePWM(GPIO_PORTK_BASE, (GPIO_PIN_4 | GPIO_PIN_5));

    /* Configure the PWM0 to count up/down without synchronization.
     * Note: Enabling the dead-band generator automatically couples the 2
     * outputs from the PWM block so we don't use the PWM synchronization. */
    MAP_PWMGenConfigure(PWM0_BASE, PWM_GEN_1, PWM_GEN_MODE_UP_DOWN | PWM_OUTPUT_MODE_SYNC_GLOBAL);
    MAP_PWMGenConfigure(PWM0_BASE, PWM_GEN_2, PWM_GEN_MODE_UP_DOWN | PWM_OUTPUT_MODE_SYNC_GLOBAL);
    MAP_PWMGenConfigure(PWM0_BASE, PWM_GEN_3, PWM_GEN_MODE_UP_DOWN | PWM_OUTPUT_MODE_SYNC_GLOBAL);

    /* Set the PWM period to 250Hz.  To calculate the appropriate parameter
     * use the following equation: N = (1 / f) * SysClk.  Where N is the
     * function parameter, f is the desired frequency, and SysClk is the
     * system clock frequency.
     * In this case you get: (1 / 250Hz) * 16MHz = 64000 cycles.  Note that
     * the maximum period you can set is 2^16 - 1.
     * TODO: modify this calculation to use the clock frequency that you are
     * using. */
    MAP_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1, PWM_LoadValue);
    MAP_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_2, PWM_LoadValue);
    MAP_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_3, PWM_LoadValue);

    // Clear cmpA
    MAP_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_2, 0);
    MAP_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_4, 0);
    MAP_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_6, 0);

    // Configure dead time
    MAP_PWMDeadBandEnable(PWM0_BASE, PWM_GEN_1, 160, 160);
    MAP_PWMDeadBandEnable(PWM0_BASE, PWM_GEN_2, 160, 160);
    MAP_PWMDeadBandEnable(PWM0_BASE, PWM_GEN_3, 160, 160);

    // Tirgger for ADC
    MAP_PWMGenIntTrigEnable(PWM0_BASE, PWM_GEN_2, PWM_TR_CNT_ZERO);

    /* Interrupt */
    MAP_IntMasterEnable();

    /* This timer is in up-down mode. Interrupts will occur when the counter counts up to 0. */
    MAP_PWMGenIntTrigEnable(PWM0_BASE, PWM_GEN_1, PWM_INT_CNT_ZERO);
    MAP_IntEnable(INT_PWM0_1);
    MAP_PWMIntEnable(PWM0_BASE, PWM_INT_GEN_1);

    /* Enable the PWM0 output signals
     *   Bit 2 (PF2) and Bit 3 (PF3)
     *   Bit 4 (PG0) and Bit 5 (PG1)
     *   Bit 6 (PK4) and Bit 7 (PK5) */
    MAP_PWMOutputState(PWM0_BASE, (  PWM_OUT_2_BIT | PWM_OUT_3_BIT |
                                     PWM_OUT_4_BIT | PWM_OUT_5_BIT |
                                     PWM_OUT_6_BIT | PWM_OUT_7_BIT ) , true);

    /* Enables the counter for a PWM generator block. */
    MAP_PWMGenEnable(PWM0_BASE, PWM_GEN_1);
    MAP_PWMGenEnable(PWM0_BASE, PWM_GEN_2);
    MAP_PWMGenEnable(PWM0_BASE, PWM_GEN_3);

    MAP_PWMSyncTimeBase(PWM0_BASE, (PWM_GEN_1_BIT | PWM_GEN_2_BIT | PWM_GEN_3_BIT));

    /* Update locally */
    MAP_PWMOutputUpdateMode(PWM0_BASE, ( PWM_OUT_1_BIT | PWM_OUT_2_BIT | PWM_OUT_3_BIT), PWM_OUTPUT_MODE_SYNC_GLOBAL);
}

After add this code, you will find you can enter ADC interrupt and gget the correct value.

Thanks!

Best Regards

Johnson

Hi, 

I understand but I want to make it work with a processo trigger. I do not use PWM in my application. 
Thank you any way.

Regards,

Gergana

Hi Gergana,

This code just as your refernece, you can change this code to match your requirement, The ADC module should normal.

And you can also refer to MSP432E SDK example code.

Thanks!

Best Regards

Johnson

I have one more question. If I need to sample from 3 different analog input channels and I only need to sample once from each channel and it is at different times, I can configure only one sequencer where sampling will occur. So I will have channel 0 to step 0, channel 1 to step 1, and channel 2 to step 2.

When I trigger sampling for analog input channel 2 can I get only samples for this channel ?  Or I need to always read values for all channels that are configured to sample in the same sample sequencer?

I want to use only ADC0 module and Sample Sequencer 0 which has buffer for 8 samples, for example.

Hi Gergana,

You can read the channel value you want directly, even if you configurate ADC to sequence mode.

There are some buffer inside ADC module, this will store all ADC capture value.

Thanks!

Best Regards

Johnson