TM4C123GH6PM: Problem during simulatenously sampling using both the ADCs

Part Number: TM4C123GH6PM

I intend to sample two incoming input signals using both the ADCs in the the board. I want to sample both of them simulatenously without any jitter. Is there any effective method to do so? If so, can you suggest me something and provide me some kind of reference code?

No such example exists but you can take a look at using ADC_TRIGGER_WAIT and ADC_TRIGGER_SIGNAL. See below. In you ADC0, configure a sample sequencer for the first signal and trigger it with the processor using the ADC_TRIGGER_WAIT flag. In your ADC1 configure a sample sequencer for the second signal and trigger with the processor using the ADC_TRIGGER_SIGNAL flag. Try it and see if it works and share with the community your working code. 

The uDMA can be used on both ADCs. It is used to read the results. To get simultaneous conversions you need to start both ADCs at the same time, but it is not necessary to read the results at the same time. The uDMA will read the results sequentially.

Ralph previously posted an example of using a timer to trigger the ADC and using uDMA to read the results.

//*****************************************************************************
//
// project0.c - Example to demonstrate minimal TivaWare setup
//
// Copyright (c) 2012-2017 Texas Instruments Incorporated.  All rights reserved.
// Software License Agreement
// 
// Texas Instruments (TI) is supplying this software for use solely and
// exclusively on TI's microcontroller products. The software is owned by
// TI and/or its suppliers, and is protected under applicable copyright
// laws. You may not combine this software with "viral" open-source
// software in order to form a larger program.
// 
// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
// DAMAGES, FOR ANY REASON WHATSOEVER.
// 
// This is part of revision 2.1.4.178 of the EK-TM4C123GXL Firmware Package.
//
//*****************************************************************************

#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "inc/hw_adc.h"
#include "inc/hw_types.h"
#include "inc/hw_udma.h"
#include "driverlib/debug.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "driverlib/adc.h"
#include "driverlib/udma.h"
#include "driverlib/timer.h"
#include "driverlib/rom.h"
#include "driverlib/rom_map.h"
#include "driverlib/systick.h"
#include "utils/uartstdio.h"
//*****************************************************************************
//
// Define pin to LED color mapping.
//
//*****************************************************************************

//*****************************************************************************
//
//! \addtogroup example_list
//! <h1>Project Zero (project0)</h1>
//!
//! This example demonstrates the use of TivaWare to setup the clocks and
//! toggle GPIO pins to make the LED's blink. This is a good place to start
//! understanding your launchpad and the tools that can be used to program it.
//
//*****************************************************************************



//*****************************************************************************
//
// The error routine that is called if the driver library encounters an error.
//
//*****************************************************************************
#ifdef DEBUG
void
__error__(char *pcFilename, uint32_t ui32Line)
{
}
#endif

//*****************************************************************************
//
// Main 'C' Language entry point.  Toggle an LED using TivaWare.
//
//*****************************************************************************
uint32_t adcbuffer[1000];
uint32_t adcdata1[1000];
uint32_t adcdata2[1000];
uint32_t i,timebase,triglvl,xpos,res0,res1;


void main(){


    SysCtlClockSet(SYSCTL_SYSDIV_10 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); //20 MHz clock

    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);

        GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
        GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_2);
        GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1);
        GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_4);

        ADCSequenceDisable(ADC0_BASE, 3);



    //Timer Configuration
    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);


     TimerConfigure(TIMER0_BASE,TIMER_CFG_PERIODIC);

    TimerLoadSet(TIMER0_BASE, TIMER_A,12);          //set the timer to fs=2 ksps load value

                                                         //if timer loading value=5000; fs=1 ksps
                                                         // sysclock=20mhz so tsys=1/2000000sec;to get 1ms delay
                                                         //we need to load timer with 1ms/0.5us

      TimerEnable(TIMER0_BASE, TIMER_A);









           // ADCSequenceDisable(ADC0_BASE, 3);
           // ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL, 266);


            ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
            ADCSequenceConfigure(ADC1_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);

            ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH7 | ADC_CTL_IE | ADC_CTL_END);
            ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH6 | ADC_CTL_IE | ADC_CTL_END);
            ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH5 | ADC_CTL_IE | ADC_CTL_END);
            ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH4 | ADC_CTL_IE | ADC_CTL_END);
            ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH3 | ADC_CTL_IE | ADC_CTL_END);

            ADCSequenceEnable(ADC0_BASE, 3);
            ADCSequenceEnable(ADC1_BASE, 3);

            ADCIntClear(ADC0_BASE, 3);


        while(1)
        {
            ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH5 | ADC_CTL_IE | ADC_CTL_END);
            ADCIntClear(ADC1_BASE, 3);
            ADCProcessorTrigger(ADC1_BASE, 3);                  // Trigger the ADC conversion.
            while(!ADCIntStatus(ADC1_BASE, 3, false)){}         // Wait for conversion to be completed.
            ADCIntClear(ADC1_BASE, 3);                      // Clear the ADC interrupt flag.
            ADCSequenceDataGet(ADC1_BASE, 3, adcbuffer);                // Read ADC Value.
            timebase = adcbuffer[0];

            ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH4 | ADC_CTL_IE | ADC_CTL_END);
            ADCIntClear(ADC1_BASE, 3);
            ADCProcessorTrigger(ADC1_BASE, 3);                  // Trigger the ADC conversion.
            while(!ADCIntStatus(ADC1_BASE, 3, false)){}             // Wait for conversion to be completed.
            ADCIntClear(ADC1_BASE, 3);                      // Clear the ADC interrupt flag.
            ADCSequenceDataGet(ADC1_BASE, 3, adcbuffer);                // Read ADC Value.
            triglvl = adcbuffer[0];

            ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH3 | ADC_CTL_IE | ADC_CTL_END);
            ADCIntClear(ADC0_BASE, 3);
            ADCProcessorTrigger(ADC0_BASE, 3);                  // Trigger the ADC conversion.
            while(!ADCIntStatus(ADC0_BASE, 3, false)){}             // Wait for conversion to be completed.
            ADCIntClear(ADC0_BASE, 3);                      // Clear the ADC interrupt flag.
            ADCSequenceDataGet(ADC0_BASE, 3, adcbuffer);                // Read ADC Value.
            xpos = adcbuffer[0];

            for (i=0;i<=1000;i++)
            {
                ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH7 | ADC_CTL_IE | ADC_CTL_END);
                ADCIntClear(ADC0_BASE, 3);
                ADCProcessorTrigger(ADC0_BASE, 3);              // Trigger the ADC conversion.
                while(!ADCIntStatus(ADC0_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCIntClear(ADC0_BASE, 3);                  // Clear the ADC interrupt flag.
                ADCSequenceDataGet(ADC0_BASE, 3, adcbuffer);            // Read ADC Value.
                adcdata1[i] = adcbuffer[0];
                res0=adcdata1[i];
            //  GPIOPinWrite(GPIO_PORTF_BASE,GPIO_PIN_1, res0);

                ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH6 | ADC_CTL_IE | ADC_CTL_END);
                ADCIntClear(ADC1_BASE, 3);
                ADCProcessorTrigger(ADC1_BASE, 3);              // Trigger the ADC conversion.
                while(!ADCIntStatus(ADC1_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCIntClear(ADC1_BASE, 3);                  // Clear the ADC interrupt flag.
                ADCSequenceDataGet(ADC1_BASE, 3, adcbuffer);            // Read ADC Value.
                adcdata2[i] = adcbuffer[0];
                res1=adcdata2[i];
               //GPIOPinWrite(GPIO_PORTF_BASE,GPIO_PIN_4, res1);
            }
        }
}
















.

Thankyou Sir. I was able to sample using both the ADCs. This is my current code. But I am observing distortion in the sampled signals and I am unable to figure out the reason.

Update: Sir, I was able to get an approximate reconstructed signal but I am getting delay between two output of the ADC. Is there any way I could minimise the delay between both outputs? Because currently I am getting significant delay between the two.

You setup the timer, but then used "ADCProcessorTrigger()" in your loop, and you did not use "ADC_TRIGGER_WAIT". For simple CPU trigger of simultaneous conversions the sequence is more like this:

                ADCProcessorTrigger(ADC0_BASE, 3 | ADC_TRIGGER_WAIT); // Setup the trigger but wait.
                ADCProcessorTrigger(ADC1_BASE, 3);                    // Trigger both ADC's
                while(!ADCIntStatus(ADC0_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCSequenceDataGet(ADC0_BASE, 3, &adcdata1[i]);            // Read ADC Value.
                while(!ADCIntStatus(ADC1_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCSequenceDataGet(ADC1_BASE, 3, &adcdata2[i]);            // Read ADC Value.

Sir, I have used this in the for loop but the values stored
 in adcdata1 and adcdata2 is becoming zero now.
 I am unable see any conversion.

ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH7 | ADC_CTL_IE | ADC_CTL_END);
                ADCSequenceStepConfigure(ADC1_BASE, 3, 0, ADC_CTL_CH6 | ADC_CTL_IE | ADC_CTL_END);
                ADCIntClear(ADC0_BASE, 3);
                ADCIntClear(ADC1_BASE, 3);
                ADCProcessorTrigger(ADC0_BASE, 3 | ADC_TRIGGER_WAIT); // Setup the trigger but wait.
                ADCProcessorTrigger(ADC1_BASE, 3);                    // Trigger both ADC's
                while(!ADCIntStatus(ADC0_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCSequenceDataGet(ADC0_BASE, 3, &adcdata1[i]);            // Read ADC Value.
                adcdata1[i] = adcbuffer[0];
                while(!ADCIntStatus(ADC1_BASE, 3, false)){}         // Wait for conversion to be completed.
                ADCSequenceDataGet(ADC1_BASE, 3, &adcdata2[i]);            // Read ADC Value.
                adcdata2[i] = adcbuffer[0];

Update: I was able to do the simultaneous sampling. But when I used 3.3V as the reference voltage(DC), theoretically I expected a straightline around 4100 in the graphy but I see a straight line around 500. I cannot determine the problem for this.