CCS/TMS320F28335: Abnormal graph waveform

Dear Gautam:

I use the official example routine at: C:\ti\controlSUITE\device_support\f2833x\v142\DSP2833x_examples_ccsv5\adc_seqmode_test

Below is the source code:

#include "DSP28x_Project.h" // Device Headerfile and Examples Include File

// ADC start parameters
#if (CPU_FRQ_150MHZ) // Default - 150 MHz SYSCLKOUT
#define ADC_MODCLK 0x3 // HSPCLK = SYSCLKOUT/2*ADC_MODCLK2 = 150/(2*3) = 25.0 MHz
#endif
#if (CPU_FRQ_100MHZ)
#define ADC_MODCLK 0x2 // HSPCLK = SYSCLKOUT/2*ADC_MODCLK2 = 100/(2*2) = 25.0 MHz
#endif
#define ADC_CKPS 0x1 // ADC module clock = HSPCLK/2*ADC_CKPS = 25.0MHz/(1*2) = 12.5MHz
#define ADC_SHCLK 0xf // S/H width in ADC module periods = 16 ADC clocks
#define AVG 1000 // Average sample limit
#define ZOFFSET 0x00 // Average Zero offset
#define BUF_SIZE 2048 // Sample buffer size

// Global variable for this example
Uint16 SampleTable[BUF_SIZE];

main()
{
Uint16 i;

// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the DSP2833x_SysCtrl.c file.
InitSysCtrl();

// Specific clock setting for this example:
EALLOW;
SysCtrlRegs.HISPCP.all = ADC_MODCLK; // HSPCLK = SYSCLKOUT/ADC_MODCLK
EDIS;

// Step 2. Initialize GPIO:
// This example function is found in the DSP2833x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio(); // Skipped for this example

// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
DINT;

// Initialize the PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the DSP2833x_PieCtrl.c file.
InitPieCtrl();

// Disable CPU interrupts and clear all CPU interrupt flags:
IER = 0x0000;
IFR = 0x0000;

// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example. This is useful for debug purposes.
// The shell ISR routines are found in DSP2833x_DefaultIsr.c.
// This function is found in DSP2833x_PieVect.c.
InitPieVectTable();

// Step 4. Initialize all the Device Peripherals:
// This function is found in DSP2833x_InitPeripherals.c
// InitPeripherals(); // Not required for this example
InitAdc(); // For this example, init the ADC

// Specific ADC setup for this example:
AdcRegs.ADCTRL1.bit.ACQ_PS = ADC_SHCLK;
AdcRegs.ADCTRL3.bit.ADCCLKPS = ADC_CKPS;
AdcRegs.ADCTRL1.bit.SEQ_CASC = 1; // 1 Cascaded mode
AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0x0;
AdcRegs.ADCTRL1.bit.CONT_RUN = 1; // Setup continuous run

// Step 5. User specific code, enable interrupts:

// Clear SampleTable
for (i=0; i<BUF_SIZE; i++)
{
SampleTable[i] = 0;
}

// Start SEQ1
AdcRegs.ADCTRL2.all = 0x2000;

// Take ADC data and log the in SampleTable array
for(;;)
{
for (i=0; i<AVG; i++)
{
while (AdcRegs.ADCST.bit.INT_SEQ1== 0) {} // Wait for interrupt
AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1;
SampleTable[i] =((AdcRegs.ADCRESULT0>>4) );
}
}
}

F.F,

That appears to work on my setup.  Can you try with a DC signal first to make sure it works as expected?  Then start with a slow frequency (like 2Hz) and see if there's an input frequency where the graph stops working.

-Tommy

Dear Tommy:

Below is the wave of 2Hz, 100Hz and 1.1KHz. And the 1KHz sine wave is the same as the previous one. I have no idea about those phenomena. Can you give me some reminders?

1, 2Hz

2, 100Hz

3, 1.1KHz

Wish for your reply.

Best Regards

F.F,

It looks as though your device may not be running at the expected frequency.  You can check the ADC sampling rate in the example by toggling a pin like GPIO31, which also happens to control the LD2 LED on the controlCARD.

Please modify the example with the following:

Configure GPIO31 to be an output by adding this between the "Clear SampleTable" loop and "Start SEQ1" instruction:

    EALLOW;
    GpioCtrlRegs.GPAMUX2.bit.GPIO31 = 0;  // GPIO31 = GPIO31
    GpioCtrlRegs.GPADIR.bit.GPIO31 = 1;   // GPIO31 = output
    EDIS;

Then toggle GPIO31 in your ADC sampling loop by adding this after the INT_SEQ1_CLR bit is set:

    GpioDataRegs.GPATOGGLE.bit.GPIO31 = 1;

You can expect to see a square wave of about 368kHz using an oscilloscope on GPIO31 of the docking station.  The LED should appear to be on.

-Tommy