VREF PINS ON F28379D VER 2.0 ?

Hi Christian,

The F28379 Launchpad already has an onboard 3v buffered reference for VREFHI. The DAC can be configured to use this 3v reference by setting DACREFSEL=1.

Christian,

What pins on the Launchpad are you probing? Did you confirm in the watch window that DACREFSEL == 1 and DACVALS == 2048?

Hi Frank,

I am probing the pin 30 on j3 ( DACOUT A - ADCINA0).

As advised, I changed reference_vdac for reference vref

Follow below the code:

//
// Included Files
//
#include "F28x_Project.h"

//
// Globals
//
volatile struct DAC_REGS* DAC_PTR[4] = {0x0,&DacaRegs,&DacbRegs,&DaccRegs};
Uint16 dacval = 2048;

//
// Defines
//
#define REFERENCE_VDAC 0
#define REFERENCE_VREF 1
#define DACA 1
#define DACB 2
#define DACC 3
#define REFERENCE REFERENCE_VREF
#define DAC_NUM DACA

//
// Function Prototypes
//
void configureDAC(Uint16 dac_num);

void main(void)
{
//
// Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2837xD_SysCtrl.c file.
//
InitSysCtrl();

//
// 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 F2837xD_PieCtrl.c file.
//
InitPieCtrl();

//
// Clear all interrupts and initialize PIE vector table:
//
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();

//
// Configure DAC
//
configureDAC(DAC_NUM);

while(1)
{
DAC_PTR[DAC_NUM]->DACVALS.all = dacval;
DELAY_US(2);
}
}

//
// configureDAC - Configure specified DAC output
//
void configureDAC(Uint16 dac_num)
{
EALLOW;
DAC_PTR[dac_num]->DACCTL.bit.DACREFSEL = REFERENCE;
DAC_PTR[dac_num]->DACOUTEN.bit.DACOUTEN = 1;
DAC_PTR[dac_num]->DACVALS.all = 0;
DELAY_US(10); // Delay for buffered DAC to power up
EDIS;
}

//
// End of file
//

Christian,

That's odd. This is a simple example and with those settings, you should see 1.5V on J3/30. Do you get any errors when you build the example and/or load the code to the Launchpad? What is the exact voltage you are reading?

Also, this might seem rudimentary but if you are using a scope to check the voltage, make sure it's not set to 50ohms.

Hi Frank,

Yes, I use a scope to check the voltage , but with a resistor of 25 Ohms.

DACOUTUO Values:

dac a = 400mV
dac b =400 mV
dac c = I could not locate this pin.

Regards,

I don't know if you meant in series or 25 Ohms to ground. The dac can't drive any resistance lower than 5K well. Can you please double check the voltage with a multimeter?

25 ohm resistor is in series.

Do you suggest to place the multimeter in series too to double check and increase the value of the resistor in serie?

Regards,

Hi

Is there a way to use the DAC1, 2, 3, 4 as DACOUT ? As I could read your reply in this previous post     that those are PWMDACs. I understand that I can turn a PWM into DAC, right ?

The issue you are facing is a bit odd. It's possible you have a bad Launchpad. A few more points/questions before we make that conclusion.

1. Did you make any hardware modifications to the Launchpad?
2. The 25ohm series resistor shouldn't make much difference but for the purposes of debug, please remove it and retest.
3. Also please take a picture of the Launchpad with all connections and as much annotations for the connections as you can.

DAC1, 2, 3, 4 are PWMDACs. I see you created another post for it that's been answered.

Hi Christian,

Can you reply to the previous inquiry or if your issue is resolved, kindly let us know.